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It was once called Nipéhe, an ancient village site of the Nez Perce Tribe. Located at the confluence of Rock Creek and the lower Salmon River in western Idaho, this spot also saw bands of Paleoindians sojourneying here thousands of years ago. Long since abandoned as a modern world has moved in, it is today called Cooper’s Ferry, a location known to few. But this place has acquired a very special meaning to a team of archaeologists and student volunteers led by Loren Davis of Oregon State University. They have been excavating here for ten years, and the results of their efforts have been nothing less than remarkable: during the last two years, they discovered lithic artifacts (stone tools) in the lowest excavation layers—radiocarbon-dated to between 15,280 and 16,560 years ago. Thus far, the deposits have revealed hundreds of objects, including stone tools; fire-cracked rock; charcoal; and animal bone fragments, including tooth fragments from an extinct species of horse that lived in North America at the end of the last glaciation. Most significantly, according to Davis, Cooper’s Ferry is the “oldest radiocarbon-dated site in North America that includes artifacts associated with the bones of extinct animals”.*

Because of the age of the findings,  Davis and the team are suggesting some tantalizingly specific implications about how and when humans settled North America. “Early peoples moving south along the Pacific coast would have encountered the Columbia River as the first place below the glaciers where they could easily walk and paddle in to North America,” said Davis. “Essentially, the Columbia River corridor was the first off-ramp of a Pacific coast migration route. The timing and position of the Cooper’s Ferry site is consistent with and most easily explained as the result of an early Pacific coastal migration.”*

Coopers Ferry is also included among a small but growing number of sites across the Americas that are revealing evidence of human occupation significantly before 13,000 years ago, the time when the Clovis culture, long thought to have been the most ancient Paleoindian culture in the Americas, emerged. 

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Cooper’s Ferry site excavations in progress in 2018. Loren Davis, Oregon State University

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About 2,000 miles due east of Cooper’s Ferry, Devlin Gandy, an archaeologist from St. John’s College at the University of Cambridge, dons a hazmat suit, multiple hairnets, and a respirator and proceeds to incise into a vertical profile of sediment with a scalpel to extract a cube of an ancient deposit before placing it carefully into a centrifuge vial. The sediment cube sample comes from what has been dubbed the “deep hole”, consisting of some of the earliest and deepest excavated cultural layers within the famous site of Meadowcroft Rockshelter, located within a remote forested area of the western Pennsylvania Appalachian region. Meadowcroft is long known to have produced evidence of what some scientists arguably suggest to be the earliest presence of humans in North America — an occupation that goes back at least 16,000 years ago. The purpose of the sampling, among other things, is to test the possible presence of human DNA still remaining in the soil, left there by human occupiers who may have lived and worked there at that early time. The sampling was sent to the Centre for Geogenetics in Copenhagen, Denmark, where, at this writing, they are being systematically tested. 

“The site remains as one of the first serious challenges to the formerly prevailing Clovis First model and also clearly indicates that among the first inhabitants of the New World were broad-spectrum foragers rather than focused big game hunters,” says James Adovasio, the archaeologist who led excavations at the site.  “The early assemblage from Meadowcroft is now seen to have analogs at Cactus Hill, Virginia, as well as several sites on the Delmarva Peninsula of Maryland.”

Adovasio makes clear that he is not hanging his hat on the sample testing results. “We stress that the absence of any human, animal, or plant DNA in no way undermines previous conclusions about the site,” he emphasizes. The archaeological investigations have historically churned up too much other data to be overturned by any new, single sampling. Moreover, investigations are not finished. “More than one-third of the site remains unexcavated,” Adovasio adds. But there are no plans to conduct on-site investigations in the immediate future.

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Above and below: Collecting the deposit sampling within the Meadowcroft Rockshelter for testing . Courtesy James Adovasio

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Across North and South America — north, south, east, and west — a new narrative is emerging about the discovery of artifacts and other finds that are radically re-shaping the traditional paradigm of the early settling of the Americas. What follows is a consolidation of major feature articles that have appeared in Popular Archaeology over the past few years, stories that are helping to inform a complex new narrative. 

*Archaeological site reveals humans arrived in the Americas more than 16,000 years ago, Aug. 29, 2019. American Association for the Advancement of Science.  https://popular-archaeology.com/article/archaeological-site-reveals-humans-arrived-in-the-americas-more-than-16000-years-ago/

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Exploring Early Americans at Friedkin, and More

By Michael Gordon

Excavations at the 15,000-year-old Friedkin site in 2016. Image courtesy Michael R. Waters and Center for the Study of the First Americans, Texas A&M University

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Few had ever heard of the little town of Buttermilk Creek, Texas, until it was placed on the map in early 2011 when Texas A&M University anthropologist Michael Waters made his public announcement. He and a team of archaeologists, researchers, students and volunteers had been painstakingly excavating at an archaeological site, known as the Debra L. Firiedkin site, for years. What they discovered there had generated excitement in the world of American archaeology. 

Yielding a prolific assemblage of artifacts, the Buttermilk Creek Complex, as researchers are now calling it, contained evidence of small blades, choppers and scrapers, implements made by people who had long departed the scene, long before any notion in the minds of the early European explorers that anyone had ever inhabited the North American continent.

“Most of these are chipping debris from the making and resharpening of tools,” said Waters, “but over 50 are tools. There are bifacial artifacts that tell us they were making projectile points and knives at the site. There are expediently made tools and blades that were used for cutting and scraping.”

On the face of it, his discovery could hardly eclipse any of the finds made by other archaeologists through decades of excavation and research about the early peopling of the Americas. But there were several important differences that made the site, and the finds, unique. They had to do with the sheer number of the finds, their nature, and the dating, with the most sensational difference being the dating.  

“What is special about the Debra L. Friedkin site is that it has the largest number of artifacts dating to the pre-Clovis time period, that these artifacts show an array of different technologies, and that these artifacts date to a very early time,” said Waters.

The Clovis time refers to a time period (beginning about 13,500 years ago) to which, according to many scholars, the earliest known stone tools and weapons made by early ancestral Native Americans could be assigned. Best known for their medium to large fluted lanceolate projectile points and distinctive bone and ivory items, these stone artifact finds constitute the evidential basis for the widely accepted “Clovis First” hypothesis, which suggests that the people associated with the artifacts were the first inhabitants of the Americas. Clovis artifacts have been found in abundance at sites across the North American continent. 

But the headline-making finds at the Friedkin site were not Clovis, and they were older than the oldest known Clovis tools by about 2,000 years.

Waters and his associates used Optically Stimulated Luminescence (OSL) dating, a technique that measures the amount of light energy trapped over thousands of years in minerals within the sediment surrounding artifacts. Professor Steven Forman of the University of Illinois at Chicago worked with Waters at the site, collecting 50 core samples from two sites at Buttermilk Creek for testing. “We found Buttermilk Creek to be about 15,500 years ago — a few thousand years before Clovis” said Forman. “We dated the sediments by a variety of optical methods. We also dated different mineral fractions as well, and we consistently got the same ages. We looked at the age structure of the sediment by many different ways and got the same answers.”  

In addition to providing compelling evidence for pushing the clock back on when the earliest Americans arrived, the Friedkin site findings have provided additional credence to the suggestion that the stone tool technology of the Clovis culture was not imported into the Americas via the Bering Land Bridge (“Beringia”) in accordance with the Clovis Model, but instead evolved in North America from an earlier technology. Given the nature and characteristics of the Buttermilk Creek Complex, Waters maintains that the Complex represents a “type of assemblage from which the Clovis assemblage could emerge” with the new dating providing “ample time for people to settle into the environments of North America, colonize South America by at least ~14.1 to 14.6 ka, develop the Clovis tool kit, and create a base population through which Clovis technology could spread”.[1]

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Some of the artifacts from the 15,500-year-old horizon. Image courtesy Michael R. Waters.

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The Mounting Evidence

The arguments against the traditional Clovis First perspective point to the fact that no Clovis-type artifacts have been found in Northeast Asia, from where the early Americans under the Clovis Model are suggested to have migrated, and fluted stone points that are iconic for Clovis and found in Alaska are all dated too late to be assigned to the Clovis horizon. Moreover, six major sites in South America with stratigraphic layers dated to the Clovis period are devoid of Clovis period artifacts. 

Nevertheless, comparing the evidence of Clovis technology dated to very early occupation of the Americas with what is available for the same time period for other technology forms had traditionally given Clovis the decided edge in the debate. But new evidence against Clovis has been mounting. The Friedkin site is not the only site that has been dated to the pre-Clovis time period. Pre-Clovis finds have been recorded at sites such as Pedra Furada in Brazil, Monte Verde in Chile, two mammoth kill sites in Wisconsin, Topper in South Carolina, Cactus Hill and Saltville in Virginia, and Meadowcroft in Pennsylvania, among others. The evidence at these sites, however, has been in dispute and is not as robust as that found at Friedkin.

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Excavators examine a cluster on the proposed pre-Clovis surface at the Topper site. Courtesy Center for the Study of the First Americans.

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Proposed pre-Clovis artifacts found at the Topper site.  Courtesy Center for the Study of the First Americans.

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Proposed pre-Clovis bend break tools found at the Topper site.  Courtesy Center for the Study of the First Americans.

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But new discoveries have emerged and joined Friedkin with stronger evidence of pre-Clovis beginnings…….

At the Paisley caves in south-central Oregon, a team of research scientists led by Dennis L. Jenkins of the University of Oregon’s Museum of Natural and Cultural History found evidence that an early stone implement technology, known as “Western Stemmed” projectile points (darts or thrusting spearheads), were manufactured at least 11,070 to 11,340 radiocarbon years ago, making them concurrent with or possibly earlier than the Clovis culture (dated to 13,000 calendar years ago). The researchers obtained 190 radiocarbon dates on artifacts, human coprolites (dried feces), bones and sagebrush twigs within layers of silt deposited over thousands of years in the  caves. The broad, concave-based, fluted Clovis projectile points often associated with early Americans who lived about 12,000 – 13,000 years ago were not found in the caves. 

Past studies of the Paisley Caves have also reported very early dates from human coprolites with ancient DNA, but questions arose about whether those samples could have been contaminated, and whether they were found in true context with artifacts from the same era. So the researchers did an exhaustive examination of the stratigraphy, which is one of Loren Davis’ specialties. Davis was a member of the archaeological team investigating Paisley.

“We continued to excavate Paisley Caves from 2009 through 2011,” the authors wrote in Science. “To resolve the question of stratigraphic integrity, we acquired 121 new AMS [accelerator mass spectrometry] radiocarbon dates on samples of terrestrial plants, macrofossils from coprolites, bone collagen and water soluble extracts recovered from each of these categories. To date, a total of 190 radiocarbon dates have been produced from the Paisley Caves.”

Davis conducted microscopic analysis of the soil using a “petrographic” microscope, to eliminate any indications that liquid – such as water or urine from humans or animals –  may have moved down from higher layers into the lower layers, thus “contaminating” or compromising the integrity of the dating of the soil. They also analyzed the silt where the stem points were found and bracketed above and below those layers to determine if the radiocarbon dates synchronized.

The result: “The stemmed points were in great context,” Davis said. “There is no doubt that they were in primary context, associated with excellent radiocarbon dates.” The new dating was valid and few could now argue with the results.

The significance of the Paisley finds extends from the fact that Western Stemmed points and Clovis points differ fundamentally in terms of their hafting portions, the part of the stone point that connects to a shaft. Stemmed points are narrower or constricted at their bases, whereas the hafting portions of Clovis points are not narrow, but thinned width-wise through removal of large flakes from their bases. 

“These two approaches to making projectile points were really quite different,” Davis said, “and the fact that Western Stemmed point-makers fully overlap, or even pre-date Clovis point makers likely means that Clovis peoples were not the sole founding population of the Americas.”

“From our dating, it appears to be impossible to derive Western Stemmed points from a proto-Clovis tradition,” Jenkins said. “It suggests that we may have here in the Western United States a tradition that is at least as old as Clovis, and quite possibly older. We seem to have two different traditions co-existing in the United States that did not blend for a period of hundreds of years.”

It is interesting to note in this context that Clovis technology has only been found in the New World, whereas Western Stemmed technology is similar to stone technology seen in northeastern Asia.

At least three other Western sites, including Cooper’s Ferry in Idaho, Smith Creek Cave in Nevada, and Bonneville Estates Rockshelter, also in Nevada, also contain only Western Stemmed points in deposits of this early time period.

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Displayed in the hand of University of Oregon archaeologist Dennis Jenkins are three bases for Western Stemmed projectiles from the Paisley Caves in Oregon. The bases date to some 13,000 years ago. [Photo by Jim Barlow]

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Enter here another site, located in Manis, Washington, where the fossil remains of a mastodon were excavated by Dr. Carl Gustafson and a team from Washington State University in the 1970’s. He concluded from radiocarbon dating of charcoal deposits around the remains that it was about 14,000 years old. It was a conclusion that had been the subject of considerable debate among scholarly critics, particularly as he maintained that a bone point found embedded in the rib bone of the mastodon was an early projectile point, similar to other bone projectile points found at other Paleoindian sites.

The case was revisited recently when Dr. Michael Waters of Texas A & M University, the excavator of the Firiedkin site who, along with a team of colleagues, used mass spectrometry to date carbon in samples of bone from the rib, a pair of tusks found at the same site, and the embedded point.  Results indicated that all of the fossils tested were about 13,800 years old. They also used high-resolution X-ray CT scanning of the embedded bone point to produce a three-dimensional visual study or image. Based on this, they determined that the point was likely at least 27 centimeters long, similar in length to those of later, Clovis-age projectile points that were used in throwing or thrusting weapons made by Paleolithic hunters of North America. Moreover, the team examined the specimen using DNA protein analysis of material from the bone point and the rib in which it was embedded. They concluded that the point itself was fashioned from mastodon bone.

Most significantly, the findings constitute more evidence that Paleoindians settled the Americas before 13,000 – 13,500 B.P.E., the earliest date range that has traditionally been assigned to the emergence of the “Clovis” cultural horizon.

Said Waters, “We’re looking at another pre-Clovis locality in North America where, in this case, bone weaponry was used to hunt mastodons 800 years before Clovis stone weaponry show up on the landscape.”

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This is a mastodon skeleton and outline of a mastodon. The location of the rib and approximate angle of the spear is indicated. The point had to penetrate 25-30 cm of hide, tissue, and muscle. Image courtesy of Center for the Study of the First Americans, Texas A&M University 

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Mastodon rib with the embedded bone projectile point. (A) Closeup view. (B) Reconstruction showing the bone point with the broken tip. The thin layer represents the exterior of the rib. (C) CT x-ray showing the long shaft of the point from the exterior to the interior of the rib. (D) The entire rib fragment with the embedded bone projectile point. Image courtesy of Science/AAAS

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But the archaeological finds are not the only body of evidence emerging in the changing picture related to who, when, and from where the first peopling of the Americas took place. New findings are developing with the application of genetic and paleoclimate studies….

Following the DNA Trail

In a study published in the American Journal of Human Genetics, Theodore Schurr, an associate professor in the University of Pennsylvania’s Department of Anthropology, in collaboration with a research team that included Ludmila Osipova of the Institute of Cytology and Genetics in Novosibirsk, Russia and others, analyzed the genetics of individuals living in Russia’s Altai Republic for markers in both mitochondrial DNA and Y chromosome DNA. Mitochondrial DNA traces the maternal, or female line of descent, whereas Y chromosome DNA traces the paternal, or male, descent. They compared the samples to those that had previously been collected from individuals in southern Siberia, East Asia, Central Asia, Mongolia, and a number of different Native American groups.

After analyzing the Y chromosome DNA, the researchers found a unique mutation common to both the Native Americans and southern Altaians in a lineage dubbed as “Q”.  The Altai region is located at the four corners of what is today China, Russia, Mongolia, and Kazakhstan. Says Schurr, it “is a key area because it’s a place that people have been coming and going for thousands and thousands of years. Our goal in working in this area was to better define what those founding lineages or sister lineages are to Native American populations.”  

They found similar results when analyzing the mitochondrial DNA.  “We find forms of haplogroups C and D in southern Altaians and D in northern Altaians that look like some of the founder types that arose in North America, although the northern Altaians appeared more distantly related to Native Americans” says Schurr. 

Determining how long ago the mutations took place, the researchers concluded that the southern Altaian lineage diverged genetically from the Native American lineage about 13,000 to 14,000 years ago. This correlates with current theories that support the migration of peoples into the Americas from Siberia between roughly 15,000 and 20,000 years ago.

The large and diverse nature of the database ensured a relatively high degree of confidence among the researchers about the validity and precision of the findings. Says Schurr, “at this level of resolution we can see the connections more clearly”.

Moreover, the completed research at the Paisley caves has also confirmed, through additional DNA testing, that the early occupants of the caves had ancestral Siberia-East Asian origins, and that they were using the caves as far back as at least 12,450 radiocarbon years ago (about 13,500 calendar years ago). 

The results of another study (published in the July 11, 2012 issue of the journal Nature), while supporting Schurr’s analysis and conclusions, paints a dramatically more complex picture of early American origins.

Led by Professor Andres Ruiz-Linares from the University College London (UCL) and Professor David Reich of the Harvard Medical School, an international team of researchers analyzed data samples from 52 Native American and 17 Siberian groups, examining more than 300,000 DNA sequences to examine patterns of genetic similarities and differences between the population groups. The study was complicated by the fact that the Americas experienced an influx of European and African immigrants since 1492, with 500 years of genetic mixing. To address this, the researchers developed a methodology to isolate genomes that were of entirely Native American origin. “We developed a method to peel back this mixture to learn about the relationships among Native Americans before Europeans and Africans arrived,” Reich said, “allowing us to study the history of many more Native American populations than we could have done otherwise.”

What they found was eye-opening.

“For years it has been contentious whether the settlement of the Americas occurred by means of a single or multiple migrations from Siberia,” said Ruiz-Linares.  “But our research settles this debate: Native Americans do not stem from a single migration”. 

Their results showed that Native American populations originally arose, not from one single migration of people, but at least three. The majority descended from a single original group of First American migrants, but at least two subsequent migrations also made important genetic contributions. Moreover, their origins could be genetically traced to populations traversing across the ancient Beringia land bridge (pictured above, right) that existed during the ice ages over 15,000 years ago. The second and third migrations left their imprint only in Arctic populations that speak Eskimo-Aleut languages and in the Canadian Chipewyan who speak a Na-Dene language. But even these people inherited most of their genetic makeup from the first migration. Eskimo-Aleut speakers, for example, derive more than 50% of their DNA from the first migrants, and the Chipewyan even more, about 90%. This suggests that the two later migrant groups mixed with descendants of the first migrants after they arrived in North America.

Said co-author Reich, “the Asian lineage leading to First Americans is the most anciently diverged, whereas the Asian lineages [the second and third migrations] that contributed some of the DNA to Eskimo–Aleut speakers and the Na-Dene-speaking Chipewyan from Canada are more closely related to present-day East Asian populations.”

What is more, said Ruiz-Linares, “our study also begins to cast light on patterns of human dispersal within the Americas”.

They found that people expanded southward along a route that hugged the coast. As they went southward, population groups split off along the way. After the splitting, there was little gene flow among Native American groups, especially in South America.

But the dynamics were not always this simple. They found, for example, that the first, Central American Chibchan-speakers have ancestry from both North and South America, suggesting a back-migration from South America, and that the Naukan and coastal Chukchi from north-eastern Siberia carry ‘First American’ DNA: the Eskimo-Aleut speakers migrated back to Asia, bringing with them the Native American genetic material.

Clues from a Past Climate

The broadly accepted view about when and how the first Americans entered the Americas has revolved in part around the changes in the glacial periods associated with the last glacial period of the Ice Age. Since about 40,000 B.P., the Cordilleran and Laurentide ice sheets covered much of Canada. However, during the warmer interglacial periods they retreated to create ice-free corridors along the Pacific coast and areas east of the Rocky Mountains of Canada. Scientists have long suggested that it was through these corridors that humans were likely able to cross Beringia into the Americas. Beringia was a land bridge as much as 1,000 miles wide that joined present-day Alaska and eastern Siberia at various times 110,000 to 10,000 years ago. Exactly when and how this crossing may have occurred has been a matter of debate for decades, but the most widely accepted proposal advances the suggestion that it occurred around 15,000 years ago.

