June 2011, Daily News

Early Humans Made Stone Handaxes Earlier Than Previously Thought, Study Says

By Dan McLerran   Wed, Aug 31, 2011

A major early human stone toolmaking industry has been pushed back in time as much as another 350,000 years, according to a recent study carried out by scientists at Columbia University and published this week in Nature. The discovery also revisits questions about the origins of an early human ancestor and the coexistence of disparate early human species in Africa.

Led by lead study author Christopher Lepre, a geologist who also has joint appointments at Rutgers and Lamont-Doherty universities, a joint French and American team explored, removed and dated samples of mudstone sediment deposits using magnetic polarity analysis from a site called Kokiselei, near the northwestern shores of Lake Turkana in Kenya. Magnetic polarity analysis, part of the process of Paleomagnetic dating, an absolute dating technique, is the evaluation of the shifts or reversals in the Earth's magnetic field through geologic time as it is reflected or "recorded" by changes in rocks and minerals found in volcanic and sedimentary deposits. The results of the analyses were converted to years to determine the age of the tested sediments.  

What they found was surprizing. Yielding a date of approximately 1.76 million years B.P.E., the targeted deposits were considerably older than they had anticipated. Moreover, these same sediments at Kokiselei contained stone tool assemblages identified with the Acheulian stone tool industry, an industry for which the oldest samples have been previously dated in Konso, Ethiopia, to about 1.4 million years ago, and in India, between 1.5 million and 1 million years ago. These tools, considered the second "great leap" in early human stone toolmaking, greatly expanded the possibilities for early humans, particularly in terms of food preparation and possibly even hunting. “You could whack away at a joint and dislodge the shoulder from the arm, leg or hip,” says Eric Delson, a Lehman College paleoanthropologist not involved in the study. “The tools allowed you to cut open and dismember an animal to eat it.” This utility implies a certain level of dexterity and the ability by the maker to think ahead, or plan. The most common and prolific example of such stone tools is the Acheulian Handaxe, found in abundance at sites across East Afrca as well as in Europe and Asia. 

The same sediments also contained stone tools of a simpler industry, the Oldowan, thought to be a predecessor to the Acheulian. The Oldowan is suggested by some scientists to be the handiwork of an early hominid called Homo habilis, the fossils of which were first discovered by Louis and Mary Leakey in the early 1960's and is thought to have lived from approximately 2.3 to 1.4 million years ago. But now, the new Kokiselei dating has pushed back the advent of the Acheulian industry by about 350,000 years.

Said Lepre, “We suspected that Kokiselei was a rather old site, but I was taken aback when I realized that the geological data indicated it was the oldest Acheulian site in the world.” 

Homo erectus the maker?

The Acheulian is most often associated with Homo erectus, considered by many scientists to be a human ancestor that lived as much as 2 million years ago.  It was in the western Lake Turkana area where famous anthropologist Richard Leakey discovered the most complete early human fossil skeleton ever found. Called Turkana_Boy, it was dated to 1.5 million years B.P.E. and was classifiable to either early Homo erectus or Homo ergaster.  It is to this day considered to be one of the benchmark finds for early humans.  

The Acheulian tools at Kokiselei were located immediately above a sediment layer associated with a polarity reversal called the “Olduvai Subchron", named after Olduvai Gorge in Tanzania where famous anthropologists Louis and Mary Leakey made their history-making hominin fossil and Oldowan stone tool finds in the 1930's. In a recent study conducted by Lepre and Kent, they determined that a Homo erectus skull found at Koobi Fora Ridge on the east side of Lake Turkana was also located above the Olduvai Subchron interval. This meant that the Homo erectus skull and the Acheulian tools in West Turkana were about the same age.

This early human species is also thought to be the first that dispersed on a global level, ranging across both Asia and Africa before becoming extinct possibly about 70,000 years ago. Many researchers suggest that Homo erectus evolved in East Africa, where many of the oldest fossils have been discovered; however, the discovery of equally ancient Homo erectus fossils at Dmanisi in the Republic of Georgia in the 1990s has led other researchers to suggest a possible Asian origin. The puzzling question is that Homo erectus in Dmanisi, Georgia was still using the simpler Oldowan-like chopping tools, when now in West Turkana, according to the new study, early humans had already developed the more sophisticated hand axes, picks and other innovative tools that anthropologists have assigned to the Acheulian. Add to this the evidence of two separate stone tool industries, the simpler, more primitive "chopper" technology of the Oldowan, and the more sophisticated, chiseled-edge technology of the Acheulian, existing side-by-side within the same time horizon at Kokiselei, and a more complicated picture emerges. The study results, in light of the Dmanisi finds, have presented new implications for the timing and dispersal of Homo erectus and the Acheulian industry, and directs the researchers to an interesting new hypothesis. 