A study published in the professional journal, Quaternary Science Reviews, resulted in findings that differ from this prevailing hypothesis by as much as 2,000 years. Led by Nicole Misarti of Oregon State University, the study, known as the Sanak Island Biocomplexity Project and funded by the National Science Foundation, was intended to examine the abundance of ancient salmon runs in the Beringia region. They analyzed core samples taken from Sanak Island, a remote island about 700 miles from Anchorage, Alaska, and about 40 miles from the coast of the western Alaska Peninsula. As the researchers began examining core samples from Sanak Island lakes looking for evidence of salmon remains, they came up with radiocarbon dates much earlier than they had expected. The dates were based on organic material in the sediments, composed of terrestrial plant macrofossils that indicated the region was actually ice-free earlier than believed. Deglaciation there from the last Ice Age, it seemed, took place as much as 1,500 to 2,000 years earlier. Moreover, the researchers had also concluded that the maximum thickness of the ice sheet in the Sanak Island region during the last glacial maximum was actually only 70 meters – or about half that previously projected.  This suggested that deglaciation could have happened more rapidly than earlier models had predicted. Given the location, this opened the door for the possibility of earlier coastal migration models for the Americas.

“It is important to note that we did not find any archaeological evidence documenting earlier entrance into the continent,” said Misarti. “But we did collect cores from widespread places on the island and determined the lake’s age of origin based on 22 radiocarbon dates that clearly document that the retreat of the Alaska Peninsula Glacier Complex was earlier than previously thought. Glaciers would have retreated sufficiently so as to not hinder the movement of humans along the southern edge of the Bering land bridge as early as almost 17,000 years ago.” 

This shed new light on a long-standing question. If humans had not arrived in the Americas until about 15,000 B.P. as traditional models had suggested, then how could they have spread so quickly to inhabit areas thousands of miles southward, as evidenced archaeologically by their presence at sites such as Monte Verde, Chile, and Huaca Prieta, showing remains dating back to 14,000 to 14,200 years ago? The answer, based on the Sanak Island findings, was that they had actually arrived in the Americas up to 2,000 years earlier.

Another finding was related to the presence of pollen in the samples.

“We found a full contingent of pollen that indicated dry tundra vegetation by 16,300 years ago,” Misarti said. “That would have been a viable landscape for people to survive on, or move through. It wasn’t just bare ice and rock.”

Moreover, she added, based on the findings in the tested area, “the region wasn’t one big glacial complex. The ice was thinner and the glaciers retreated earlier.” Furthermore, previous studies have indicated warmer sea surface temperatures possibly preceding the retreat of the Alaska Peninsula Glacier Complex (APGC), creating conditions more favorable to supporting productive coastal ecosystems that humans could have exploited.

Thus, if the researchers are right, the stage for human entry into the Americas had been set earlier than long theorized. As they wrote in the published study: “While not proving that first Americans migrated along this corridor, these latest data from Sanak Island show that human migration across this portion of the coastal landscape was unimpeded by the APGC after 17 (thousand years before present), with a viable terrestrial landscape in place by 16.3 (thousand years before present), well before the earliest accepted sites in the Americas were inhabited.”

The Emerging Picture

Taken together, new discoveries and research results are thus beginning to paint a picture of a human beginning in the Americas that is considerably more complex and likely earlier than previously thought.

That genetic studies have shown that a single original population of modern humans dispersed from southern Siberia toward the Bering Land Bridge, or ancient Beringia, as early as about 30,000 years ago, and further dispersed from Beringia to the Americas by perhaps 16,500 years ago. But there was more than one migration event, and some of them traversed from the Americas back into Asia. From the paleoclimate evidence, we see indications that the environmental stage was set by at least 16,300 years ago for an accommodating passage for humans into the Americas. From archaeology, we know that humans appeared south of the Canadian ice sheets by at least 15,000 years ago, 2,000 or more years before the emergence and spread of the Clovis culture, and it is no longer clear that there is a clear linear evolutionary relationship between the Clovis culture and early technology discovered in the western regions of the North American continent.  Finally, from archaeology, evidence builds to support a suggested route along the deglaciated north Pacific coastline.

To be sure, new discoveries could significantly change or challenge this developing paradigm of the peopling of the American continents, but it could also continue to strengthen it. Time and continuing research will tell. Writes a researcher at the Center of the Study for First Americans at Texas A& M University: “This is an exciting time to be studying the peopling of the Americas. We are confident that through continued empirical research and active interdisciplinary dialog, we will soon know precisely when and how humans dispersed across the New World.”[1]

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[1] The Story of the First Americans, The Center for the Study of the First Americans.  http://csfa.tamu.edu/who.php

Article cover image, top left: Excavation team at work at the Friedkin site in 2016. Courtesy Michael R. Waters and Center for the Study of the First Americans, Texas A&M University

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Meadowcroft

By Dan McLerran

Peering up at it from below, I could see that this wouldn’t be a leisurely stroll. This flight of seemingly countless steps, ascending with rails almost like scaffolding to a destination high above, invited a small sense of adventure. But I could envision that, long before this modern, convenient construction, human visitors surely had a more challenging task. I was told that casual visitors once had to ascend with the aid of a rope assemblage, and long before that, Native Americans had to reach it using whatever devices or efforts at their disposal. Carved by nature in a bluff overlooking a tributary of the Ohio River known as Cross Creek, the ancient rockshelter above had remained tucked away for millennia within a lush green, hilly landscape of what is today called the Allegheny Plateau of western Pennsylvania. Thousands of years of weathering and erosion made this place a cave-like shelter for prehistoric human sojourners—affording them protection from the elements without and a space to rest, sleep and eat within.

Once I reached the top of the steps, I could move freely over a spacious, human-made platform, designed to hold small capacity crowds. I could now see the interior of the rockshelter clearly laid out before me, left as it was after the latest archaeological excavations closed out (although the site continues to be investigated). But long before archaeologists and others came to investigate and work at the site, nature’s hand had already morphed its appearance many times over through thousands of years of weathering and erosion. I could see the visible reminders of this in the face of the sandstone cliffs surrounding it. Slowly sculpted by water, wind and ice, it was an almost surrealistic picture of what time and the elements could do to otherwise seemingly impermeable and impenetrable stone. Today, the rockshelter is enveloped in an impressive, protective overhanging wooden construction, an architectural wonder by itself.

Archaeologists, historians and the public call this place Meadowcroft. For those who know something about the site, the Meadowcroft rockshelter is now widely thought to have yielded evidence of the earliest known presence of humans in North America, along with the longest sequence of continuous human occupation. It was first systematically excavated by Dr. James M. Adovasio.  His efforts included a team of colleagues and field school students in the early 1970’s. All together, they uncovered evidence of a human presence they suggested dated thousands of years before the time of the advent of the first broadly recognized human culture in the Americas—the Clovis—and its implied first peopling of the North American continent. Their dating at this site pushed the clock back on human occupation of North America to as much as at least 16,000 years ago. 

But this stature and acceptance didn’t come quickly and easily for Meadowcroft and its chief archaeologist. It challenged the prevailing paradigm, radically pushing back the dates on human occupation of the continent. From the very beginning, the validity of his findings related to the earliest human modified stone objects and other features of human habitation found at the site were marked with controversy. Decades later, however, the story of the Meadowcroft controversy has evolved to one of broad acceptance. Partly due to the mounting evidence from other sites with Pre-Clovis artifacts across the Americas, and in no small measure to the meticulous and scientifically rigorous methods used in the Meadowcroft research, the site has arguably become a kingpin in a new mainstream of scientific inquiry that has increasingly legitimized the ‘Pre-Clovis’ way of thinking. Today, Meadowcroft is designated as a National Historic Landmark, drawing thousands of visitors yearly.   

Popular Archaeology took the opportunity to interview Dr. Adovasio (pictured below, right) about the site and its significance within the context of the ongoing search and debate on the first peopling of the Americas. What follows are the details of that interview: 

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 Q1: Would you describe your personal route/experience, attributes and interests that drove you to your current occupation or career? 

As I indicated in my book, “The First Americans,” I was essentially programmed to be an archaeologist by my mother, Lena M. Adovasio. She was a four-field major in college, one of which was history and another of which was chemistry. She taught me to read well before kindergarten with geology, paleontology, and archaeology books. As a consequence I never really wanted to do anything else except pursue an archaeology career. I knew where I wanted to go to undergraduate school in the 6^th grade and, in fact, attended that institution (The University of Arizona). The attributes which I brought to the “archaeology table” were and remain, extreme attention to detail, a high degree of organization leavened with intense self-discipline, and, I suppose, the ability to absorb and synthesize oftentimes very diverse data sets. It probably helped that, like my mother, I was endowed with a near perfect memory.

Q2: What is the story of how Meadowcroft first came to your attention?

When I assumed a faculty position at The University of Pittsburgh in 1972, I was told that one of the parameters of that position was the establishment of an archaeological and geoaracheological field training program in western Pennsylvania. What I had hoped to locate was an area with little or no previous archaeological or geoarchaeological research coupled with relatively easy striking distance of Pittsburgh for obvious logistical reasons. I also sought an area which contained at least one cave or rockshelter site because these were the sites I was most familiar with from my graduate career at The University of Utah. Because I had previous research commitments on the Island of Cyprus in the eastern Mediterranean, I did not have the time to locate a suitable study area myself. So I circulated word amongst my colleagues in the profession, and as a result, a now deceased historian/amateur archaeologist from what was then California State College, California, Pennsylvania, informed me about Meadowcroft Rcokshelter in the early spring of 1973. His name was Phil Jack, a longtime friend of the landowner, Albert Miller, who discovered the site. I arranged with both of them to visit the site in the later spring of 1973 and upon viewing it decided to solicit permission from the landowners to begin excavations there in June of 1973. The rest is, literally, history.

Q3: While excavating at Meadowcroft in the 1970’s, what was it that made you realize that there was something special or unusual about this site?

We initially believed that the deposits at Meadowcroft would be something less than a meter in thickness and that the oldest occupation would be Late Archaic or Early Woodland, at best. These estimates were based on excavations at other rockshelters in southwestern Pennsylvania and adjacent portions of Ohio and West Virginia. However, early in the 1973 season it became clear that the deposits at the site were well in excess of a meter in thickness and the recovery of Middle and Early Archaic materials signaled an older occupation than we had imagined. Of course, when the first radiocarbon dates were run after the 1973 season was over, it was evident that the site was initially occupied earlier than we suspected.

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General view of Meadowcroft Rockshelter facing west before excavation in 1973; vegetation marks the limits of the vegetation current overhang; large block in lower left represents a roof detachment ca. 12,500 years ago. Image courtesy James  M. Adovasio

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Q4: What finds convinced you that you had uncovered evidence of human occupation at this site going back possibly 16,000 years or more?

The answer to this question is more complicated than it seems. The deposits at Meadowcroft are characterized by a series of roof spalling and block collapse events which dramatically altered both the configuration of the rockshelter, as well as the availability of “livable” floor space through time. One such spalling event marks, in effect, the Pleistocene-Holocene boundary as well as, for all intents and purposes, the end of the Clovis interval in southwestern Pennsylvania. Beneath this spalling event, we expected to encounter no additional, older cultural material, but rather the parent bedrock of the rockshelter in the form of the Birmingham Shale. Instead of the Birmingham Shale, we found a series of apparent occupational surfaces replete with shallow fire pits and associated artifacts of indisputable anthropogenic origin. Radiocarbon dates derived from charcoal within these pits clearly preceded the established age of Clovis in eastern North America, thereby, and surprisingly to us, indicating an earlier than Clovis occupation. Additionally, none of the recovered artifacts, most notably the unfluted lanceolate so-called Miller projectile point [named after the site’s discoverer] and small blade flakes, were consistent with a Clovis ascription.

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Lithic shown under rockfall is the type specimen of the Miller Lanceolate projectile point form. Courtesy James M. Adovasio

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Miller Lanceolate projectile point type specimen, obverse surface; the specimen is significantly re-sharpened and reduced in overall dimensions from the hypothesized prototype; it is unfluted, but basically ground. Courtesy James M. Adovasio

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Assorted Miller Complex artifacts from Stratum IIa (containing the oldest cultural remains radiocarbon dated to about 16,000 years B.P.) at Meadowcroft Rockshelter; from left to right: Miller Lanceolate type specimen made of local Cross Creek chert, prismatic blade flake made from Onandaga chert, prismatic blade flake made from Flint Ridge chert, biface fragments made from Flint Ridge or Kanawha chert (black specimens are Kanawha). Courtesy James M. Adovasio

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Q5: What is the significance of these findings within the context of the Clovis First debate?

Meadowcroft was the first site in nearly 40 years to seriously challenge the long held Clovis-First paradigm. Between 1933 and 1973, more than 500 archaeological sites in North and South America were claimed to be older than the Clovis horizon of ca. 10,900 to 11,300 uncorrected radiocarbon years ago. Prior to Meadowcroft, all of these Pre-Clovis claimants exhibited a similar history. First, you would read about them in a local newspaper or popular scientific journal, then more extensive treatments would appear in the technical scientific literature. Inevitably, the sites would then be exposed for some real or imagined flaw – the artifacts were not definitively of human origin; the stratigraphy was non-existent or imperfectly defined; the context and association of even genuine recovered artifactual material was problematic, etc. As I pointed out in “The First Americans,” each of these sites enjoyed a Warholesque 15 minutes of fame, then disappeared into oblivion. Each time one of these claimant sites failed, it reinforced the Clovis-First model. Therefore, by the time the initial reports on Meadowcroft appeared, there was a long established record of failure which served to render the Meadowcroft discoveries suspect ab initio.

Q6: Do you think the Clovis First paradigm is now discredited, or on its way out, given the findings from other sites across the Americas that show evidence of human occupation before Clovis times? (In other words, do you think there is sufficient evidence now to support a pre-Clovis presence or culture in the Americas, and why?)

To answer this question, it is perhaps useful to cite an observation by Dr. Jonathan C. Lothrop in his review of a Pre-Clovis site in the Americas, a  volume published by the Smithsonian Institution. He says,

“In 2015, if one polled New World archaeologists familiar with the literature, I suspect most would agree that there is a growing body of evidence of human occupation in the Americas that pre-dates ca. 13,200 Cal. B.P.” (Lothrop 2015: p. 256)

I certainly concur with Lothrop’s assessment, but it is also worth stressing that a handful of very vocal, Clovis-Firsters still remain and, like Hrdlicka in an earlier time, will probably go to their graves with their minds unchanged. The death of established paradigms often takes a very long time—as witnessed, for example, by the many decades which elapsed between the promulgation of continental drift and its widespread acceptance in the geological community. I completely underestimated how long it would take for Clovis-First to expire and I also misjudged the degree to which its “spear carriers” would hold on to their beliefs. This is all particularly interesting given the fact that, almost from its inception, most European scholars and virtually all South American scholars questioned the underpinnings of the Clovis-First model. The American response, of course, was that the Europeans were simply ignorant of the facts and that the South Americans didn’t even publish in English. The number and distribution of what might be called broadly acceptable Pre-Clovis archaeological sites now clearly points to an earlier than Clovis presence. I stress, however, that even if there were only one, then one would be sufficient. Monte Verde effectively terminated the argument even if its still vocal critics don’t accept the fact.

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Blade flakes from Stratum IIa at Meadowcroft Rockshelter; cross sections range from prismatic on the first three specimens to triangular on the forth; the edge is intentionally dulled for hafting. Courtesy Jame M. Adovasio

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Bifaces from Stratum IIa at Meadowcroft Rockshelter. Courtesy James M. Adovasio

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Close up of blade flakes from Meadowcroft Rockshelter; one edge of each blade flake is intentionally dulled for hafting, while the opposite edge is the working edge. Courtesy James M. Adovasio

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Polyhedral blade cores of the type from which Meadowcroft blade flakes were struck; these are very different from Clovis blade cores. Courtesy James M. Adovasio

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Fractured punch made of antler and truncated blade flake lying upon a 13,500 year old surface. Courtesy James M. Adovasio

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Q7: What were the specific challenges of excavating and investigating the site?

All cave and rockshelter sites around the world are part of what some archaeologists call the “marked landscape”. Places so designated were well known to aboriginal populations both in time and through time and as such, were frequently visited and utilized. While some of these sites probably witnessed yearly visits, many were only episodically visited. Because of repetitive visits, often over very long periods of time, such sites provide the opportunity for studying environmental change and concomitant human adjustments to those changes in very unique ways. Unfortunately, depending on the nature, intensity, and duration of these visits, these types of sites may evidence considerable anthropogenic disturbance with attendant difficulties in establishing the stratigraphic/occupational sequence. Additionally, because of the nature of the depositional process in many of these sites, even without human disturbance, the stratification may be remarkably complex. The combination of naturally complicated stratigraphy and repetitive human visits with attendant disturbance render the proper excavation of these kinds of sites very difficult.

Q8: What specific techniques, processes, methodologies and applications made the investigation of this site stand out from other excavations or investigations?

A necessary preamble to this answer is to state that a field archaeologist in virtually any setting – prehistoric, historic, or forensic – has three basic responsibilities. The first, and most fundamental of these, is the reconstruction of stratigraphy from visible stratification. While in English, we tend to use the terms “stratigraphy’ and “stratification” interchangeably, they do not, in fact, mean the same thing. Stratification is an objective phenomenon. It has both subjective and objective physical properties which can be detected, assessed, and measured. Stratification is a product. Stratigraphy is both the process by which stratification is created and the study of that process. The establishment of stratigraphy from observable stratification is fundamental and critical to the other two responsibilities of a field archaeologist. Without it, the other two cannot be done. The second responsibility is the delineation of context. Context literally means place in time and space and unless the context of all recovered material is explicitly defined in a stratigraphic perspective, there is no context. Finally, perhaps the most difficult field responsibility is the demonstration of association. Association means that two or more items have entered the archaeological record penecontemporaneously as a consequence of the same process. Association refers, in forensic terms, to primary or probative evidence as opposed to secondary or circumstantial evidence.

Suffice to note, for reasons already articulated, it is particularly and peculiarly difficult to execute the three responsibilities of a field archaeologist in a cave or rockshelter situation. To execute these responsibilities in any excavation situation requires knowledge of and the ability to operationalize all of the so-called laws of stratigraphy. While most people are familiar with the first of these laws – superposition – many are, to varying degrees, unfamiliar with the remainder. These include original horizontality, lateral continuity, and intersecting relationships. The key to operationalizing all of these principles – frequently referred to as Steno’s Laws – requires the ability to recognize and delineate the contacts or interfaces between discrete strata. Without digressing into an arcane lecture on methodology, it should be noted that during the Meadowcroft excavations much of our attention was directed precisely at facilitating and defining interfaces and contacts. Students were exhaustively trained to recognize strata differences on the basis of perceived textural differences. In practice, this meant that they could use their trowels to detect differences in compactness versus friability, density versus porosity, and related properties by feel and even sound. Once sufficiently skilled, our students could recognize stratigraphic differences quite literally with their eyes shut in much the same way that anyone could detect by feel and sound alone the difference between layers of cake and icing between those layers. Despite the reliance on texture in the excavation training process, a wide array of other things were done to maximize the ability to “see” stratigraphic transformations in profile. Meadowcroft, virtually from the outset, was fully electrified and thanks to University of Pittsburgh engineers in conjunction with assistance from Westinghouse, we were able to install an experimental lighting system that allowed the excavators to combine different light sources to illuminate stratigraphic profiles in a variety of ways. The difference between different light source combinations was and is striking and, at that time, had not been employed extensively as a supplement to excavation.

In order to systematically plot the three-dimensional Cartesian coordinates of artifacts and ecofacts, a series of vertical and horizontal datum points were combined, initially manually, and later, via total stations, to ensure the establishment of the appropriate provenience or context of excavated materials. Since the rockshelter had an active phone line, we could then communicate directly via telephone modem to the mainframe at the University of Pittsburgh to encode excavation data. To my knowledge, this is also the first time that was ever done – at least in a cave or rockshelter setting.

In order to provide objective verification of what were subjectively defined strata, samples of sediment from each stratum or microstratum were processed with a Coulter blood cell counter converted to measure sediment size differences. Once again, this was the first time such technology had been employed in the field.

I could continue in this vein, but the point here is simply this – given the experience and imagination of the investigators, coupled with sufficient funding, we were able to implement a variety of data recovery and documentation as well as analytical protocols which had never been extensively employed before. While some of these did not work as expected, many did. The collective effect was a level of precision in the excavations which virtually no critic of the site has ever questioned.