States Lepre, et.al.:

"Our data indicate that the earliest development of the Acheulian occurred in Africa at 1.76 Myr ago and was contemporaneous with or perhaps pre-dated the earliest hominin dispersals into Eurasia. Yet, the difference between the ages for the oldest known Acheulian artefacts in the world from Africa and the oldest known Acheulian artefacts from Eurasia raises the likelihood that the first Eurasian hominins derived from an African population lacking Acheulian culture. Potentially, two hominin groups coexisted in Africa at 1.76Myr ago. One of these groups could have developed the Acheulian technology but remained in Africa. The other could have lacked the cognitive ability and/or technological knowledge to manufacture the Acheulian technology and did not carry it into Eurasia. This division may indicate different behavioural aptitudes for separate African species (for example, H. erectus sensu lato versus Homo habilis sensu lato) or a within-species cultural disparity. In any event, it seems that a second hominin dispersal with Acheulian technology or a diffusion of this technology took place later, leading to the widespread occurrence of this Early Stone Age tradition in the circum- Mediterranean area and elsewhere after 1 Myr ago."[1]

 

The researchers now hope to uncover more about the ancient environment in which the early humans lived, shedding new light on how environmental elements and their change effected the course of human evolution. Scientists know now that the East African landscape was becoming generally drier over a period of millions of years, with periodic wet and drier periods, but generally changing from a predominantly woodland environment to that of savannah grassland. 

Says Lepre, “We need to understand also the ancient environment because this gives us an insight into how processes of evolution work—how shifts in early human biology and behavior are potentially caused by changes in the climate, vegetation or animal life that is particular to a habitat.” 

They are currently excavating a site in Kenya more than 2 million years old to obtain a better understanding of the earlier Oldowan period.

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The tools made by early humans at Kokiselei, Kenya, were found in Lake Turkana's ancient shoreline sediments pictured above. Credit: Lamont-Doherty Earth Observatory.

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The study’s other authors are: Helen Roche, Sonia Harmand, Jean-Philippe Brugal, Pierre-Jean Texier and Arnaud Lenoble at France’s National Center of Scientific Research; Rhonda Quinn, Seton Hall University; and Craig Feibel, Rutgers University.

Full details of the study can be accessed in this week's edition of the journal Nature. 

Institutions involved in the study are:

The Earth Institute, Columbia University , which mobilizes the sciences, education and public policy to achieve a sustainable earth. Through interdisciplinary research among more than 500 scientists in diverse fields, the Institute is adding to the knowledge necessary for addressing the challenges of the 21st century and beyond. With over two dozen associated degree curricula and a vibrant fellowship program, the Earth Institute is educating new leaders to become professionals and scholars in the growing field of sustainable development. We work alongside governments, businesses, nonprofit organizations and individuals to devise innovative strategies to protect the future of our planet. www.earth.columbia.edu

Lamont-Doherty Earth Observatory A member of The Earth Institute, it is one of the world's leading research centers seeking fundamental knowledge about the origin, evolution and future of the natural world. More than 300 research scientists study the planet from its deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean. From global climate change to earthquakes, volcanoes, nonrenewable resources, environmental hazards and beyond, Observatory scientists provide a rational basis for the difficult choices facing humankind in the planet's stewardship. www.ldeo.columbia.edu

Notes:

[1] Christopher J. Lepre, He ́le`ne Roche, Dennis V. Kent, Sonia Harmand, Rhonda L. Quinn, Jean-Philippe Brugal, Pierre-Jean Texier, Arnaud Lenoble & Craig S. Feibel; An earlier origin for the Acheulian, doi:10.1038/nature10372.

Cover Photo, Top Left: Early humans were using stone hand axes as far back as 1.8 million years ago. Credit: Pierre-Jean Texier, National Center of Scientific Research, France.

Photo, Second from Top, Right: Study co-author, Craig Feibel, is among the team of researchers that returned in 2007 to West Turkana to put dates on hand axes excavated earlier. Credit: Lamont-Doherty Earth Observatory.

Photo, Third from Top, Left: Homo erectus fossil skull. Courtesy Joop Anker, Creative Commons Attribution-Share Alike 2.0 Generic

By Dan McLerran

As Founder and Editor of Popular Archaeology Magazine, Dan is a freelance writer and journalist specializing in archaeology.  He studied anthropology and archaeology in undergraduate and graduate school and has been an active participant on archaeological excavations in the U.S. and abroad.  He is the creator and administrator of Archaeological Digs, a popular weblog about archaeological excavation and field school opportunities.