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Precision and care: Excavation of a thin anthropogenic surface at the site via single-edged razorblade. Courtesy James M. Adovasio

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Above and below: On-site documentation procedures at Meadowcroft Rockshelter; colored pencils which represented different combinations of silt, sand, and clay-sized materials were employed to produce microstratigraphic profile maps of all parts of the excavation. Courtesy James M. Adovasio

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Q9: What arguments or issues did you have to address regarding the validity of the finds and their dating?

Virtually from the publication of the first radiocarbon chronology from Meadowcroft in 1974, the possible age of the earliest occupation of the site engendered great controversy. Significantly, especially as compared to other putative Pre-Clovis claimant localities, none of this controversy surrounded either the excavation methodology employed at the site nor the possible anthropogenic origin of any of the earliest artifacts. As already noted, the excavations at Meadowcroft were, and still are, widely hailed as “meticulous” and the “early” artifacts bear the unmistakable stigmata of humanly modified materials. Instead, the criticisms of the possible antiquity of the site pivoted around three basic issues: 1) the possible particulate or non-particulate contamination of only the eleven oldest radiocarbon samples from the site; 2) the absence of Pleistocene faunal remains; and 3) the apparently anomalous character of the recovered floral materials.

Dozens of pages of published material have been devoted to refuting the objections to the apparent age of the lower and middle Stratum IIa materials from Meadowcroft and these arguments will not be repeated here. It should be sufficient to note that there is absolutely no probative evidence for the particulate contamination of any of the eleven oldest C-14 samples from Meadowcroft. As to non-particulate contamination, the introduction of dissolved older carbon into just the eleven deepest radiocarbon samples from Meadowcroft requires a vehicle for contamination in the form of groundwater movement. An intensive micromorphological study conclusively demonstrated that such movement did not occur and, therefore, the non-particulate contamination issue is moot.

As to the faunal and floral critiques, modern research indicates that the paleoenvironment south of the glacial ice front in North America was remarkably variable and diverse. Further, the floral species represented at Meadowcroft were not inconsistent with such diversity. Finally, the faunal remains from Meadowcroft’s oldest deposits are diminutive both in numbers and weight, though all of the species represented have been reported in Late Pleistocene contexts elsewhere in eastern North America.

Put most simply, all of the currently available data suggests that Meadowcroft was sequentially and sporadically visited before the advent and spread of Clovis technology by populations who may or may not have been the ancestors to the makers of fluted points.

Of course, a larger issue, at least for some scholars, was the absence for a period of time of “other Meadowcrofts.” Now, of course, there are other sites of demonstrable Pre-Clovis age. Despite the best efforts of diehard Clovis-Firsters to discredit these other localities, often with incredibly convoluted and far-fetched scenarios, the existence of Pre-Clovis populations in the new world is now widely accepted.

Meadowcroft set the evidentiary bar! Monte Verde broke it! Other sites are appearing to join them. For Clovis-First it is the end of the game.

Q10: If you were to create a scenario or story describing the nature and lifestyle of the early, Pre-Clovis inhabitants of the site, what would it be?

As described in various publications, the earliest visitors to Meadowcroft appear to have been broad spectrum foragers rather than megafauna-focused big game hunters. These populations visited the site, as would their successors, principally in the fall of the year, utilizing a durable technology that included the production of unfluted lanceolate projectile points and the manufacture of diminutive blade flakes from polyhedral cores. They also employed a perishable technology that included basketry and presumably a variety of other less well documented related technologies. Their visits to Meadowcroft were apparently brief and perhaps separated by a number of years. They exploited a wide array of lithic raw material sources which I personally do not believe reflect their range. I would suspect these materials were acquired by trade and exchange. These sources include Kanawha chert from West Virginia, Onandaga chert from New York, and Flint Ridge chert from Ohio to name but a few. Evidence of these earliest visitors to Meadowcroft, named by us the Miller Complex after Albert Miller who discovered the site, are also evidenced at several other localities in the Cross Creek Drainage and a very similar durable technology is also evident at more remote locations like Cactus Hill in Virginia. While there are no obvious technological connections between Miller durable technology and Clovis, there is the possibility that some sort of relationship may be discovered in the future.

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Reenactment of Paleoindian family unit showing both genders, different ages, durable and non-durable technology. Courtesy James M. Adovasio

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Q11: What is in store for the future investigation and research of this site?

About one third of Meadowcroft remains unexcavated. This area is available for future study when there are even more resolute excavation, documentation, and analysis protocols available. The main task at present is to complete the long overdue final report as well as a series of smaller contributions about one or another aspect of the long Meadowcroft sequence.

Q12: Are there any other comments you would like to make?

The Meadowcroft/Cross Creek operation was originally designed as an undergraduate and graduate training project aimed at both anthropology/archaeology students and those in related fields. Obviously, there was also a research component but this was, at least on paper, secondary to the student training goal. Because of the experience of the multidisciplinary research staff as well as access to extraordinary funding, it was possible to not only offer students state-of-the-art protocols in site excavation, documentation, and analysis, but also to constantly refine those protocols from both a methodological and substantive perspective. Because of the foregoing, the excavations at Meadowcroft were considered by others to be at the very cutting edge of the field. That they are still considered by many to be so is a testimony to the success of the methodological aspect of the project. We have always been more proud and pleased with the methodological “end” of the Meadowcroft project than any, or even all, of the results it produced. Expanding the envelope of the field in any perspective is rewarding, but in terms of actual enhancement of field data collecting procedures, it is and has been particularly gratifying. From a more substantive perspective, while the earliest materials from Meadocroft have garnered the most attention, the incredible length of the occupational sequence is to us far more striking. Because of the lengthy and hyper-detailed Paleo-environmental record from Meadowcroft, we can examine macro and micro climatic changes and their attendant consequences very precisely. We can also articulate in unique ways human responses and adjustments to those changes. That was in essence the “cake” we were trying to bake. That the site proved to be quite old was the unintended “icing.”

For more information about the Meadowcroft Rockshelter and other related attractions at the site, see the website, Meadowcroft Rockshelter and Historic Village.

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The Pre-Clovis Site of Page-Ladson

By Michael Gordon

Underwater excavations at the 14,600-year-old Page-Ladson site. Center for the Study of the First Americans, Texas A&M University

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As it traverses the marshy Gulf coast lowlands of the Florida panhandle’s Big Bend region, the aquifer-fed Aucilla River would not fit the typical description of a North American river. It flows visibly above the surface in places, like most rivers do, but then disappears in other places into an ancient underground sinkhole system, carved into a vast limestone bedrock foundation over time by geological processes of erosion and collapse. Many thousands of years ago, one might not have recognized it as a river at all. Back then, when sea level was much lower, it was simply a series of sinkholes of various sizes, clearly visible from the surface. Today, the river is an underwater treasure trove of fossilized remains of long-extinct creatures. Needless to say, it has been an important paleontological destination for scientists conducting research on the North American Pleistocene past. 

One place along the river, known as the Page-Ladson site, has recently yielded some tantalizing finds — evidence of a very ancient human presence, people who lived here before the Clovis era more than 14,000 years ago.

But few people can actually see this site. It lies submerged under about 30 feet of water and additional layers of sediment within a bedrock limestone sinkhole 60 meters in diameter. It is the exclusive domain of scuba divers. Everyone else, at the surface, only sees the slow-moving river flowing through a thick cypress swampland. During Pleistocene times, however, this sinkhole was essentially dry and easily accessible, and for the animals of the time, it had a particularly attractive feature — a small freshwater pond at its base. We know this because, since the mid-1980’s, scientists have studied the geology and recovered bones and other evidence there that tell a story of giant Ice Age mammals frequenting the pond for its fresh water.

Digging Page-Ladson

It was in the early 1980’s when Buddy Page, a recreational diver and avocational archaeologist, recovered elephant bones beneath the surface of what is today known as the Half-Mile Run section of the Aucilla River. Thinking that any further investigation would require the services of a professional team of scientists, he reported the site and his finds to Jim Dunbar, then of the Florida Bureau of Archaeological Research, and David Webb, professor of Vertebrate Paleontology at the University of Florida. Together with a team of divers and other experts, Dunbar and Webb proceeded to excavate and study the site beginning in 1983, discovering in the process eight stone artifacts, mostly flakes, in association with butchered mastodon bones within a deposit dated through radiocarbon dating techniques to more than 14,400 years old. Most remarkable was an adult mastodon tusk that exhibited what appeared to be human-made cut-marks. 

The findings were not without controversy. The age of the finds based on the dated deposit “was an impossible age for the scientific community to accept at the time,” says Jessi Halligan of Florida State University, a co-author of the most recent study and report on the Page-Ladson site, “because it was well-accepted that the Americas were colonized by the Clovis people who arrived on the continent over the Bering Land Bridge no more than 13,500 years ago at the oldest.”

Part of the difficulty surrounded the nature and difficulty of the location. “As an underwater site, it could not be visited by just any member of the archaeological community, so the discoveries could not be verified by impartial peers,” says Halligan. “And everyone knows that rivers are destructive earth-movers, so it seemed quite possible that even if the layers were as old as the researchers reported, that the material may not be cultural at all.” 

Dunbar and Webb published their research on the findings, but for years their findings, enshrouded in dispute, were consigned to near oblivion.

Until 2012.

Texas A&M University’s Center for the Study of the First Americans decided to take on the challenge by returning to Page-Ladson to finally resolve the status of the site. “I always thought the site had great potential to help us resolve the issue of whether people were here before Clovis and I always wanted to investigate the site,” said archaeologist Michael Waters, Director of the Center.  “I got my chance in 2012 when John Ladson [the owner of the property surrounding the site] invited me to investigate the site.” 

Waters, long a well-known name in First American studies, turned to Jessi Halligan to join him as co-director of the new project. Halligan, a veteran of 20 years in North American archaeology and who studied under Waters at Texas A&M, had already been deeply involved in Aucilla River research since 2007. Together, they headed a group composed of scientists and divers that would lend the best expertise to the total research effort. It was a perfect team.

But the challenges were considerable. First of all, the site was 30 feet underwater, requiring SCUBA access. Communications between divers during any excavation thus meant using hand signals and notes written on mylar clipboards. Because the river water was stained into a dark red color by tannins, most sunlight could not penetrate the depths to the site, so lights were needed to work. Safety was a premium, so work demanded extensive logistics which required diving in teams of two, redundant SCUBA equipment, a dredge and dredge operator for the dive teams, and additional divers at the surface to manage the divers and air supply. All materials recovered and brought to the surface had to be meticulously dried and conserved, a time-consuming process. 

Added to this were the environmental and weather conditions. “We were hot, dirty, and bitten by bugs,” said Waters. “The first year we worked at the site, we were plagued by flooding and hurricanes.” 

Reaching their goal of finding new evidence of pre-Clovis occupation proved elusive at first. “The area we excavated yielded no artifacts,” wrote Waters to Popular Archaeology. “We confirmed the stratigraphy and found some bones of extinct animals, but we needed artifacts.”

But for Waters and Halligan, persistence was the name of the game. “We were convinced we needed to give it another try and the next season we had better weather,” said Waters.

Along with the better weather came better results. In 2013, Waters and Halligan hit their  ‘pay dirt’. There were multiple dives, but on one dive, a crew that included Morgan Smith, a graduate student of Waters, and John Albertson, went down to  clean up an excavation unit and began to excavate a new level. As they dug, Albertson’s trowel met some resistance. Fanning the sediments away, he found what appeared to be an artifact — a biface. Leaving it in place, Smith came up to the surface to announce the new discovery. 

“We decided to collect samples from all around the biface and above it and below it for radiocarbon dating so that there would be no confusion about its age,” said Waters. “In the end, 71 samples were radiocarbon dated and confirmed the age of the artifact to 14,550 years ago.”

Finally bringing the artifact up to the surface after the dating samples were taken, they determined upon examination that it was indeed a biface — a reworked knife fragment — lying in the same deposit that contained the remains of extinct mammals — mastodons, camels and bison. This was the same deposit in which Dunbar and Webb had discovered the mastodon tusk that featured cut-marks — the multiple, parallel, deep linear grooves that ran perpendicular to the long axis of the tusk — clear signs of human activity. Other flakes were found within the same or similar deposits, bringing the total artifact finds to six. 

“We were all excited,” Waters wrote Popular Archaeology. “I will never forget that day and the feeling of excitement when the artifact came to the surface. It was like a moment when you know you have found something special that will change a long held paradigm.”

Waters was right. It was a moment, like some other moments at other sites, that would change what we know about when and how the first Americans made their debut in the Americas.

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Surface setup at the site, showing the floating screen decks with yellow hoses leading to divers underwater, bubbles by buoys are air bubbles from divers. Pictured are John Albertson, Rodrigo Torres, and Jessi Halligan on floating screen decks. Photo by Adam Burke. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Halligan waiting to begin a dive. Photo by Brendan Fenerty. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Halligan and Neil Puckett examining find. This is a juvenile mastodon radius. Photo by Brendan Fenerty. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Puckett bringing subadult mastodon bone to surface for conservation. Photo by Brendan Fenerty. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Halligan excavating underwater during 2015 season. Photo by Shawn Joy. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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The pre-Clovis biface in place at the bottom of the 2013 excavation block just after discovery. Photos by Jessi Halligan. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Excavation Schematic Image by Jessi Halligan. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Morgan Smith and Michael R. Waters examining biface immediately after its discovery (by Smith and his dive buddy, John Albertson). Photo by Adam Burke. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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Tusk reassembled. Adult mastodon tusk from ARPP excavations at the Page-Ladson site (UF 150701) shown reassembled for Dr. Daniel Fisher’s reexamination of the cut-marks. Jessi Halligan, Cindy Fisher, and FLMNH researcher Jason Bourque shown. Photo by Daniel Fisher. 

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Making the Case 

“The Gold Standard necessary to demonstrate unequivocally that a site pre-dates Clovis has always been 1) clear evidence of human activity usually in the form of stone tools; 2) artifacts occurring in a solid geologic context, and 3) artifacts dated using a reliable dating technique,” asserts Waters. Page-Ladson, they maintain, meets all of these criteria for several reasons:

1. At Page-Ladson, unequivocal lithic artifacts, including a bifacial knife and utilized flakes, are associated with mastodon remains (including a tusk with stone tool marks).  
2. These artifacts are sealed in undisturbed geological deposits at the base of a 4-m-thick stratified sequence.  
3. Seventy-one new radiocarbon ages show that the artifacts date to 14,550 years ago and that the stratigraphy at the site is undisturbed.* 

Armed with this evidence, Waters and Halligan suggest that the site plays a significant role in informing the ongoing debate about how and when the first peoples of the Americas settled the landscape and what they were doing. They point to the research showing that Page-Ladson is about the same age as the Monte Verde site, indicating that people were living on both American continents at least 14,500 years ago; that there were also people, based on archaeological finds, present at this time in Washington, Oregon, Texas, Wisconsin, and Pennsylvania; that the findings are consistent with the genetic research showing a pre-Clovis presence in the Americas; and that evidence in the form of dung fungus at Page-Ladson indicates that large mammals like mastodons became extinct around 12,600 years ago, showing an overlap of humans and a large extinct mammal presence, suggesting the possibility that human hunting may have had an impact on their extinction. 

Most significantly, the Page-Ladson finds feed into an emerging new paradigm. “At the time people were butchering or scavenging a mastodon carcass at 14,550 years ago at Page-Ladson, the Ice Free Corridor or inland route into the Americas would have been closed,” Waters concludes.  “The evidence from Page-Ladson provides indirect support for a coastal migration into the Americas.  How people made their way to Florida and how long this took, we can only speculate, but this [obviously] hints at an even earlier arrival of people into the Americas.”

Popular Archaeology asked Halligan if she, based on the findings, could reconstruct the scene that existed at this place so long ago in prehistory:

What we have evidence for is the  following: 14,500 years ago, people were within this steep-walled sinkhole butchering a mastodon at the edge (and possibly partially within) a shallow pond. They expended a great deal of effort to extract a tusk that they later left behind, either because they were only interested in the fatty meat within the tusk cavity, or because they wanted to leave it preserved in the shallow pond for later, but never returned for it. The evidence from this site is sparse, but its location and contents can tell us some important things: this site shows people were well-familiar with the landscape, and knew where to get stone for toolmaking, knew how to extract a tusk, and knew when, where, and how to access freshwater. In other words, they were very capable and competent hunter-gatherers who probably were pretty familiar with this landscape. 

Looking Ahead

For now, neither Waters nor Halligan have any immediate plans to return to the field at Page-Ladson. It doesn’t mean, however, that work is over. Project staff is busy documenting the findings from the younger strata at the site, including pollen and spore analysis and special studies on core and sediment samples, and Waters and Halligan are also continuing their search for other sites that may bear on the earliest Americans.

In the end, whether or not scientists return to Page-Ladson for further excavation and survey, the site is already well on its way to leaving a legacy.

“The record of human habitation in the Americas between 14,000 and 15,000 years ago is sparse, but it is real,” concludes Waters. “The few stone tools and the other evidence left behind by hunter-gatherers at the bottom of the Page-Ladson sinkhole 14,550 years ago will have a long lasting and profound impact on our understanding of the earliest pioneers and explorers of the Americas.”  

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Diving crew lined up for survey work. These divers are waiting to conduct a survey, looking for new sites. Photo by Jessi Halligan. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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*Michael Waters, response to Popular Archaeology inquiry, January 2017.

Information for this article was obtained from a variety of sources, including written interviews with Michael Waters and Jessi Halligan, as well as the detailed study report cited below.

Halligan et al., Pre-Clovis occupation 14,550 years ago at the Page-Ladson site, Florida, and the peopling of the Americas,  Science Advances 13 May 2016;2:e1600375

Cover image, top: SCUBA diver Ivy Owens collecting micromorphology samples during 2015 season. Photo by Shawn Joy. Provided courtesy of the Center for the Study of the First Americans (CSFA).

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West Coast Rising: Huaca Prieta

By James Kensington

View of the Huaca Prieta site on the coast of Peru. Courtesy Tom Dillehay

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Just north of the bustling city of Trujillo, a distinctively imposing 30-meter-high mound of earth and stone overlooks the Pacific coast along the edge of the Chicama Valley. Unlike Trujillo, it is a quiet place. Agricultural fields dress its backdrop nearby. It has a name — Huaca Prieta, which, in Spanish, means “dark mound”. To the casual passer-by it strikes the impressive image of a distinctive greyish natural hill rising prominently behind the beach. But aside from its imposing physical appearance, Huaca Prieta stands apart for another very dramatic reason: within the underlying terrace that defines its foundation lies an archaeological record of human occupation that goes back as long ago as nearly 15,000 years B.P., with the astounding discovery of this very early occupation only recently coming to light. 

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Huaca Prieta means “dark mound”, which was built on a low late Pleistocene terrace between 7,800-3,500 years ago and since then used as a burial place for later cultures. Today it is used for shaman rituals. Buried in the terrace below the mound are maritime and terrestrial cultural remains dated from about 14,500 to 8,000 years ago. Courtesy Tom Dillehay

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The Huaca Prieta Story

Archaeologists first began uncovering the mystery of the mound when excavations began under Junius B. Bird in 1946–1947. He and his team excavated three test pits. Among their finds were complex textiles with designs representing mythological humans, snakes, crabs and condors, as well as stone artifacts such as pebble tools and flakes. While excavating, they encountered the remains of underground structures, some of them featuring burials constructed of cobblestones and an ash-water mix. Evidence also emerged, with objects such as fish net weights and fish bones, that suggested the ancient inhabitants were fishers and gathered shellfish, with organic remains also indicating they were agriculturalists, growing beans, squash, gourds, tubers, peppers, cotton and fruit.

But the latest, and perhaps most remarkable, chapter at Huaca Prieta did not unfold until 2006, when anthropologist Tom Dillehay of Vanderbilt University began excavations and investigations of the site with the late Peruvian archaeologist, Duccio Bonavia, and a multi-disciplinary team of scientists and specialists. (Dillehay is best known for his work and discoveries at Monte Verde in Chile, where evidence of early human settlement more than 14,000 years old was found in 1975, challenging the long-held Clovis theory that suggested the first human arrival in the Americas was no older than 13,000 years ago). “I was always fascinated by the work of Junius Bird at the site and by the incredibly distinct color and form of the mound located next to the ocean,” said Dillehay of the site. “I had never seen anything like it.”  Dillehay had been working on the north coast of Peru since 1976 and continued to visit the site, but a series of unanswered questions, and a tip from geologists who had previously examined the site suggesting it could possibly contain cultural material deep into prehistory, inspired him to renew investigations.

As a scientist, however, Dillehay’s interest went far beyond the prospect of discovering deep history. “The objectives were simply to better understand the economy, stratigraphy and chronology of the site with new questions and methods,” he continued. “We also planned a detailed interdisciplinary study focused on paleoecology and outlying settlement patterns in the area, including other Preceramic sites, and we wanted to produce detailed quantification and qualification of the faunal and floral remains.”

His investigations slowly made their way to accomplishing these goals. But little did he know what treasures awaited him and his team as they carefully and systematically dug their way down through the mound. “We had expected many of the findings, but we found many more and diverse items than Bird had found,” said Dillehay. The team uncovered exotic materials, as well as food and non-food remains, and countless flecks of charcoal that suggested, in the context of associated artifacts, ritual fires.  “Bird thought the mound was residential, like a midden,” said Dillehay, “but it was almost exclusively ritual and mortuary.” Many other well-preserved organic remains were uncovered, including textiles, cordage, and ornate baskets. The basket remnants consisted of diverse materials, including a local reed still used by basket makers today. Some of the baskets were remarkably sophisticated, featuring segments made from domesticated cotton, colored with what was determined to be one of the oldest dyes known in the Americas. Indeed, in 2016, 6,000-year-old dyed cotton fabric was discovered. Analysis showed that it was indigotin, an indigoid dye, the earliest documented use of indigo dye to date, predating the use of indigo in Egypt by 1,500 years. In addition, stone tools, including a variety of hooks and objects likely used for deep-sea fishing, were also found.

But equally exciting was the dating of the site, particularly the lower layers.

“We were very surprised when we started getting early dates underneath the mound and especially on the south end of the mound where Bird never excavated,” exclaimed Dillehay in his correspondence with Popular Archaeology. Radiocarbon dating techniques showed human occupation as early as nearly 15,000 years ago.

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Workers taking bucket loads of excavated sediments from a deep excavation unit to screens for sifting. Courtesy Tom Dillehay

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Archaeologists working at the 30 m depth level at Huaca Prieta. Courtesy Tom Dillehay

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An Early Society

It is no longer extraordinary to discover evidence of a human presence in the Americas before 13,000 years ago. A number of discoveries at disparate locations have attested to this — such as Blue Fish caves in the Yukon territory of Canada where archaeological remains suggest humans at about 24,000 years ago, Meadowcroft Rockshelter in western Pennsylvania, where stone tools were found to be as much as 16,000+ years old, and Monte Verde in Chile, the site of Dillehay’s excavations beginning in the 1970’s, with evidence suggesting human occupation as long ago as 18,500 B.P. These sites and discoveries name only a few that have emerged in recent years. The findings have supported the formulation of new paradigms for human migration into the Americas, adding the possibility that humans crossed by water, along coastal routes, in addition to the traditionally accepted inland routes (such as passage through the ice-free corridor from ancient Beringia after leaving Asia).  

Perhaps the biggest takeaway from the Huaca Prieta investigations thus far, outside of the early dates, is the realization that a relatively sophisticated society was emerging in the region long before the earliest great civilizations were taking shape in other areas of the world. Part of the foundation of that early civilization as exemplified by Huaca Prieta was in part because of the exploitation of multiple streams of resources, combining maritime and agricultural-based economies into an integrated strategy for survival and creating an economic surplus as the basis for the early, structured, urbanized centers that followed. 

“These strings of events that we have uncovered demonstrate that these people had a remarkable capacity to utilize different types of food resources, which led to a larger society size and everything that goes along with it such as the emergence of bureaucracy and highly organized religion,” said James Adovasio, co-author of the recently published study on Huaca Prieta and a world-acclaimed archaeologist at Florida Atlantic University. (It was Adovasio who conducted the pioneering work at the Meadowcroft Rockshelter in Pennsylvania, where some of the earliest evidence of human occupation in the Americas was found). 

Adovasio is one of the world’s leading experts in the analysis of ancient textiles and basketry. He focused particularly on the extensive collection of basket remnants excavated at the site.

“To make these complicated textiles and baskets indicates that there was a standardized or organized manufacturing process in place and that all of these artifacts were much fancier than they needed to be for that time period,” said Adovasio. “Like so many of the materials that were excavated, even the baskets reflect a level of complexity that signals a more sophisticated society as well as the desire for and a means for showing social stature. All of these things together tell us that these early humans were engaged in very complicated social relationships with each other and that these fancy objects all bespeak that kind of social messaging.”*

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Various unifacial flakes from basalt and andesite cobbles, dating between ~14,500-13,500 years ago. Courtesy Tom Dillehay 

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Above: Some of the exotic ritual offerings dated between 7,000-4,500 yrs ago: a, Spondylus fragment; b-c, turquoise fragments; d, malachite; e, Scleractinia sp. coral; f, rock crystals; g, ceramic fragments. Courtesy Tom Dillehay

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Textiles: Early cotton fibers were dated to around 6,200 yrs ago. The textiles shown here are dated to 5,500-4,000 yrs ago: a, Specimen 2009.154.02.B before (left) and after (right) it was washed with hexametasulfate to remove paste and reveal dark-blue warp stripes (left: photo by the author; right: photo by Lauren Badams); b, comparison of Specimen 2009.114.12 before (left) and after (right) washing it with hexametasulfate, revealing a gold color (photos by Lauren Badams); c, Specimen 2009.001.11 (front, back, and detail) of tapestry band with gold camelid hair; d, Specimen 2009.052.01.B, which was dyed with indigo (photo by Lauren Badams); e, Specimen 2009.114.08, which has overall red color (photo by Lauren Badams). Courtesy Tom Dillehay

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Basket remnants retrieved from the site were made from diverse materials including a local reed that is still used today by modern basket makers. More elaborate baskets included segments made from domesticated cotton and were colored using some of the oldest dyes known in the New World. Credit: Florida Atlantic University’s Harbor Branch Oceanographic Institute

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James M. Adovasio, Ph.D., D.Sc., co-author of the study and a world acclaimed archaeologist at FAU’s Harbor Branch, with a basket artifact from the site. Adovasio is one of the world’s foremost authorities on ancient textiles and materials such as those used in basketry. Credit: Florida Atlantic University’s Harbor Branch Oceanographic Institute

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Strata in Unit 15, showing late Pleistocene and early Holocene levels and radiocarbon dates. Courtesy Tom Dillehay

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Above: Profile of Unit 22, showing intact floors, fills, and radiocarbon dates. Courtesy Tom Dillehay 

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Above: a, photograph of burial HP08-01 on the south rim of the sunken circular plaza; b, cobblestone architecture of Tomb 8 containing HP08-01 on the rim of the circular plaza. Courtesy Tom Dillehay

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Moving forward, Dillehay, Adovasio and colleagues are convinced that Huaca Prieta, and sites like it, will open new windows on our understanding of how and why remarkably early monumental civilizations arose along the Peruvian coast, in addition to a better understanding of the full chronology of civilization in Peru.

“Huaca Prieta is located on the Sangamon terrace**, which also contains later occupations all the way up to the Colonial period, so that area has the entire history of Peru there,” said Dillehay. “As for the peopling of the Americas, the early material simply adds another site to the now longer list of Pre-Clovis locales in the New World.”

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Much more information about the discoveries at Huaca Prieta and neighboring sites in Peru can be obtained by ordering the book, Where the Land Meets the Sea: Fourteen Millennia of Human History at Huaca Prieta, Peru, now available at University of Texas Press.

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* https://popular-archaeology.com/issue/summer-2017/article/groundbreaking-discovery-of-early-civilization-in-ancient-peru 

** https://www.researchgate.net/figure/235707707_fig2_Figure-2-Mound-and-Sangamon-terrace-at-Huaca-Prieta-Note-the-seashore-in-the

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America’s Ice Age Hunters

By James Kensington

Zacatecas, Mexico — Until recently, few people other than the local villagers in the valley region below knew about this cave. Formed by natural forces in the face of a mountain slope some 1,000 meters above the valley floor, it saw a major transformation about 12,000 years ago when the initial cave entrance at least partially collapsed. Clearly, however, this did not stop the cave from harboring a variety of creatures small and large through time. Bats — thousands of them — made their home here. Over the past century, local farmers laboriously climbed the steep slope of the mountain over loose sand and gravel to reach the cave. Taking their packed donkeys up with them and into the cave, they gathered the guano (bat droppings) that coated the cave floor. Depositing it in large bags, as many as they could handle, they packed their animals with their haul and again traversed the rough trail, this time down and back to their farms below. Though routinely difficult, the trip was well worth it: guano was as valuable as water to them. It was a natural fertilizer, rich in nitrogen, phosphate, and potassium — essential for growing crops.

Known today as Chiquihuite Cave, it came to the attention of archaeologist Ciprian Ardelean of the University of Zacatecas in Mexico a little more than 10 years ago as he traveled about the region. At that time, he was conducting field research for his PhD. Searching for caves in northern and central Mexico that could potentially contain evidence of prehistoric human occupation, he would talk with local villagers who had personal knowledge of the region. A tip led him to explore the Chiquihuite Cave. What Ardelean found was the beginning of a remarkable 10-year journey of discovery within a limestone cave featuring two large interconnecting chambers, each 50+ meters wide and 15 meters high. Characterized with randomly distributed speleothems, the cave’s interior ceiling and floor landscape inclined downward away from the entrance toward the rear of the cave with roof-fall blocks of stone and debris flow deposits. During his exploration within, he found an area 50 meters from the cave entrance that was clear of roof collapse boulders, providing the opportunity for further investigation. Here, in 2012, he dug a test pit. Among other materials, as he had hoped, it revealed evidence of a past human presence. Most remarkable, however, were the results he obtained from the dating analysis. These finds were between 18,000 and 26,000 years old. This placed them at or before the Last Glacial Maximum (LGM), when ice sheets covered North America to its greatest extent — and, if the dating was right, it meant that humans had entered the Americas a whopping 10,000 — 15,000 years earlier than the oldest currently accepted dates in mainstream scholarship. The implications of the finding for anyone who knew anything about American archaeology and the earliest inhabitants of the American continents were extraordinary.

Could this be accurate?

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View of the Sierra El Astillero mountains where the Chiquihuite cave was found in 2012. Devlin A. Gandy

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Unprecedented

As the adage goes, extraordinary claims usually require extraordinary evidence. More finds were needed. So Ardelean and an international team of scientists went to work by extensively expanding the excavation, beginning in 2016. They knew this would be a dangerous and difficult task. Drug cartels controlled the area.

“It was an unforgettable experience,” said Dr Mikkel Winther Pedersen, a team geneticist from the University of Copenhagen who became a lead author of the excavation project research paper. “It is a very unsafe place to travel so we were accompanied by Mexican police officers in armored cars to the foot of the mountain. We left before sunrise to climb up to the cave so that we weren’t spotted.”* Additionally”, Pederson continued, “everything from water to food as well as sampling equipment had to carried up by us and 50 donkeys in order for us to stay at the excavation without having to descend each evening.” In essence, for the researchers like Pedersen, it was like a cave camping expedition. But Ardelean was accustomed to this. He had already spent a number of months in the cave like this for years before other specialists like Pedersen ever set foot inside.

Covering a total area of 62 square meters, the team proceeded to meticulously and systematically dig, recording all materials, features and finds encountered in the process. Digging from 2016 into 2017, they revealed a dissected cave floor that consisted of, in profile, a ten-foot column of six distinct layers of compressed, stable sediments — perfect for defining undisturbed spatial relationships of objects and for dating the finds. In all, they recovered 1,930 stone artifacts unmistakably identified as either stone tools or fragments related to stone tool making, as well as bone and other organic material. The stone artifacts included stone cores, flakes, bladelets, modified or used debitage, scrapers, points, and adzes. The abundance of bladelets and blade fragments suggested a microlith technology , a stone tool tradition that was commonly employed by humans from around 35,000 to 3,000 years ago to fashion spear points and arrowheads across Africa, Europe, Asia and Australia. More than 90% of the artifacts were manufactured from what the researchers described as “green and blackish varieties of recrystallized limestone”**, a material that did not belong to the petrology of the cave, and thus must have been selectively acquired from areas outside of the cave. All of these factors clearly pointed to lithics in the cave showing anthropogenic modification — these stone objects were the result of purposeful, intentional human activity. Equally important, the tools represented a “lithic industry with no evident similarities to any other Pleistocene/early Holocene cultural complexes known in the Americas”.** They were unique among all other stone tool cultural traditions discovered thus far on the American continents.

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The team was escorted by armed police in protection from nearby drug cartels and gangs. Mads Thomsen

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Locals with donkeys from the nearby town were hired to help transport water and food to the cave site. Mads Thomsen

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Professor Eske Willerslev, a key researcher and lead study author, and the team members ascending to the cave site which lies behind the tree line. Mikkel Winther Pedersen

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Team members entering the Chiquihuite cave. Devlin A. Gandy

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Team members eating lunch on the small platform around the Cave entrance. Mads Thomsen

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Stone tool found below the Last Glacial Maximum (LGM) layer, within Stratigraphic Component C, at Chiquihuite Cave. Ciprian Ardelean.

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Stone tool found above the Last Glacial Maximum (LGM) layer, within Stratigraphic Component B, at Chiquihuite Cave. This particular piece was made from a greenish crystallized limestone, typical of the Chiquihuite assemblage. Ciprian Ardelean.

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Stone tool found below the Last Glacial Maximum (LGM) layer, within Stratigraphic Component C, at Chiquihuite Cave. Ciprian Ardelean.

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How Old?

As exciting as the artifacts were, however, the researchers knew that none of this would have as much meaning without knowing or confirming when they were produced and used. Were any of these stone tools in this expanded excavation as old as those found in the earlier 2012 test pit? To determine this, they employed both radiocarbon and OSL (Optically Stimulated Luminescense) dating to bone, charcoal, and sediment samples taken from the excavation area, ensuring that sampling was spatially tight with the artifacts to assure association integrity of the artifacts with the sampled context. Using radiocarbon dating as their primary dating tool, they obtained 46 determinations from a total of 59 samples, and 6 OSL determinations as an independent control group from 8 samples. The confidence level for the dating accuracy and reliability among the scientists was high. Said Pedersen, “This is a very precise method for age estimation and often provides an age with a -+50-year accuracy…….samples of bone or other organic material found in the layers from top to bottom were dated, which provided a highly detailed chronology for all the layers.” Aside from the stone tools and some possible evidence of controlled burning within the cave, chemical residue analysis of the sediment also yielded data that suggested human activity within the cave.

The results of the dating?

Focusing on the oldest layers, the data suggested that humans were occupying the cave between 25,000 and 30,000 years ago, with the earliest artifacts dated to about 27,000 years ago — well within the LGM, when glaciers covered much of the American continent.

The Paleoenvironment

While much of the North American continent was covered with glaciers between 20,000 and 30,000 years ago, the image of a stark landscape characterized by ice and snow was not what the early inhabitants of the Chiquihuite Cave were likely experiencing, based on the data recovered by the research team. “The view from the cave entrance today overlooks mountain slopes covered by pine and different species of Yucca such as Joshua trees,” said Pedersen. “There is also a great look over parts of the valley and in the background you see the other mountains surrounding the valley.” Between 25,000 and 30,000 years ago, for the ancient hunters who sojourned here, the scene would have been similar, affording them a strategic view of the landscape and its game below. But there were a few differences. “From our findings,” Pedersen continued, “it seems to have been more forested which coincides [with a] climate [that] would have been colder……at times there would have been quite a bit more precipitation.” Inside the cave, a variety of fauna and flora thrived, or at least made their way into the cave over time.

To piece together this picture, a team of geneticists conducted eDNA analysis on the cave sediments. They donned full-body suits, including masks, gloves and shoe coverings to prevent contaminant DNA from their bodies and clothes from skewing subsequent test results. Pedersen and his team of specialists used delicate sterile tools and tubes to extract samples. This careful, protective process was essential, according to Pedersen, as DNA degrades over time, hence very ancient DNA would be in extremely low concentration after many thousands of years. The team obtained 31 DNA extractions from samples taken from 15 key stratigraphic units. They brought all samples back to the Globe Institute in Copenhagen, where state-of-the-art techniques, processes and equipment were used to retrieve the DNA from the samples and computationally analyze it. The analysis results helped them to reconstruct the paleoenvironment, indicating that the earliest dated periods featured a mixture of forest plant species such as junipers, firs, pine, spruce, grasses, rosins and Indian paintbrush. Through the millennia, the analysis also showed the cave was occupied by a variety of animals, including bears, rodents, birds, goats, and, of course — bats.

“Another objective was to see if we could retrieve DNA the humans may have left behind in the cave in order to determine who they were related to in the past – and hence understand where they came from,” said Pedersen. They found no human DNA — at least not within the samples taken. “This does not negate human presence at Chiquihuite Cave,” report the authors of the related study published in Nature, “as the probability of detecting ancient DNA from cave sediments has been shown to be low”.**

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Assistant professor Mikkel Winther Pedersen with team members carefully sampling the different cultural layers in the cave. Above photo: Mads Thomsen; Below photo: Devlin A. Gandy

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Assistant professor Mikkel Winther Pedersen from the University of Copenhagen sampling the cave sediments for DNA. Devlin A. Gandy

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Implications, and Other Sites

In sum, by combining the artifact, eDNA, and soil chemistry analysis, the researchers were able to build a preliminary albeit sketchy portrait of what was happening in this cave nearly 30,000 years ago:

Picture small bands of hunters sojourning in the cave. These were in essence nomadic campers, passing through as they moved on to new destinations. As Pedersen interprets the findings: “We think these early people would probably have come back for a few months a year to exploit reoccurring natural resources available to them and then move on…..probably when herds of large mammals would have been in the area and who had little experience with humans so they would have been easy prey.”* Therefore, the cave was not a permanent habitation place, where humans made their home year-round. They came and left through time on a periodic but persistent (“….. stone tools were found in all excavated strata.”)**basis, obviously adapted to higher altitudes and mountain environments, following the shifting game and their fortunes made in the valley below them. 

But this is not the only place where possible clues to a human presence of sojourning hunters have come to light. Far to the north, at Bluefish caves in today’s Canadian Yukon, scientists have uncovered cut bone that could tell a similar story. Among other finds, they found a horse mandible and caribou pelvis that showed tell-tale signs of human-made butchery cut-marks that were dated to 20,000 years ago. “The absence of hearth features and other markers suggest that the caves were used seasonally, probably as short-term hunting sites,” wrote author Jesse Holth about the site in the article, “Bluefish Caves: The Oldest Known First Americans?”, published in Popular Archaeology. Thousands of years ago, the site would have been located just east of most of ancient Beringia, the land bridge that connected Asia with North America during the Ice Age. Old Crow Basin, also in this region of the Yukon, has yielded fossils that show possible human-caused breakage of mammoth bones dated to 25,000 to 40,000 years ago. And thousands of miles to the south and east, there are six Brazilian archaeological sites dated older than 20,000 years ago. At the Brazilian site of Toca da Tira Peia, for example, scientists uncovered possible evidence of a very early human presence, including 113 stone artifacts within five soil layers, with the lowest layer dated to 22,000 years ago. None of these sites mentioned thus far are of course without dispute. Scholarly debate will surround these discoveries, just as it will for the Chiquihuite and Bluefish caves claims. 

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Horse mandible from Cave II at Bluefish : Cut-marks indicate removal of tongue with stone tool. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham

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If the findings at these sites and any new sites prove ultimately indisputable, the question then shifts more to searching for evidence in the paleoclimate record that might support the early dates. The broadly accepted view about when and how the first Americans entered the Americas has revolved in part around the changes in the glacial periods associated with the last glacial period of the Ice Age. During the LGM, the Cordilleran and Laurentide ice sheets covered much of Canada. However, during the warmer interglacial periods they retreated to create ice-free corridors along the Pacific coast and areas east of the Rocky Mountains of Canada. Scientists have long suggested that it was through these corridors that humans were likely able to cross Beringia or journey in stepped advances along the Pacific coast into the Americas. Exactly when and how these movements may have occurred has been a matter of debate for decades. The most widely accepted proposal has advanced the suggestion that a major entrance opportunity occurred around 15 – 16,000 years ago, after a “standstill” period (known as the Beringian Standstill Hypothesis), wherein the people who would eventually colonize the Americas spent between ten to twenty thousand years living on the Bering Land Bridge, a plain that connected the Americas with Asia during the Ice Age. Theoretically, at least some of the Beringians ventured east into the Americas when the climate warmed following the close of the LGM, the Bridge gradually becoming inundated by the melting ice and rising Bering Sea. 

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Demarcated region shows location of ancient Beringia, most of which is now inundated by the Bering Sea.

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With the results from Chiquihuite, however, Pedersen and his colleagues entertain the possibility that the ancestors of the Chiquihuite sojourners may have even entered the Americas before 30,000 years ago. With the growth of the ice sheets of the LGM commencing at 33,000 years ago, and maximum coverage not occurring until between 26,500 years and 19–20,000 years ago, pre-LGM conditions may have afforded an irresistible opportunity for early hunting bands. Those Ice Age hunters, following the migrating big game, could have eventually found themselves far east and south of ancient Beringia long before current scientists had ever thought possible.

Moving Forward

“The excavation is now closed, but the analyses continues,” wrote Pedersen to Popular Archaeology when asked what was next on their research agenda. “A lot of samples have been taken during the past 10 years and still remain to be processed. The big wish for the first samples analyzed for DNA was to identify the DNA from these ancient humans. While this hasn’t been found yet, we are still working on finding it and hopefully [we will] be able to identify who these people were related to.” In addition, future researchers will need to take another, closer look at other disputed sites across the Americas and investigate new areas and possibilities.

“We don’t know who they were, where they came from or where they went,” concludes Ardelean. “They are a complete enigma. We falsely assume that the indigenous populations in the Americas today are direct descendants from the earliest Americans, but now we do not think that is the case.

“By the time the famous Clovis population entered America, the very early Americans had disappeared thousands of years before. There could have been many failed colonizations that were lost in time and did not leave genetic traces in the population today.”*

Clearly, if the very early findings made at Chiquihuite and other sites in the Americas hold up after additional scrutiny, including new investigations and discoveries, mainstream scholarship may need to rethink how and when the first Americans arrived, and, equally intriguing — determine who they were. 

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Professor Eske Willerslev and professor Ciprian F. Ardelean at the entrance to the cave. Mads Thomsen

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*Humans in America as much as 30,000 years ago, suggest scientists, Popular Archaeology, July 22, 2020.

**Ardelean, C.F., Becerra-Valdivia, L., Pedersen, M.W. et al. Evidence of human occupation in Mexico around the Last Glacial Maximum. Nature 584, 87–92 (2020). https://doi.org/10.1038/s41586-020-2509-0

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In addition to the artifacts, fossils and skeletal remains have provided scientists with valuable evidence for human activity in the Americas during the late Pleistocene. Continuing the anthology, the following articles tell the story of discoveries, some still controversial, made primarily through the excavation and examination of ancient bones. The first article takes us tens of thousands of years before humans began their journey into the Western Hemisphere, with possible implications about humans who lived within what many scientists suggest were early American ancestral Siberian and East Asian homelands:

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Pushing the Prehistoric Fringe

By Jason Weaver

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For some, July and August in Siberia’s otherwise frigid Taimyr Peninsula could afford tolerable temperatures for walking about. At least that was the case for 11-year-old young explorer Yevgeny Salinder. During the summer of 2012, Yevgeny was living with his parents at the Sopkarga polar meteorological station on the Sopochnaya Karga (SK) Cape, where they were working. About 2,200 miles northeast of Moscow, the Cape is a stark sub-polar alpine landscape with mossy bogs, a moist tundra with waterlogged soils, and a home for the likes of animals like reindeer, wolves, arctic foxes, wolverines and mountain hare. For most of humanity, exploring this area might be at once both severe and exotic. For Yevgeny, however, a day’s adventure hiking about the Cape would not have been extraordinary. 

Until he found a dead mammoth along the way.  

Preserved for tens of thousands of years where it fell to its death in the permafrost, at least some of its remains were exposed enough by 2012 to have been visible to young Yevgeny on a coastal bluff off the eastern shore of Yenisei Bay—limbs sticking out of the frozen mud where a river enters the Yenisei Bay just 3 kilometers away from his station home.

It was like finding buried treasure.

After his return, he told his parents who, recognizing the potential rarity and import of the discovery, brought it to the attention of those who would know something about such things—like Alexei Tikhonov of the Russian Academy of Sciences in St. Petersburg. Tikhonov is a zoologist by education, but he is perhaps best known for his recent discoveries and published research related to paleontological finds through various excavations at arctic and subarctic locations. Leading a small team in late September of 2012, Tikhonov carefully excavated the carcass from its natural grave. In the process, more of its features became apparent—a nearly complete mammoth, with the right half of the carcass still retaining soft tissue, including skin, hair, one ear and even male reproductive organs. Weighing in at more than 500 kg, it turned out to be among the best-preserved mammoths ever found. The excavated remains were sent for cold storage in nearby Dudinks and then shipped to St Petersburg in early May of 2013. 

A Pleistocene Hunting Scene

The most tantalizing findings, however, did not occur until after the scientists dated the bones and began examining them up close. Now popularly nick-named ‘Zhenya’ after the boy founder, researchers determined that the SK mammoth was about 15 or 16 years old when he died at least 45,000 years ago, based on radiocarbon dating. The likely cause of death—human hunting. 

This was revelatory, as up until now no humans were known to have existed in the Arctic this long ago. “The [new Yenisei Bay] site is much older than everything known before in the arctic regions, and it is clearly located farther north from the areas where sites of that age have been found,” said Vladimir Pitulko, also of the Russian Academy of Sciences, who examined the remains in detail. “It is about 20 degrees north (about 1900 km, or 1300 miles) of any site of comparable age…… and this is a big change.”

So how did Pitulko and his colleagues come to suggest that Zhenya met his fate by human hunters?  

After closely examining Zhenya’s bones, including the left scapula, several ribs, jugal bone, and right tusk, Pitulko could come to no other conclusion than that they bore marks characteristic of wounds inflicted by a weapon and butchering marks left by stone tools. He knew this because at least one of the marks exhibited features very similar to those he found on a Pleistocene wolf humerus from excavations he conducted at Bunge-Toll in the middle Yana river in the western part of the Yana-Indighirka lowland (in westernmost Western Beringia), years before. The wolf remains had been found among the remains of other Pleistocene megafauna, such as mammoth, bison, reindeer, and rhinoceros. Using high-resolution X-ray computed tomography done by Konstantin Kuper at the Budker Institute for Nuclear Physics in Novosibirsk, Pitulko and colleagues could see a clear bone injury caused by penetration of a sharp implement with a conical tip. “The tool penetrated the bone deeply, taking pieces of cortical pieces inside the bone, which means it was a powerful blow,” said Pitulko. And now, some years later, Zhenya’s bone marks were likewise telling. “One of them was found on the inner side of the jugal bone (cheek bone) which was still attached to the skull. There is no natural or taphonomic reason for such an injury — this was not a bone pathology, it was not the result of carnivore chewing and it was not left by the excavation process — therefore we may expect it to be a result of human contact,” said Pitulko.  After X-ray computer tomography conducted by Konstantin Kuper, the researchers were actually able to determine the inflicting weapon’s shape and size, enough to even reconstruct the shape of the tip that penetrated the bone. “It had a thinned symmetric outline and was relatively sharp,” continued Pitulko. “In most cases, bone or ivory weapons have a conical tip that is symmetric and quite acute (~30° to 40°) at the end, but they are [usually] relatively fragile and often break as they penetrate bones. In this case, the tool resisted breaking and inflicted injury on the cranial bones. The blade retained its weapon characteristics and retained enough energy to penetrate the cheekbone surface deeply into the bone. The blow was evidently very powerful and was suffered by the animal from the left back and from top down, which is only possible if the animal was lying down on the ground.” Pitulko suggests that the blow was likely an attempt intended for the base of Zhenya’s trunk, a hunting practice still used by elephant hunters today to cut major arteries and cause mortal bleeding.  “This blow becomes necessary,” he maintains, “after the animal has been sufficiently injured, and the SK mammoth (Zhenya) displays numerous injuries in the thoracic area (the ribs and the left scapula). The most remarkable of them is found on the fifth left rib. This is an incision or cut mark left by some sharp tool slicing down. This pattern is very typical on mammoth bones, specifically on ribs, found [for example] at the Yana site.”

Overall, Tikhonov, Pitulko and colleagues suggest a scene where Zhenya was encountered by human hunters about 45,000 years ago, wounded/ brought down and killed, and then butchered immediately thereafter in place. Cut marks clearly made by cutting tools were evidenced on the left scapula and ribs, and even the right tusk showed signs of bone removal of a nature that suggested the possibility that the hunters fashioned ivory cutting tools from Zhenya himself.

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Excavations of the SK mammoth site in late September of 2012 near Sopochnaya Karga weather station at the Yenisei river mouth. Photo by Aleksei Tikhonov

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SK mammoth (‘Zhenya’) unearthed. Sergey Gorbunov is excavating the left side of the carcass in the head area. Photo by Aleksei Tikhonov

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The SK mammoth (‘Zhenya’). Aleksei Tikhonov (in the middle, and his field crew). Photo by S.V.Gorbunov

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Selection of bones collected by Tikhonov at the Bunge-Toll site. Note the wolf humerus (top left) positioned by the injuried side up. Photo Aleksei Tikhonov

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Aleksei Tikhonov (left) and Vladimir Pitulko discussing injury on the jugal bone of the SK mammoth at Zoological Museum (RAS), St Petersburg. Photo by Elena Pavlova

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Cut mark on the SK mammoth 5th left rib. Photo Pavel Ivanov

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Documenting human caused injuries on the SK mammoth scapula at the Institute for the History of Material Culture, RAS, St Petersburg. Pavel Ivanov and Vladimir Pitulko (on the right). Photo by Elena Pavlova

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The Significance and Implications

Paleolithic records of humans in the Eurasian Arctic are relatively scarce. Only a few sites in this region have yielded clues to an early human presence. In mainland arctic Siberia, the site of Berelekh, discovered by Nikolay Vereschagin in the early 70s, was for years the location yielding the oldest evidence for human migration into the arctic regions. It dated to about 13,000 years ago. But in 2001 another site in Siberia, known as Yana, produced evidence of a human presence dating back to about 27,000 -30,000 years. Excavated by archaeologist Vladimir Pitulko, also of the Russian Academy of Sciences, it yielded tools made from rhinoceros horn and mammoth tusk, as well as hundreds of other stone artifacts including choppers, scrapers and other biface implements. “But I never thought that even this was the final age estimate for human migrations into the arctic,” said Pitulko.

So Zhenya and the SK site have buttressed the site researchers’ suggestion that people were present in the central Siberian Arctic by about 45,000 years ago. At this time, according to Pitulko, mammoth hunting by modern humans probably became a critical element in human survival in the harsh environment and landscape of what is today Siberia. Like the modern-day elephant, the mammoth would have provided a critical source of food, fuel (dung, fat, and bones), and raw material for construction and hunting weapons and tools for processing, all the more important in the open landscapes of the Northern Eurasian steppe, which is mostly tree-less. Removed from the hunted dead carcasses of their mammoth prey, “ivory became a substitution for materials used for shafts and points long and strong enough for killing large animals, not necessarily the mammoth,” said Pitulko. “Such tools are found elsewhere in the Upper Paleolithic, and this includes even full-size spears of ivory which are known from [the sites of] Sunghir, European Russia or from Berelekh, Siberia. This innovation became a really important discovery for humans and finally helped them in surviving and settling these landscapes.” 

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Worked tip of the SK mammoth tusk. Photo by Pavel Ivanov

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Field study of the bones collected at the Yana site from the Yana mass accumulation of mammoth (August 2012) – looking for human impact. Photo Elena Pavlova

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Pitulko surveying exposures in Yana river. Photo Elena Pavlova

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Thus, according to the researchers’ report, advancements in mammoth hunting likely allowed humans to survive and spread widely across northernmost Arctic Siberia at this time, representing an important cultural shift – one that likely facilitated the arrival of humans in the area close to the Bering land bridge, providing them an opportunity to enter the New World before the Last Glacial Maximum. 

“This is especially important for questions related to the peopling of the New World, because now we know that the eastern Siberia up to its arctic limits was populated starting at roughly 50,000 years ago,” says Pitulko. “Until 15,000 years ago, sea-level (though changing) still remained low, which is clear from appropriate dates on terrestrial animals in the New Siberian islands. This presumes that the Bering Land Bridge existed probably most or part of this time, so the New World gate remained open…….The history of the territory which we call Western Beringia is of particular interest since it is close to the Bering Land Bridge area and then everything that was going on in this area is related (or can be related) to the question of the peopling of the New World. Most of the Eurasian north, including Western Beringia, was unglaciated [at this time] and available for humans.”

Could modern humans have crossed over to the New World from here in these early times?

“Probably yes,” says Pitulko. 

But did they?

Pitulko recognizes that there is much more work to do, and additional finds that need to be made, before this question can be answered and a conclusive picture of human habitation in these regions can be drawn. In any case, for now, a new stage is set for going forward.

“These finds change our minds about possible options and this is going to provide a new stimulus for further research.”

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Bluefish Caves: The Oldest Known First Americans?

By Jesse Holth

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In 1977, Canadian archaeologist Jacques Cinq-Mars spent 10 years leading the excavation of a uniquely important site known as Bluefish Caves in Yukon, Canada. What he and his team discovered there eventually became what is today one of the most compelling, albeit controversial, chapters in the ongoing search for the first Americans………..

Cut-Marks in the Bones

The Bluefish Caves site consists of three karst (limestone) caves, located about 50 kilometers away from Old Crow village in northern Yukon. The Caves – like the HMS Terror site in Nunavut, and so many others – were already known to local First Nations members in the area. “The Vuntut Gwitchin [people] knew about the caves and visited the site many times,” says Lauriane Bourgeon, a researcher who has been studying ancient remains recovered from the caves. But it was the Cinq-Mars expedition that conducted the first archaeologically controlled investigation of the site, leading to the recovery of a wealth of faunal remains, including fish, birds, and mammals, as well as around 100 lithic artifacts, including microblades, cores, burins, small flakes, and other debris. When Cinq-Mars and his team radiocarbon dated the artifacts, the results were shocking: they appeared to be close to 25,000 years old.

This new evidence challenged the widely held theory that humans didn’t arrive in North America until much later. Not surprisingly, Cinq-Mars’ work was largely dismissed by much of the scientific community. That is, until decades later, when Université de Montréal’s Ariane Burke and Lauriane Bourgeon of the Hominin Dispersals Research Group (HDRG), and Dr. Thomas Higham, Deputy Director of Oxford University’s Radiocarbon Accelerator Unit, returned to study the faunal collections, now housed at the Canadian Museum of History.

One of their objectives was to re-determine radiocarbon dates for human activity at Bluefish Caves. The first step was to establish which bones were culturally modified, and which bones were marked as a result of natural processes. Since striations and breakages can be produced by rock abrasion, archaeologists must carefully and systematically identify cut-marks made by humans – and separate them from markings that merely seem like human activity, but can be explained by other events.

Misleading cut-marks are often produced by carnivores, for example, whose jaws can create bone breakage and flaking that resemble human attempts at marrow extraction. One way to tell these markings apart is by the presence of other pits and punctures scoring the surface, created by carnivore activity. The bones may also be accompanied by bits of digested bone, left behind from the carnivores that consumed it. One of the most distinctive features of carnivore activity is the U-shaped tooth marks they tend to score into the bones.

Researchers evaluated and recorded such tooth marks for every specimen – with carnivore activity as an alternate explanation, these markings could not be used as evidence for definitive human activity. Bones that appeared to have been damaged by weathering, as well as biological agents like rodent gnawing, were also removed from the group of potential human cut-marks. While it’s possible these other processes may have simply obscured relevant cultural modification, scientific inquiry mandates a greater degree of certainty in the data. Therefore, the researchers used a set of six criteria for each potential cut mark, to determine which ones could have been the result of human butchery.

Searching for evidence of human modification can often be like finding a needle in a haystack. In this case, a whopping 36,000 mammal bones were examined from the caves designated as Bluefish Caves I and II. While researchers determined that the vast majority of samples were the result of carnivore activity – wolves, lions, and foxes were among those responsible for the bone accumulation – both caves also contained human-modified bones. The team postulated that Canids used the caves for den sites in the spring and summer, and that human occupation at the caves was sporadic and brief.

Biological and natural geological processes can present an obstacle when identifying cut-marks. Of the specimens from Cave II, for example, root etching was discovered on over 70% of the bones. Root etching is caused by the excretion of humic acid from plant roots, which leaves dendritic grooves in the surface of the bone. In Cave I, the more significant problem was abrasion – this had caused damage to 57% of the bones.

Ultimately, the researchers were able to determine that fifteen samples were definitively modified by humans, and twenty more were considered “probable” examples of cultural modification. The activities documented by the cut-marks on the bones included skinning, dismembering, and defleshing. The species represented in the human-modified samples included horse, caribou, wapiti (elk), and possibly Dall sheep and bison, as well as a bird scapula.

Six of the cut-marked bone samples were selected for radiocarbon dating, and the results yielded dates ranging from 24,000 to 12,000 cal BP. The oldest specimen was a cut-marked horse mandible from Cave II – this evidence, along with a caribou pelvis (also from Cave II) confirms a human presence dating to 24,000 – 22,000 cal BP. The caribou bone showed signs of filleting, while markings on the horse mandible were consistent with the removal of the tongue. Previous analysis on one of the horse’s teeth had also showed that it was killed in spring or summer, indicating a human presence during the warmer seasons. These findings are significant because they suggest that humans were, at least sporadically, living in North America during the Last Glacial Maximum (or LGM) and not after, as previously thought.

The human presence at Bluefish Caves also spans over 10,000 years – the caves were used on several occasions (or more) during the frigid cold of the LGM (then the Pleistocene) and into the Holocene. Three bone specimens from Cave I were dated to between 22,000 and 15,000 cal BP: a horse humerus, a horse metatarsal, and a caribou metacarpal. The humerus and metacarpal show marks from filleting activity, and the metatarsal shows signs consistent with the stripping of tendons. The youngest specimen, dating to 12,000 cal BP, was an unidentified bone fragment with signs of filleting. While the species couldn’t be confidently identified, researchers suggested it could be a wapiti bone, since other cut-marked wapiti bones were discovered in the same cavity.

While root etching, scavenging, and other biological and natural processes likely destroyed much evidence of human activity, we nevertheless now have definitive proof of human occupation at Bluefish Caves. The absence of hearth features and other markers suggest that the caves were used seasonally, probably as short-term hunting sites. This is the case for several Beringian cave sites, including Alaskan examples like Lime Hills Cave, Lower Rampart Cave 1, and Trail Creek Caves. By dating the cut-marked bone specimens from Bluefish Caves, HDRG researchers have provided archaeological support for what is known as the “Beringian standstill hypothesis.”

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Horse metatarsal from Cave I: Cut-marks from stone tools indicate possible tendon stripping. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham 

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Caribou metacarpal from Cave I: Cut-marks from stone tools indicate filleting. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham

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Unknown long bone fragment from Cave I: Possibly Wapiti bone, cut-marks indicate filleting. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham

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Caribou coaxal bone from Cave II: Cut-marks indicate filleting activity. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham 

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Horse mandible from Cave II: Cut-marks indicate removal of tongue with stone tool. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham

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Horse humerus from Cave I: Cut-marks from stone tools indicate filleting. Image courtesy Lauriane Bourgeon, Ariane Burke, and Thomas Higham

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The Standstill and the Earliest Americans

The standstill hypothesis proposed that a genetically isolated human population existed in Beringia, from at least 23,000 to 15,000 cal BP, before eventually spreading into North and South America after the LGM. While human activity had already been documented in Western Beringia, from Yana River sites dating to 32,000 cal BP, there was little evidence to support the theory from Eastern Beringia. That is, until Bluefish Caves, which now verifiably indicate that people were in Eastern Beringia by at least 24,000 cal BP, during the LGM.

According to the theory, Central Beringia would have been the primary habitation zone for a human population until it was submerged at the end of the Pleistocene. Even during the LGM, Central Beringia would have been habitable – with warmer, humid conditions and even occasional shrubs and trees, humans would have had access to both fuel and food. Rising sea levels would eventually push the population inland; unfortunately, this also means any evidence of human habitation in Central Beringia is likely destroyed, degraded, or still underwater.

It’s possible that Bluefish Caves was located at the eastern border of this population’s range. Seasonal hunting parties, venturing out of the core range and into the steppes of Eastern Beringia, would explain intermittent visits to sites like Bluefish Caves. This matches the data recovered, which indicates irregular human occupation over a long period of time. Researchers have proposed that the standstill population was fairly small – tens of thousands at the most – based on both archaeological and genetic evidence. After the LGM, as the climate improved, it’s believed that the population increased and caused new expansions into North America. Humans were still using Bluefish Caves, as documented by the cut-marked bones, but became reliant on different species (such as caribou, bison, and wapiti) since others, like the horse, had become extinct by about 14,000 cal BP.

Around this same time, the warming climate allowed an ice-free corridor to form between the Laurentide and Cordilleran ice sheets. Long since believed to be the route that humans took to migrate from Beringia down into North America, the corridor wouldn’t have been suitable for human travel until 13,000 or 12,500 cal BP. Many archaeologists now suggest that these early inhabitants of Beringia likely travelled down the Pacific coast instead, as early as 16,000 cal BP. Archaeological evidence supports this theory, showing that humans settled south of the ice sheets before the ice-free corridor formed.

Bluefish Caves is not only the oldest known human habitation site in North America – it was also used sporadically for over 10,000 years, and provides evidence of a potential “standstill” population in Beringia during the LGM. It appears that humans survived and subsisted off the land bridge for an extended period of time, creating a genetically distinct population, and only began to migrate when sea levels started rising. As the climate warmed up, more people were able to survive, creating a strain on resources and causing expansion into North America. It’s possible the standstill population travelled along a coastal route, leaving evidence south of the ice sheets. Or, some other seafaring group or groups may have travelled there first – leaving evidence at sites like Buttermilk Creek Complex in Texas and Monte Verde in Chile – and the standstill population followed the ice-free route later.  Burke confirms there is “much speculation about possible coastal dispersals,” noting that “the discovery of very early Clovis sites in North America… occur too close to the presumed opening of the ice-sheets to explain their geographical distribution.” According to Burke, “more survey work will be necessary – both in Canada and in eastern Siberia – in order to find more material to support the standstill hypothesis.” Although the theory doesn’t directly address subsequent migration routes, if it can be further substantiated we will be one step closer to determining the settlement patterns of North America’s first humans.

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The Extraordinary Case of the San Diego Mastodon

by James Kensington

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When news of the published study report in the prestigious scientific journal Nature broke, it became a bombshell headline for science media reporters. “Humans in California 130,000 years ago? Get the Facts,” flashed one widely read headline by National Geographic — “A 130,000-year-old archaeological site in southern California, USA,” reported the study abstract from Nature — “Ancient humans may have reached Americas 100,000 years earlier than thought,” posted USA Today. These were but a fraction of the published stories.  

To be certain, the authors of the report, including Thomas Deméré, Steven Holen, Kathleen Holen, and other scholars and scientists, knew this would be grist for scholarly skepticism and criticism for years to come. They were braced for it. But the evidence, to them, after years of study, was compelling enough to move forward with their results in a public way. They knew the implication of their study was enormous — humans, or human-like creatures — hominins — were on this continent, at least in the present-day San Diego area, well more than 100,000 years earlier than the earliest generally accepted dates for the first peopling of the Americas, currently established at around 14-15,000 years ago, or based on the recent Bluefish Caves discoveries, possibly at least 24,000 years ago. A very exciting discovery, if one could ignore a legion of scholars shaking their heads in skepticism. 

The Discovery

The story began in November 1992, when workers under a California Department of Transportation (Caltrans) highway construction project exposed something curious while excavating with a backhoe on State Route (SR) 54, where San Diego borders National City. As State law requires, paleontologists from the San Diego Natural History Museum’s PaleoServices Department were on site doing routine monitoring of the grading activities, in case any fossil material might be encountered. It wasn’t long before the paleontologists justified their presence, and in a very exciting way. As field paleontologist Richard Cerutti watched the caterpillar backhoe excavate through the sandy soil, he spotted what appeared to him to be a horizontally oriented mammoth tusk bone. Construction work in the vicinity of the finds was immediately halted, and the nature of the excavation changed from one using heavy construction and excavation equipment to one using much finer methods — methods typically used by paleontologists and archaeologists. Excavations continued on and off over a period of five months, and together with the San Diego Natural History Museum’s PaleoServices Director Dr. Tom Deméré and a team of site investigators, the team encountered more fragments, including molars, clearly revealing that what they were looking at were actually the remains of a mastodon, a large mammal that inhabited the region during the Pleistocene, becoming extinct about 10,000 -13,000 years ago.

But there was something else that was tantalizingly peculiar about these remains. As they continued to excavate, they could see that many of the bones were fractured or broken in a way that was not typical of bones broken by the forces of the natural environment. Said Kathleen Holen, Director for the Center for American Paleolithic Research in Hot Springs, South Dakota, and one of the authors of the study: “The fragments were found to be clustered in two distinct areas around rocks. The heavy limb bones, which are useful for making tools, were smashed and broken up, but the lighter bones like ribs and vertebra were more complete. We found characteristic marks on the bone surfaces, notches and scars where flakes of bone had been removed, and this is characteristic of bone that has been broken by percussion, that is, with hammerstones.  We also found cone flakes that occur characteristically around the point of impact, much like when you see a B-B strike a window — those circular patterns break off in flakes. In our experience, these bones were broken in patterns usually associated with human modification, broken while they were still fresh.”*

Added to this was the discovery of several large stones found within the same sediment layer as the bones. Finding large stones was not unusual. But finding them located precisely where the modified bone fragments were located was peculiar. “We found stones that were located right within the concentrations [two separate clusters] of the mastodon bone fragments and flakes and the stones and bone fragments could be refit back together so it showed that whatever happened, it was all in the same location,” continued Holen who, along with her husband scholar and study co-author Steven Holen, joined the team efforts in 2008. “We found marks on the rocks that were characteristic of them being used as pounding tools. So there was pounding evidence on both the rocks and on the mastodon bones. Then we saw other signs of human behavior — for example, the location of one of the impacts indicated that there was cooperation between at least two people to steady this bone on an anvil and then break it.”* 

The team considered the possibility that this was all a result of natural processes. But the Holens and colleagues could not fit what they saw into scenarios based on natural causes. “We found no evidence that carnivores have interacted with the bones or that there had been a trampling event that broke the bones and there is no evidence of flooding that would have caused the rocks to break the bones because the flooding would have washed away these smaller fragments that were still right with the stones.”

They knew this would not be enough to draw any conclusions, so to confirm or deny their hunch, they turned to additional expertise. One of these experts was Dr. Dan Fisher, a paleontologist from the University of Michigan — an expert on mastodon fossils. Fisher had significant experience excavating mastodon and mammoth sites that exhibited bones broken while they were still fresh. Carefully examining the site and the evidence, he concluded that there were  clear signs that the bones had been broken by percussion. 

The logical question followed: Were the stones within the clusters really used as tools by humans to break the bones? To answer this question, in 2015 they sent the stones to a well-recognized expert on use-wear analysis, Dr. Richard Fullagar, an archaeologist at the University of Wollongong in New South Wales, Australia. Fullagar examined the stones and compared them to known stone tools, as well as other stones used by the research team to break open fresh elephant bones as an experiment. His conclusion: The stones showed the same abrasions, fractures, and marks that could only come from repetitive impact. To help with further study of the samples, they employed Dr. Adam Rountrey, a colleague of Fisher’s, to produce 3D digital models. 

The researchers were unanimous. This looked like an archaeological site — a site, no longer occupied by human or animal, with evidence of past human activity.

But what about that other critical question — the age of the site? 

Once they had solid samples to be sent for dating, the team did not waste any time. They were sent to USC geologist Dr. Richard Ku for analysis using the radiometric (U-Th) dating techniques of the time (1992/1993). On December 29, 1993, Ku called Deméré with some startling news — a caliche (sedimentary rock) sample from the Cerutti mastodon sediment layer yielded a date of about 190,000 ka. Deméré nearly fell out of his chair. In January, 1994, Ku sent the formal letter report of the dating results. But the Cerutti mastodon site, as far as the mainstream scholars were concerned, joined the plethora of American Paleoindian sites considered as questionable in terms of age. It wasn’t until almost two decades later when they again sent samples for dating, this time to Dr. James Paces, geologist and geochronologist at the U.S. Geological Survey. From 2012 to 2015, Paces applied more advanced and reliable Uranium radiometric dating analyses on “prepared multiple specimens, performing digestions, chemical separations and purifications, and complete isotope analyses on nearly 100 individual subsamples”.** The result: The mastodon bones and associated stones were buried in sediments that are about 130,000 years old, give or take 9,400 years. 

With this, the research team was ready to go public again, and in 2016 they submitted their report to Nature for review. The report was published in 2017, and the news broke in major venues across the world — humans may have been in the Americas more than a whopping 100,000 years before the earliest known dates for the first peopling of the continents. 

Deméré, the Holens, and the rest of the research group anticipated that this would ignite controversy. And sure enough, it generated a firestorm of criticism across a broad spectrum of the scholarly community, especially among scientists involved in First Americans research.

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San Diego Natural History Museum paleontologist Richard Cerutti (after whom the site was named) observing an excavator expanding the Cerutti Mastodon site, March 1993. Courtesy San Diego Natural History Museum. 

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View looking east of the Cerutti Mastodon site, November 1992. Courtesy San Diego Natural History Museum.  

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Caltrans archaeologists Karen Crafts, Chris White, and Don Laylander excavating fossils found at the Cerutti Mastodon site, November 18, 1992. Courtesy San Diego Natural History Museum.

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Brett Agenbroad (top left), Larry Agenbroad (left), James Mead (bottom left), and Dr. Tom Deméré excavating fossils found at the Cerutti Mastodon site, December 29, 1992. Courtesy San Diego Natural History Museum.

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Vertebrate paleontologist Dr. James Meade and Director of PaleoServices Dr. Tom Deméré observing an exposed rib and femur ball in the upper right corner of excavation unit D-3 at the Cerutti Mastodon site. Courtesy San Diego Natural History Museum.

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Mastodon skeleton schematic showing which bones and teeth of the animal were found at the site. Courtesy San Diego Natural History Museum.

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The Archaeological Site That Can’t Be

Clearly, the Cerutti Mastodon (CM) site findings up-ended the emerging concept on the timing of the first peopling of the Americas in a major way, and the big names in research on the subject were not going to let this go unchallenged. But the dating itself was actually not the biggest problem for the critics. The process and techniques used on the CM site dating are broadly considered to be the most reliable and accurate that could have been done to date. “Basically we have to believe the date,” says Warren Sharp, an expert on radiometric dating. “The date is not the question in this study. There have been lots of people that have claimed that they had some kind of archaeological evidence for people earlier than 15,000 years ago or so. But if this really passes muster, then I think all of those sites and all of those claims are going to be looked at with new eyes and people are going to not just dismiss them out of hand.”* 

So with the age set aside as a point of contention, the real problem lies in the interpretation of the site as an archaeological site — a location that bears evidence of human occupation or activity. The most salient critiques have revolved around a widely held principle: that extraordinary conclusions or findings require an extraordinary preponderance of credible evidence. They have to meet several crucial tests, namely, that “(1) Archaeological evidence is found in a defined and undisturbed geologic context; (2) Age is determined by reliable radiometric dating; (3) Multiple lines of evidence from interdisciplinary studies provide consistent results; and (4) Unquestionable artifacts are found in primary context”.*** 

One of the biggest points of contention centers on the suggestion that the ‘hammerstones’ and ‘anvils’ are indeed artifacts, the fourth test as noted above.  “To demonstrate such early occupation of the Americas requires the presence of unequivocal stone artifacts,” says Michael R. Waters. Waters is a prominent scholar on the archaeology of early Americans and has held the Endowed Chair in First American Studies at Texas A&M University, the directorship of the Center for the Study of the First Americans, and serves as the Executive Director of the North Star Archaeological Research Program. Waters has been at the forefront of research with his discoveries of evidence of early American occupation as much as 14,000 – 15,000 years ago at such locations as the Debra L. Friedkin site in Texas and the Page-Ladson site in Florida. Regarding the Cerutti Mastodon site, however, he asserts “there are no unequivocal stone tools associated with the bones.” The stones described at the Cerutti mastodon site simply don’t meet the stringent standards required to be designated as artifacts, he maintains. 

Tom Dillehay, the renowned anthropologist with Vanderbilt University who was key to the claimed discovery of a 14,500-year-old human presence at Monte Verde, Chile, agrees. He says that the Cerutti site study does not fully rule out the possibility that the stones were moved to the site by natural processes, and that the wear patterns on the stones may have been the result of the stones bumping against other stones in a moving stream. 

“Holen has made similar claims for other sites he has worked on in the Midwest,” says James M. Adovasio, the archaeologist who led the famed excavations of the Meadowcroft rock shelter in Pennsylvania, where evidence of human activity dated to at least 16,000 years ago was discovered. “These sites have also been roundly critiqued because he has not effectively ruled out other means by which the bones may have accumulated. This is perhaps the biggest problem with all such sites. Specifically, is there a natural, non-anthropogenic, possible explanation for the bone accumulations and their patterning? In the case of Cerutti and the Midwestern localities, this question has not been answered.”

Another argument against the Cerutti site raises the problem of a clear absence (thus far) of bifacial stone tools, a technology that was well-established by 130,000 years ago and would likely have been transported to the New World by its original prehistoric Old World settlers coming from the west. “Though bifacial technology is well developed at this time in the Old World, there is not a shred of it at Cerutti,” says Adovasio. “It is obviously not absolutely necessary that bifacial technology be present on such a site,” he adds, but “all of the bona fide Old World sites of this time period exhibit such materials”. 

And then there are the bones. Skeptics are not convinced that the large bones, including teeth, were broken by humans using the ‘hammerstones’ and ‘anvils’, as the study suggested. “If, as the authors claim, they are splitting bone for marrow and/or tool production,” says Adovasio, “why are all of the pieces from these processes still there? They all retrofit. Additionally, no one splits teeth for marrow!”

Another voice of caution has been expressed by Briana Pobiner, a paleoanthropologist at the Smithsonian Institution and a noted expert on recognizing human activity through the examination of bones.

“What concerns me most about the CM site is a lack of any butchery marks on the mastodon fossils – and the lack of stone tools,” she says. “Interestingly, at ethnographic and some archaeological proboscidean (elephants and their extinct relatives) butchery sites you sometimes don’t see any butchery marks because these animals are so big that you can easily cut meat off of them without leaving any butchery marks — but that’s when the goal is meat processing. To break open the bones for marrow, you need to strip all the meat away, including the connective tissue (like periosteum and cartilage) surrounding the bone, which can be up to 3mm thick on elephants. It seems odd not to see any evidence for that kind of processing [at this site] — nor for the tools used to do that processing.” However, she added, “perhaps the bone could still be “fresh” after the connective tissue has decayed away. In a 2015 paper, Haynes and Klimowicz noted that elephant limb bones can retain grease for up to 3 years, and retention of grease likely means spiral fracture” when attempting to break open bones for access to marrow. This contrasts with bones when they are dry and past the fresh stage, when breakage is characteristically “jagged, longitudinal, or parallel to the long axis of the bone”.  

But Pobiner is not totally convinced that the Cerutti bone spiral fractures were necessarily caused by humans. 

“Researchers used to always attribute spiral fracture to human activity, but a few decades ago it was demonstrated that carnivore chewing and other activity can spirally fracture bone –- it’s indicative of the timing of breakage, not the cause of breakage,” she added. “Gary Haynes, an expert on proboscidean butchery, has studied hundreds of natural elephant bone sites in southern Africa, and found that at some sites up to 62% of the limb bones are spirally fractured” by natural causes.

The Defense

The study authors, on the other hand, are confident they have a strong case for further testing and investigation.

“Only a few of them produce the full banquet of evidence that would be convincing to a really wide range of people,” says Fisher, a key participant and co-author of the study report, about sites like the Cerutti case. “I think the Cerutti site produces that full banquet in a way that very few others do. At the same time the nature of the evidence that is there is completely parallel, completely consistent with patterns that we see at other sites. So not only do I not have a problem with interpreting this as human activity, but I feel I would be intellectually dishonest to turn away from this and say, well, it can’t be human activity only because it’s too old. It’s the same as we see in the best cases where we argue for human activity.”

And while some of the best scientists around the world are itching to poke holes in those statements, the Cerutti site team points to a list of reasons why they think their case is convincing. As published for the media by the San Diego Natural History Museum, the researchers had the following to say:

Regarding the argument that the finds may have been caused by other natural or geological events: 

— The pattern of the mastodon bone bed differs from that of the skeletons of horse, dire wolf, and deer discovered in other strata within the same Pleistocene rock;

— the occurrence of large and small bones together with five large cobbles within an otherwise sandy silt horizon indicates that fluvial processes did not transport the bones and rocks; and

— we studied sites where flood events left bone material redistributed. At those sites, moving water sorted the bones by density and size. This wasn’t the case at the Cerutti Mastodon Site, where everything from small molar fragments to large rocks were distributed, unsorted, around the site.

Regarding any argument that the bone breakage observed at the Cerutti site may have been caused by animal gnawing or other behaviors:

— No Pleistocene carnivore was capable of breaking a fresh mastodon femur at mid-shaft or producing the observed wide impact notch;

— The presence of attached and detached cone flakes is indicative of hammerstone percussion, not carnivoran gnawing, and there is no carnivore bone modification at the Cerutti Mastodon Site nor bone surface modification from gnawing; 

— The differential preservation of fragile ribs and vertebrae rather than heavy limb bones argues against trampling (also no telltale trampling markings) and is consistent with selective breakage by humans; and

—  Other skeletons of extinct mammals found in the same layer/strata were found relatively intact.

Regarding the conclusion that there is evidence of human activity at the site:

 — The distribution pattern of bones – they were not distributed across the site in a homogenous fashion, but were instead concentrated in two key areas;

— [Again,] the pattern of differential breakage – more fragile bones were intact while the heaviest/strongest were broken;

—  The pattern of breakage itself — spiral fractures indicated breakage of the bones when fresh. Impact notches and cone flakes indicated breakage from percussion;

— The way in which the rocks were broken — pieces of broken rock were found scattered throughout the site, in many cases far away from the rock they came from; and several pieces could be refitted, indicating how and exactly where particular stones broke;

— There were two main areas of concentrated bones and rocks;

— [What appeared to be] purposeful placement of some objects — mastodon femoral heads placed together side by side and the tusk driven vertically into lower sedimentary layers were two examples of these anomalies; and

— [Again,] the discrepancy between how the fossils were preserved compared to other Ice Age megafauna discovered at the same site – a sloth, a camel, an ancient horse, a dire wolf, and a capybara — which were the same age. These other animals were mostly the entire carcass/fully articulated skeletons; the mastodon was much more incomplete, and remaining bones were disarticulated and broken.***

Finally, Fullagar, upon examining the purported stone tools from the site, is convinced that the subject stones were actually used as tools. Without knowing the age of the site and their apparent association with the mastodon bones, Fullagar examined key sample stones as submitted by the site archaeologists for study. “Initially when we looked at them I was thinking perhaps they were some kind of plant processing or animal processing tool, for grinding up plant materials or small animals,” said Fullagar. “We’re able to look at these [stones] in low and high magnification and also check whether or not we can see marks that are distinctive of a stone on a bone or a stone on stone.”  He found markings indicating stone on bone.  “It turned out after I knew a bit more about the site [after examining the bones] that they were used for smashing up mastodon bones,” said Fullagar.  

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Unbroken mastodon ribs and vertebrae, including one vertebra with a large well preserved neural spine. Courtesy San Diego Natural History Museum

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A view of a unit containing several fossil remains and stones. Courtesy San Diego Natural History Museum 

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A close-up view of a spirally fractured mastodon femur bone. Courtesy Tom Deméré, San Diego Natural History Museum 

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The surface of mastodon bone showing half impact notch on a segment of femur. Courtesy Tom Deméré, San Diego Natural History Museum 

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Side view of groove produced by percussion on a mastodon leg bone. Shows negative flake scar. Courtesy Tom Deméré, San Diego Natural History Museum 

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A boulder discovered at the Cerutti Mastodon site thought to have been used by early humans as a hammerstone. Courtesy Tom Deméré, San Diego Natural History Museum 

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One of the stones discovered at the Cerutti Mastodon site thought to be used as an anvil for bones processing. Courtesy Tom Deméré, San Diego Natural History Museum 

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Layout depicting bone breakage experiment on a modern elephant’s leg bones in an attempt to determine the kinds of breakage patterns resulting from hammerstone percussion. Courtesy Kate Johnson, San Diego Natural History Museum 

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What kind of human?

There were no human remains found at the site associated with the finds. But even if it could be irrefutably concluded that humans were at the site 130,000 years ago, what kind of human would we be talking about in this case? At that time in prehistory scientists know that, along with modern humans, other hominins like Homo erectus, Neanderthals, Denisovans, and possibly Homo floresiensis (the Indonesian “hobbits’) were walking the earth, and perhaps at least one other as yet unidentified early human species. However, all of these human populations are known to have existed only in the Old World. There is at this time no evidence that any species of human had journeyed beyond the Old World continents any earlier than between 20,000 – 30,000 years ago, a time when there are clues that humans may have been hanging around the ancient Beringian region (which includes present day Alaska and ancient easterly extensions of present day Siberia). And while it is possible they may have been modern humans (not archaic humans), there is no broadly accepted evidence to date that modern humans had left Africa to colonize the world by 130,000 years ago. Most estimates place them exiting Africa much later. 

This leaves hominins like Homo erectus, the first generally recognized globe-trotting human species, Neanderthals (known to have existed in Western Eurasia and the Middle East and as far east as the Altai Mountains in Siberia), Denisovans (known to have existed as far east as Siberia and possibly Melanesia and Australia), Homo floresiensis (Indonesia), or some other unknown species.  Any of those possibilities would be game-changing. Especially given the geographic realities of the time………

If a human presence is confirmed, then how did they get here?

The age range of the site falls within the Eemian interglacial period, a time when sea level was high enough to create a water barrier for theorists who posit that early humans crossed Beringia, the land bridge area that many scholars suggest facilitated the entry of humans into the Americas during prehistoric times. This would suggest that early human arrivals in the Americas would have had to reach the Americas by some kind of watercraft — or that their ancestors crossed into the Americas considerably earlier than 130,000 years ago, when sea level was lower and Beringia was above water. Either scenario would be considered by mainstream conservative thinkers to be a real stretch. 

But there are some findings in other parts of the world that suggest that humans were capable of crossing significant bodies of water in deep prehistory with boats of some sort. The evidence is indirect, but they present a compelling possibility. One example, on the Cycladic island of Naxos, Greece, could hold a clue.

First discovered in 1981 as part of a survey by the École Française d’Athènes under the direction of René Treuil, the site, known as Stélida, is a 118m high hill on the west of cape of Aghios Prokopios, located on the northwest coast of Naxos. Today the hill is situated on a promontory that juts out into the Aegean, and if one stands at its pinnacle, one can view a vista of the coastline and the Aegean Sea toward the west, separating Naxos from its neighboring island, Paros, clearly seen in the distance. Beginning in 2013, an international team led by Dr. Tristan Carter of McMaster University through the Canadian Institute in Greece, and his co-director Dr. Demetris Athanasoulis of the Cycladic Ephorate of Antiquities of the Hellenic Republic’s Ministry of Culture and Sports, conducted a series of ongoing excavations on the hill. Known as the Stélida Naxos Archaeological Project (SNAP), excavations have uncovered thousands of lithic material (mostly stone debitage), that indicate the site was in use for tens of thousands of years as a place to acquire and manufacture simple stone tools. According to the project scientists, many of the diagnostic pieces, although not an indicator for direct or absolute dating, do suggest a possible date range of hominin occupation or use going back as far as the Middle Paleolithic (spanning from 300,000 to 30,000 years ago). Says Kate Leonard, an archaeologist who worked at the site, “There is tantalizing evidence for activity at Stélida in the form of possible bifaces that could be interpreted as handaxes; these large heavy tools could have been made by Homo heidelbergensis, the predecessor of the Neanderthals in Europe. The possibility for evidence of these early hominids living on what are now the Cycladic islands has not been seriously investigated before.” 

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Stone tools in situ at Stélida. Photo credit Kate Leonard  

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Perhaps the most intriguing aspect of Stélida, however, is its location on an island that, during the Middle Paleolithic, would have presented some challenge for access by humans. “Stélida is the earliest known archaeological site in the Cycladic region and when the area was first reached by hominins the landscape would have been much different to now,” says Leonard. “When I looked out from my excavation trench towards the coast I could see the Aegean Sea separating Naxos from its neighbor to the west, the island of Paros. Scientific investigations into the ancient environment suggest that these two islands were joined to a few others as part of one big island known as the ‘Cycladean Island’ during the glacial maximum (the stage of the Ice Age when the maximum amount of sea water was trapped in glaciers). Tens of thousands of years ago when people climbed the hill at Stélida to reach the chert outcrops they would have been looking out over a grassy plain, an estuary or even a lagoon, with the sea many kilometers away. But even still, this ‘mega-island’ was an island and a body of water had to be crossed to reach it from mainland Europe.” Early humans were already known to have existed in mainland Europe at this time, such as Neanderthals, Homo heidelbergensis, and possibly Denisovans.

The clues don’t stop with Stélida. Another site called Mochlos on the island of Crete has revealed stone tools that may be as much as 130,000 years old. The Mochlos site had to have been reached by humans by crossing water, as it was never connected to the Greek mainland. And yet other sites in the south of Spain show evidence of human activity or presence as much as 900,000 to over a million years ago at locations that suggest early humans had to have crossed the Straits of Gibraltar from northern Africa to reach the sites.  

Looking ahead — the need for more sites? 

So does the Cerutti Mastodon Site show plausible evidence that humans were at the site 130,000 years ago? 

Broad scholarly consensus on that question is for now only a fiction. Human bones would certainly cement the case, but there are no telltale early human bones, and that is not unusual. Many prehistoric sites showing clear evidence of human activity do not feature human bones. But DNA research has opened up an intriguing possibility for investigating such sites. Using newly developed techniques, researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have recently successfully retrieved and identified DNA from Neanderthals from sediment samples taken from four archaeological cave sites, as well as DNA of Denisovans from soil samples from the Denisova Cave in Russia. The DNA was identified in sediments where no hominin skeletal remains have been detected. Scientists now suggest that the same process can be applied at other sites across the world. Why not the Cerutti site? 

Aside from breakthroughs like new DNA techniques, Deméré and colleagues hold out for more research and study before cementing their case. They suggest that, now that the Cerutti site has opened up a new possible time range for human occupation in the Americas, it may serve to inspire or direct other researchers or archaeologists to search in areas and sediments/time horizons that were previously ignored or not thoroughly explored. More data and possible evidence from other locations is needed before the Cerutti site can be corroborated within the scholarly world. They are moving forward with this. For starters, says Steven Holen, “we have some preliminary evidence from another site,” that will be explored further.  

He wouldn’t reveal the location of the site. Not yet. 

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A drawer full of Cerutti Mastodon site stone artifacts in the San Diego Natural History Museum’s Paleontology Collection Room. Courtesy Kate Johnson, San Diego Natural History Museum 

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*Interview on Science Friday, April 2017

** CMS Discovery Timeline, San Diego Natural History Museum

***CMS Fact Sheet, San Diego Natural History Museum

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The Girl in the Cave

By James Kensington

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Tulum, Quintana Roo, in the Yucatán Peninsula of Mexico — It was in May of 2007 when the divers approached it—a cenote deep inside the jungle. Cenotes, or water-filled sinkholes, are not uncommon in these parts. In fact, in the Yucatán, they exist by the thousands. Divers and archaeologists alike love them for the secrets they hide — secrets that could reveal much about a past human presence in a subtropical world that seemed to serve as an unlikely setting for one of the greatest of ancient civilizations, the Maya. Alberto Nava, who took the lead on this dive, is something of a veteran when it comes to such ventures. He is a professional diver with the Bay Area Underwater Explorers, a California-based nonprofit organization dedicated to exploration and conservation of the world’s underwater regions. With his two other diving companions, Alex Alvarez and Franco Attolini, he plunged into the cenote, an entry into an elaborate underwater cave system known as the Sac Actun. It was not unlike most any other dive — until they encountered an unexpected drop.

“We traveled through a flooded tunnel for about 1 mile before we reached the edge of this pit,” recounts Nava. “The floor disappeared under us, and we could not see across to the other side. We pointed our lights down and to the sides. All we could see was darkness. We felt as if our powerful underwater lights were being absorbed by this void, so we called it Black Hole, which in Spanish is Hoyo Negro.”

Nava and his colleagues could see that there was much more to this than they could absorb on a first dive. So they waited for another day.

“A couple of months later, we ventured deeper into this darkness and reached the floor of the pit at about 170 feet. It was a bell-shaped structure 200 feet in diameter. The center was littered with large boulders stacked on top of each other. As our eyes got accustomed to the environment, we started to notice large animal bones. The first one we found was a 3- foot-long femur resting against one of the boulders. My teammates started signaling in all directions as they pointed to animal remains that were resting at the bottom and on the walls of the pit. At that time, we were not sure what kind of bones we were looking at, but we knew they were old and big. All of the sudden, Alex pointed to a human skull resting on the top of a small ledge. It was a small cranium laying upside down with a perfect set of teeth and dark eye sockets looking back at us. The skull was resting on its humerus, and we could see the rest of the upper torso spread to the left and down on the ledge.”

As they usually did when encountering new finds, they began documenting the site. But they could see that this was a discovery that required more specialized attention.

“In 2009, we reported the site to archaeologist Pilar Luna from Mexico’s National Institute of Anthropology and History (INAH), and together we created the Hoyo Negro Consortium (www.hoyonegro.org ), a group of cave divers and researchers working to unravel the mysteries of Hoyo Negro.”

With this, the real scientific journey began at full throttle.

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A broad view of Hoyo Negro, shot from the floor near the south edge, showing the immensity of the chamber and the complexity of the boulder-strewn bottom. One access tunnel can be seen near the ceiling at top left. This photo was taken by the “painting with light” method on a 30 second exposure. Text and photo credit: Roberto Chavez Arce

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The skull as it was discovered in 2007, resting against the left humerus (upper arm bone).
Photo and text credit: Daniel Riordan Araujo

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The skull as it appeared in December 2011, after rolling into a near-upright position.
Photo credit: Roberto Chavez Arce

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The Cave and The Water Nymph

Under the auspices of the new consortium, the task now fell to an international interdisciplinary team of scientist-specialists to undertake the meticulous job of additional recording, recovery, examination, and analysis of the various finds — finds that would eventually lead to some headline-making conclusions.

For the anthropologists and archaeologists of the group, the greatest excitement naturally focused on the human remains, what was turning out to be a nearly complete skeleton. But before anyone could understand the age and significance of the skeleton, they needed to understand the context. This required the efforts of specialists with knowledge of things like geology and cave formation, paleontology, dating techniques, and genetics. 

Patricia Beddows of Northwestern University is one of those specialists. Her work has focused on cave systems formed by the dissolution of soluble carbonate rocks like limestone and dolomite, especially the flooded caves of the Yucatán Peninsula, including Hoyo Negro. She has logged countless hours diving into the cave systems. “Research in flooded caves is much like space exploration, with divers similar to astronauts reporting back to ‘mission control’ — a much larger scientific team at the surface,” said Beddows. “It all has to be done on SCUBA, which is our life support system.” Beddows’ studies have shown how the extensive Yucatán cave system has drained groundwater to the coast and how the water level in the caves has closely matched the sea level changes over time. “Using this knowledge, we understand how Hoyo Negro has changed over thousands of years,” she says. This has helped to date Hoyo Negro, once a drier cave chamber with lower water levels, to more than 12,000 years ago, when many of the bones or animals, including the human, had apparently fallen into or entered the cave. Her work with the re-crystalized rock sediments in the cave system also helped. The rocks and the bones in Hoyo Negro are coated with rock crystals, including a new form of crystal that Beddows calls “florets”. Using Uranium/Thorium dating analysis, scientists have been able to accurately and reliably date the bone. “An impressive aspect of this research is that we have dated the skeleton directly, but we also have supported these dates with additional dates on the florets,” Beddows said.

But narrowing down the dating has been very much a team effort, with a multi-pronged approach. To begin with, the cave-diving scientists knew that the human skeleton was found within the context of the skeletal remains of 26 large mammals, many of which were identified as the bones of long-extinct fauna, such as saber-toothed cats and gomphotheres (extinct relatives of mastodons). These are mammals that lived more than 11,000 years ago. The human skeleton was found near the bones of a gomphothere. Douglas Kennett, professor of environmental archaeology at Penn State, and Brendan J. Culleton, postdoctoral fellow in anthropology at Penn State, worked with colleagues to construct a geochronological framework for the skeleton by using a combination of methodologies that successfully constrained the age to the end of the Ice Age, the Late Pleistocene. Working with Yemane Asmerom and Victor Polyak from the University of New Mexico, they applied global sea level rise data to determine when the cave system filled with water. As the bones now lie about 130 feet below sea level, they estimated that sea level rise would have raised the groundwater level in the cave system and submerged the bones between 9,700 and 10,200 years ago. Thus, the latest animals and humans could have entered the cave system in a dry state was about 9,700 years ago.

In addition, enamel extracted from a tooth of the skeleton was radiocarbon dated to 12,900 years ago by Kennett’s lab.

“Unfortunately, we can’t rule out that the tooth enamel is contaminated with secondary carbonates from the cave system, but we removed potential contaminates using standard techniques and Tom Stafford, Stafford Research Laboratories, produced a comparable age,” said Kennett. “We consider this a maximum age and when combined with the uranium thorium dates from the adhering speleothems, we argue that the skeleton dates between 12,000 and 13,000 years ago. Well placed as a Paleoamerican.”

A Paleoamerican. This was something quite different than an ancient Mayan. The Maya, best known for the iconic monumental Mesoamerican cities like Chichen Itza, Tikal, and Copan, lived and dominated Central America from about 2000 B.C to about 1500 A.D. The Paleoamericans lived thousands of years earlier, inhabiting the American continents during the final glacial episodes of the late Pleistocene period, as far back as 15,000 years ago. The bones of this skeleton were dated to between 12,000 and 13,000 years ago. This represented one of the six oldest humans found in America. And it was certainly the most complete find for that time period. 

But there was more to the skeleton than age. After examination, the team determined that the skeleton belonged to a slightly-built, 4-foot-10-inch girl of between 15 and 16 years of age. A teenager. She may have fallen into the pit while searching for water more than 12,000 years ago, the team surmised. A plausible scenario, as there was no evidence that she had been attacked, killed and dragged into the cave chamber by another preying animal. Scientific teams like to give nick-names to their biggest finds, especially if they are human skeletons. So the Hoyo Negro team called this one Naia, a greek reference to a water nymph. The name stuck and, along with names like “Lucy”, “Turkana Boy” and “Kennewick Man”, “Naia” was soon becoming something of a household word among scientists and the public, alike.

More important to the scientists, however, was that her features were consistent with those often attributed to Paleoamericans based on previous excavations and studies. “The earliest human skeletons found in the Americas differ markedly from those of modern Native Americans in the shapes of their skulls, faces and teeth,” said Dr. James C. Chatters of Applied Paleoscience, lead author of a recently published study related to the Hoyo Negro finds. The 9,000+-year-old Kennewick Man, found near Kennewick in Washington State in 1996, and also examined by Chatters, was a prime example.

Deciphering the ancestry of the first people to populate the Americas has been a challenge. On the basis of some genetic studies, modern Native Americans are thought to descend from Siberians who moved into eastern Beringia (the landmass that anciently connected Asia and North America) between 26,000 and 18,000 years ago. These people, considered the earliest Americans, are suggested to have then spread southward and populated the rest of the continent. But despite widespread support for this idea, the ancestry of the earliest Americans is still debated because, among other things, the facial features of the oldest American skeletons don’t look much like those of modern Native Americans. Thus, in terms of the Native American origins debate, the Hoyo Negro story is significant. And to this, the genetics contingent of the team had something to say about Naia………….

Haplogroups and Beringia

As is often the case, interdisciplinary scientific teams often turn to the best technical experts when it comes to finding answers to their questions. So it was that the Consortium approached Applied Paleoscience founder and Director James Chatters, a forensic anthropologist, archaeologist, and paleontologist. It was Chatters who played the lead role in the study of the famous Kennewick Man, and it is Chatters who is now leading the examination and analysis of Naia’s remains, resulting in a recently-published study that has catapulted Naia front-and-center on the stage of Native American origins research. 

For the genetic examination component, Chatters recruited Brian Kemp of Washington State University to take the lead. Using the latest techniques, Kemp, a molecular anthropologist with expertise in the field of ancient human genetics, has sequenced DNA from ancient human remains found in both North and South America, including human coprolites — ancient excrement — from archaeological sites in Oregon and the American Southwest. His task was to tease out small amounts of Mitochodrial DNA (mtDNA), found in the energy-generating structures of cells, of one of Naia’s teeth. Isolating and sequencing mtDNA is common among studies of ancient human remains, as organisms contain many more copies of it than chromosomal DNA. And because it is inherited from the mother, one can determine maternal ancestry.

Extracting and analyzing Naia’s DNA was challenging, to say the least. “There is very little DNA preserved in a skeleton of such great antiquity,” said Kemp.

But because mtDNA is so much more plentiful than chromosomal DNA, and because scientists have now clocked years of experience sequencing mtDNA from ancient bones, it was a feasible undertaking. Using molecular biological techniques to amplify the DNA, Kemp was able to make hundreds of billions of copies of Naia’s original DNA material. “Once so many copies are made,” said Kemp, “it is pretty straightforward to study the DNA.”

The study results were enlightening. Kemp had determined that Naia shared a common ancestry with many of today’s Native Americans — a genetic signature that is derived from an Asian lineage but is only found in the Americas today. Called Haplogroup D1, it is found throughout North, Central and South America. It is thought that about 11% of Native Americans exhibit this haplogroup — especially in South America, where it shows up in about 29% of indigenous Chileans and Argentinians. Geneticists theorize that this lineage arose in Beringia after the ancient Beringian population separated from other Asian populations.

Kemp then asked two other expert colleagues to conduct similar tests on Naia’s tooth to verify his results. Deborah Bolnick, assistant professor of anthropology at the University of Texas at Austin, came up with essentially the same results. University of Illinois anthropology and Institute for Genomic Biology professor Ripan Malhi, focusing on regions of the mitogenome that mutate more slowly than other parts of the genome (and thus could be more reliable markers of genetic relatedness through time), also corroberated Kemp’s results. 

Three separate labs had confirmed the same results. Naia, a Paleoamerican with physical characteristics distinctly different than today’s Native Americans, shared the same ancestry — an ancestry that pointed to ancient Beringia — and by extension to Asia.

The finding was not altogether startling. Previous studies have indicated similar results. But this is the first time that a nearly complete skeleton of this age has been genetically linked to today’s Native Americans, and protractively to Beringia and Asia. “Because she exhibits distinctive Paleoamerican skull and facial features,” says Bolnick, “the study shows for the first time that Paleoamericans with these distinctive features can have Beringia ancestry.”

Yet, what accounts for these different physical characteristics?

It could be evolution, suggests Bolnick and colleagues. “It seems likely that differences between Paleoamericans and Native Americans of today are due to evolutionary changes that occurred in Beringia and the Americas over the last 9,000 years,” she says. To support her suggestion, Bolnick points to evolutionary changes that have occurred over the last 10,000 years in other populations — a comparatively short time period on the evolutionary time scale, traditionally measured in millions of years. “There have also been studies of the skeletal morphology in later remains discovered in the Americas over the last 10,000 years. We certainly do see changes in the skull shape, in the facial features over that period of time.”  She points additionally to Native American populations in South America who live at high altitudes, who evolved genetic and physical characteristics that have facilitated their survival in these regions.

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The upper right third molar of Naia, which was used for both radiocarbon dating and DNA extraction. The tooth is held by ancient genetics expert Brian Kemp of Washington State University, who led the genetic research on the skeleton. Photo credit: James Chatters

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The 10,000-Year Homeland

The Naia story and its evolutionary element have important implications in connection with other recent studies related to Native American origins. Some of them revolve around one emerging theory that has drawn the focus and attention of researchers from all over the world. Known as the “Beringia Standstill” theory, it was first suggested by two Latin American geneticists in 1997 and then refined or corroborated by a University of Tartu research team in Estonia in 2007. From a sampling of mitrochondrial DNA from more than 600 Native Americans, they found that mutations in the DNA pointed to the likelihood that a group of their direct ancestors from Siberia was isolated from their Siberian origins for at least several thousand years, during the time period from 25,000 (if not earlier) to 15,000 years ago (when ice-free corridors developed), before their descendants moved into the Americas. Evidence from recent paleo-ecological research suggested that this isolation most likely occurred in Beringia, a land mass that once covered the present-day Bering Strait between northeast Asia and Alaska. 

“A number of supporting pieces have fallen in place during the last decade, including new evidence that central Beringia supported a shrub-tundra region with some trees during the last glacial maximum and was characterized by surprisingly mild temperatures, given the high latitude,” said John Hoffecker of CU-Boulder’s Institute of Arctic and Alpine Research, who is the lead author of a related Perspective article that appeared in the Feb. 28 issue of Science magazine. 

This is an important aspect within the overall geographic context of the area, as the last glacial maximum reached its peak about 21,000 years ago with the development of massive ice sheets across North America and Europe, essentially blocking access to North America from northeast Asia until about 15,000 years ago. Thus the ice sheet barrier, along with distance from Siberia, would have created a geographic basis for the gap suggested by the genetic data.

But combining the genetics with the recent paleoecological research, which involved analyzing fossil pollen, plant and insect material taken from sample sediment cores from the now submerged landscape, has been the key.

“The genetic record has been very clear for several years that the Native American genome must have arisen in an isolated population at least by 25,000 years ago, and the bulk of the migrants to the Americas really didn’t arrive south of the ice sheets until nearly 15,000 years ago,” said co-author and University of Utah anthropologist Dennis O’Rourke. “The paleoecological data, which I think most geneticists have not been familiar with, indicate that Beringia was not a uniform environment, and there was a shrub-tundra region, or refugium, that likely provided habitats conducive to continuous human habitation.” 

Scott Elias, an article co-author and a professor with the Department of Geography at Royal Holloway, elaborated: “We believe that these ancestors survived on the shrub tundra of the Bering Land Bridge because this was the only region of the Arctic where any woody plants were growing. They needed the wood for fuel to make camp fires in this bitterly cold region of the world. They would have used dwarf shrub wood to get a small fire going, then placed large mammal bones on top of the fire, to ignite the fats inside the bones. Once burning, large leg bones of ice-age mammals would have burned for hours, keeping people alive through Arctic winter nights.”

On the genetic side of things, the theory that humans inhabited Beringia for as much as 10,000 years “helps explain how a Native American genome (genetic blueprint) became separate from its Asian ancestor,” said O’Rourke.

“At some point, the genetic blueprint that defines Native American populations had to become distinct from that Asian ancestry,” he explains. “The only way to do that was for the population to be isolated. Most of us don’t believe that isolation took place in Siberia because we don’t see a place where a population could be sufficiently isolated. It would always have been in contact with other Asian groups on its periphery.”

“But if there were these shrub-tundra refugia in central Beringia, that [would have] provided a place where isolation could occur” due to distance from Siberia, O’Rourke says.

In contrast to the genetic and paleoenvironmental evidence, however, the archaeological record has been lacking. This would be explained by the suggestion that, according to a number of scholars, the archaeological evidence was submerged under the rising sea levels that resulted in today’s geography of the region. “These shrub-tundra areas were likely refugia for a population that would be invisible archaeologically, since the former Beringian lowlands are now submerged,” maintains O’Rourke. The suggestion that rising sea levels subsequently covered the evidence of human migration into the Americas has also been a long-standing theory among researchers studying the model that advances the notion that early Native Americans moved south along the Pacific coast as the glaciers receded and sea levels rose. 

In addition, Hoffecker suggests that the Beringia inhabitants during the last glacial maximum could have made successful hunting forays into the uninhabited steppe-tundra region to both the east and west of central Beringia, where drier conditions and more grass supported a plentiful array of large grazing animals, including steppe bison, horse and mammoth.

There is now solid evidence for humans in Beringia before the last glacial maximum, as geneticists first predicted in 1997, according to Hoffecker. After the maximum, there are two sets of archaeological remains dating to less than 15,000 years ago. “One represents a late migration from Asia into Alaska at that time,” he said. “The other has no obvious source outside Beringia and may represent the people who are thought to have sheltered on the land bridge during the glacial maximum. If we are looking for a place to put all of these people during the last glacial maximum, Beringia may be the only realistic option.”

Hoffecker, O’Rourke and colleagues say new archaeological sites must be found in Beringia if the long human layover there is to be confirmed. Although most such sites are presumed to be underwater, they are hopeful that some evidence of human habitation in shrub-tundra areas might remain above sea level in low-lying portions of Alaska and eastern Chukotka (in Russia).

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Map of ancient Beringia, showing the outlines of modern Siberia (left) and Alaska (right) with dashed lines. The area in dark green is the portion of Beringia (now submerged by the ocean) near the end of the last glacial maximum, a period that lasted from 28,000 to 18,000 years ago when sea levels were low and ice sheets extended south into what is now the northern part of the lower 48 states. Photo Credit: Wlliam Manley, Institute of Arctic and Alpine Research, University of Colorado. Illustration below: credit Julie McMahon

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Moving Forward

Although the Hoyo Negro findings have added significant additional support for the Beringian origins theory, the scientists caution that there is much more work to do before any far-reaching conclusions can be drawn. After all, Naia has shown that she is related to only 11 percent of all Native Americans. What about the other 89 percent? The findings thus far suggest that at least some modern-day Native Americans can trace their roots to an ancient Beringian population. But scientists have learned, over and over again, that the more they discover about human prehistory, the more they realize they don’t know. Reconstructing the past often turns out to be far more complicated than we initially suppose. And this, the Hoyo Negro scientists would likely agree, makes the whole journey of discovery all the more exciting.

“The dating and genetic analysis of Naia is a first step in what we hope will be a long productive investigation of Hoyo Negro,” says Chatters, looking ahead. “Our next steps will focus on attempting to sequence Naia’s nuclear DNA, determining the ages and genetics of the cave’s other animal skeletons and reconstructing the environment in which they and Naia lived.”

But it will all take a village of experts, just as it has to this point, employing a variety of disciplines and skills to re-create the evolving picture. “Balancing all of these elements has been a wonderful challenge,” says Pilar Luna from INAH. “On the one hand, we have a large team of renowned scientists who have been extremely generous sharing their knowledge and experience to analyze, understand, and interpret the findings, in order to produce the knowledge we have gotten so far. On the other hand, there are the cave divers, who have taken specialized courses to gather data for archaeological purposes, to properly record the general context taking samples, measurements, photos, videos, etc., and following with extreme care all requests made by the experts, in spite of the complexities and dangers of the cave itself. Also, we have had the support from engineers and technicians who have developed extraordinary methods to be used in this project for the first time, with significant results, mainly in the fields of software and photography.”

The combined efforts will extend to protecting the cave itself from would-be looters and other environmental dangers, so that research can continue as long as possible. “We feel obligated to protect this incredible resource,” says Nava. “So we are working with INAH and other Mexican authorities to control site access and make sure Hoyo Negro is preserved for future generations.”

Time will tell the ultimate fate of the Black Hole. In the meantime, what is collected of Naia’s remains will rest enshrined within laboratory walls and, perhaps in time, behind museum glass. 

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 Article Supplement

Naia’s World of Gomphotheres

When University of Arizona archaeologist Vance Holliday and colleagues began uncovering large fossilized bones at the site of El Fin del Mundo in the Sonoran Desert of northwestern Mexico in 2007, they weren’t sure what kind of animal they were unearthing. 

“At first, just based on the size of the bone, we thought maybe it was a bison, because the extinct bison were a little bigger than our modern bison,” said Holliday, who has been researching geoarchaeology at Paleoindian sites across the U.S. for years.

Then, in 2008, they discovered something that clinched it for them.

“We finally found the mandible, and that’s what told the tale,” Holliday said.

It was a gomphothere.

Actually, two of them.

About the same size as a modern elephant, but smaller than their extinct cousins the mammoths, gomphotheres were once widespread in North America but were thought to have disappeared from the fossil record long before humans arrived in North America some 13,000 to 13,500 years ago.

Until now.

Radiocarbon dating of charcoal flecks and burned bone found within the context of the fossils indicated a reliable age of 13,390 years. This made these two gomphotheres the last known gomphotheres in North America.

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Gomphothere mandible in place, upside down, at El Fin del Mundo excavation site. The fossil was fully prepared at the INAH zooarchaeology lab in Mexico City. Image courtesy of Vance T. Holliday.

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The fully excavated and prepared gomphothere mandible. Courtesy Joaquin Arroyo-Cabrales/Instituto Nacional de Antropología e Historia

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These sculptures, made by Mexican artist Sergio de la Rosa, show three elephant ancestors: (from left to right) the mastodon, the mammoth and the gomphothere. Courtesy Sergio de la Rosa

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But there was more.

As they excavated among the bones, they also uncovered human artifacts—Clovis artifacts, to be specific—including 7 projectile points, some stone cutting tools and 21 flint flakes from stone tool-making. The position and proximity of the Clovis fragments relative to the gomphothere bones at the site suggested that humans did in fact kill the two animals there. Of the seven points found at the site, four were in place among the bones, including one with bone and teeth fragments above and below. The other three points had eroded away from the bone bed and were found scattered nearby. This suggested that the gomphotheres were likely hunted and thus constituted a Clovis prey species, along with mammoths, mastodons, and bison, already known to have been hunted by the Clovis.

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A clear quartz Clovis point found near the bone bed at El Fin del Mundo. Although very difficult to shape into a tool, quartz was used by Clovis tool makers at several sites.  Courtesy INAH Sonora.

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“This is the first Clovis gomphothere, it’s the first archaeological gomphothere found in North America, it’s the first evidence that people were hunting gomphotheres in North America, and it adds another item to the Clovis menu,” Holliday said.

The Clovis culture, today considered the oldest clearly defined and recognized Paleoindian culture in the Americas, is characterized by its distinctive stone tools, particularly the fluted projectile points. The first examples of this culture were discovered by archaeologists near Clovis, New Mexico, in the 1930s. The El Fin del Mundo site, along with the Aubrey site in Texas, is now among two sites that show the earliest solid evidence of Clovis hunting in North America, indicating that the earliest widespread and recognizable group of hunter-gatherers were already in place 13,390 years ago in the North American Southwest.

Holliday and colleagues suggest that the finds support the model of an American southwestern origin for the Clovis material culture. As they conclude in the study, published this week in the Proceedings of the National Academy of Sciences:

“These data expand our understanding of the age range for Clovis, Clovis diet, raw material preference, and the late Pleistocene megafaunal assemblage of North America, and provide evidence for a southern origin of the Clovis technocomplex.”*

Holliday and the study team report that the radiocarbon ages from El Fin del Mundo were made based on testing the site’s charcoal, shell, and organic matter at the Arizona Accelerator Mass Spectrometry Laboratory.

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*Article #14-04546: “Human (Clovis)–gomphothere (Cuvieronius sp.) association ~13,390 calibrated yBP in Sonora, Mexico,” by Vance T. Holliday et al.

In addition to Holliday, authors of the PNAS paper include: lead author Guadalupe Sanchez, who has a doctorate in anthropology from the UA; UA alumni Edmund P. Gaines and Susan M. Mentzer; UA doctoral candidates Natalia Martínez-Tagüeña and Andrew Kowler; UA master’s student Ismael Sanchez-Morales; UA scientists Todd Lange and Gregory Hodgins; and Joaquin Arroyo-Cabrales at the Instituto Nacional de Antropología e Historia.

The dig at El Fin del Mundo, a joint effort between the U.S. and Mexico, was funded by the UA School of Anthropology’s Argonaut Archaeological Research Fund, the National Geographic Society, the Instituto Nacional de Antropología e Historia and The Center for Desert Archaeology in Tucson.

Source: Some material for this article was adapted and edited from a University of Arizona press release, Meet the gomphothere: UA archaeologist involved in discovery of bones of elephant ancestor

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Spirit Cave

By Jesse Holth

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In 1940, archaeologists Georgia and Sydney Wheeler were working for the Nevada State Parks Commission, surveying for sites that were damaged by looting and guano mining. The couple, performing salvage excavations in the Great Basin Desert, noticed a cave and discovered a short passage inside, leading to a small chamber. Creating a test pit along the chamber’s back wall, Georgia uncovered two sets of human remains, stacked on top of each other. The first burial was one foot deep, wrapped with a fragment of finely woven (twined) tule or cat-tail. Beneath it, she found the second burial at a depth of 2.3 feet.

Working on Burial 2, the Wheelers noted in their journal: “Upper portion of body is partially mummified. Leather mocassins [sic] on the feet. Scalp and some hair on the head. The hair was black when uncovered but rapidly changed to reddish on exposure to the light and air. Body was laid on a fur blanket. Finely woven twined mat of tule or cat-tail was wrapped around upper portion and stitched to form a bag over the head. A second similar mat was wrapped around the lower portion. The mats overlapped. An open twined mat was placed over the whole bundle and the lower corners tied together under the feet.”

It was a remarkable find.

The Wheelers named the site Spirit Cave, and the second, better preserved burial became known as the “Spirit Cave Mummy”. That summer, the remains were displayed at the Nevada State Fair in Fallon before being moved to the Nevada State Museum, where they remained for fifty years. It wasn’t until the 1990s that the significance of this find would be revealed: originally thought to be only 1,500–2,000 years old, radiocarbon testing between 1994 and 1996 dated the remains to 10,500 years old. The Wheelers had discovered remains that were preserved less than a meter below the surface for a shocking ten millennia.

The 1990s also saw the introduction of new legislation regarding ancient remains: NAGPRA, the Native American Graves Protection and Repatriation Act. The Fallon Paiute-Shoshone Tribe made a NAGPRA claim in 1997, stating cultural affiliation with the remains from Spirit Cave. But it wasn’t until recently that DNA evidence proved this affiliation – long after requests to repatriate the remains were refused, mainly based on morphometric analysis of the cranium. This type of identification has since been debated, especially when it comes to NAGPRA claims. DNA analysis is much more accurate, rapidly becoming the ‘gold standard’ for assessing relationships between individuals and populations.

Studies from 1997 indicated that the Spirit Cave Mummy was a male between the ages of 40 and 50, with traces of osteoarthritis in his joints and an extra thoracic vertebra (13 rather than 12). There was a fracture to the frontal bone of his skull, which had completely healed, but three abscessed teeth which were likely the cause of death. His last meals were bulrush (Scirpus) seeds, and two species of fish, likely from the marshes near the cave.

Peopling the Americas: An Emerging New Picture

Although the Spirit Cave remains have been rightfully repatriated, this has not stopped the advancement of scientific inquiry. New research, conducted by Professor Eske Willerslev and colleagues, provides insight into the genetics of not only Spirit Cave, but other remains across North and South America. This includes the 10,400-year-old Lagoa Santa remains, found in Brazil in the 19th century. Together, DNA findings from these two sites contradict the earlier belief that they had belonged to a group of “Paleoamericans” pre-dating Native Americans. “Our study proves that Spirit Cave and Lagoa Santa were actually genetically closer to contemporary Native Americans than to any other ancient or contemporary group sequenced to date,” said Willerslev, who holds positions at both St. John’s College, University of Cambridge, and the University of Copenhagen.

The study involved sequencing 15 genomes from ancient specimens, six of which are over 10,000 years old, and spanned a geographic range from Alaska to Patagonia. Interestingly, all of the remains studied were most closely related to Native Americans, including two so-called “Paleoamericans” and an individual from Ancient Beringia. This challenges a previous theory that “Paleoamericans” were distinct from Native Americans because they had a different cranial form. Craniometry is a centuries-old method that increasingly seems to have very little bearing on modern archaeology and genetic identity. As Willerslev stated, “Looking at the bumps and shapes of a head does not help you understand the true genetic ancestry of a population.”

Specifically, research was conducted on the remains of four individuals from Lovelock Cave, Nevada; five individuals from Lagoa Santa, Brazil; an Incan mummy from Mendoza, Argentina; one individual each from Punta Santa Ana and Ayayema in Patagonian Chile; and remains from Trail Creek Cave 2 (Alaska), Big Bar Lake (British Columbia), and Spirit Cave (Nevada). Based on the DNA sequencing, researchers suggested an unsampled outgroup may have split from Native Americans around 24,700 years ago, overlapping with the inferred split of Native Americans from Siberians and East Asians at 26,100–23,900 years ago. While more data is required, this means that multiple splits occurred in Beringia within a short span of time, which could imply that a moderate population structure existed within Beringia. This supports a “Beringian standstill hypothesis”, as demonstrated by sites like Bluefish Caves.

The researchers estimated, based on their models of divergence, that the dispersal process in the Americas was considerably rapid – with populations expanding across North America in as little as centuries, and into eastern South America within a millennium or two. Data from Spirit Cave and Lagoa Santa showed that the dispersal pattern south of the continental ice sheets involved complex admixture events between earlier established populations. This is suggestive of multiple dispersals into South America. Moreover, the presence of the Australasian genomic signature in Brazil (at Lagoa Santa) indicates a population that reached South America but left no apparent traces in North America. Previous evidence for coastal dispersals could mean that the Australasian signal was brought to South America by a distinct seafaring population.

Geographic barriers like mountains often affect genetic signals, and the study revealed distinct ancestry in populations east of the Andes versus those on the western side. Isolation of gene pools can occur, causing a divergence in genetic signals. The study indicated that soon after arrival, South Americans diverged along multiple geographic paths, and that a second independent migration and gene flow occurred in the Middle to Late Holocene. Researchers also provided further evidence of isolation between groups of different populations in coastal British Columbia versus interior British Columbia (see “The Canadian Iceman”).

The Spirit Cave genome has strong genetic affinities to Lagoa Santa, but the Australasian signal was only detected in one of the Lagoa Santa individuals – the rest of these “Paleoamericans” had no Australasian signal. The Paleoamerican cranial form, therefore, is not associated with the Australasian genetic signal as previously suggested. This study demonstrated that divergences can be principally cultural, and that archaeological, anatomical, and genetic records are not necessary congruent. For example, Spirit Cave was originally thought to represent a genetically divergent group from Clovis, simply because the technologies found were different – but genetically close populations, in this case living on either side of the Rockies, can develop different cultural adaptations.

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Skulls and other human remains from P.W. Lund’s Collection from Lagoa Santa, Brazil. Kept in the Natural History Museum of Denmark. Natural History Museum of Denmark

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A skull from P.W. Lund’s Collection from Lagoa Santa, Brazil. Kept in the Natural History Museum of Denmark. Natural History Museum of Denmark

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Sumidouro Lake in Lagoa Santa, Brazil. The formation to the right of the picture contains the caves where the skulls were found. Natural History Museum of Denmark

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Diversity and Cultural Respect

Human dispersal and divergence in the Americas is still full of unanswered questions. Archaeologists are constantly discovering older sites and remains, pushing our dates back even further, and genetic discoveries are consistently complicating our view of the past. This study of Spirit Cave and other DNA sequences provided evidence that movement in the Americas was not simple, and not gradual – it entailed many different population groups, some still unknown, essentially “leap-frogging” across large landscapes. Some of these groups filled new environmental niches, and genetically drifted from ancestor populations due to isolation and geographic barriers.

It is important to remember, as we keep looking for answers, that there are still living descendants of some of these groups. NAGPRA provides some recourse for Native Americans looking for repatriation, but often it requires DNA evidence to demonstrate cultural affiliation. In the case of Spirit Cave, Professor Willerslev assured the Fallon Paiute-Shoshone Tribe that he “would not do the DNA testing unless they gave permission.” Once the remains were proven to belong to an ancestor, they were returned to the tribe and Willerslev attended the private reburial ceremony. He said, “it would be like if our father or mother was put in an exhibition,” noting that it was “deeply emotional and deeply cultural.” The tribe was involved throughout the process, and two members were present when all of the DNA sampling was done. Science and cultural sensitivity need not be at odds, as some have suggested: Spirit Cave and the Canadian Iceman are examples of how to be respectful as archaeologists, and that the overarching mandate should be to listen to living peoples about their ancestors.

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Professor Eske Willerslev with Donna and Joey, two members of the Fallon Paiute-Shoshone tribe. Linus Mørk, Magus Film

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