An international team of scientists conducting an analysis of the genetic diversity and cranial measurements of 10 African and Asian human populations conclude that anatomically modern humans may have dispersed out of Africa earlier than previously thought, and in more than one stage: initially into Asia by taking a southern route through Arabia as much as 130,000 years ago; and later into Northern Eurasia on a more northerly route 50,000 years ago.
The timing and nature of early modern human dispersal out of Africa has long been disputed among scholars, with competing theories or models about how and when it all occurred. The research team analyzed their data within the framework of the competing models, and came up with the model that best fits the results. “We tested for the first time to our knowledge the spatiotemporal dimensions of competing out-of-Africa dispersal models,” write Hugo Reyes-Centeno and colleagues in their report, “analyzing in parallel genomic and craniometric data. Our results support an initial dispersal into Asia by a southern route beginning as early as ∼130 ka and a later dispersal into northern Eurasia by ∼50 ka.”* Reyes-Centeno is a paleoanthropologist with the Senckenberg Center for Human Evolution and Paleoenvironment, Eberhard Karls University of Tübingen, Germany. Other researchers included Katerina Harvati, also of Eberhard Karls University; Silvia Ghirotto and Guido Barbujani of the University of Ferrara, Ferrara, Italy; and Florent Détroit and Dominique Grimaud-Herve of the National Museum of Natural History, Paris, France.
“This is consistent with archaeological evidence for modern human occupation in the southern Arabian Peninsula at ∼125 ka,” write the authors. “This date [130,000 ka] is in intriguingly closer correspondence with the genetic divergence estimates for our sampled populations, with a calendar date of divergence between Melanesians and South Africans at ∼116 ka, for example. No modern human fossils have been discovered in the southern Arabian Peninsula, but lithic artifacts show affinities with African assemblages, including those discovered alongside the fossil remains at Herto, Ethiopia, dated between ∼154–160 ka.”*
Genetic studies and fossil evidence show that the first common ancestral population of modern humans resided in Africa between ∼100–200 ka, and that members of one branch left Africa by between 125,000 and 60,000 years ago. A prominent theory suggests that over time these humans replaced earlier human populations such as Neanderthals and Homo erectus. Many scholars posit that the date of the earliest successful “out of Africa” migration took place about 60,000 years ago, according to genetic evidence, although recent archaeological finds on the Arabian Peninsula have suggested the possibility of a much earlier migration.
The study report was published April 21, 2014 in the Proceedings of the National Academy of Sciences.
*“Genomic and cranial phenotype data support multiple modern human dispersals from Africa and a southern route into Asia,” by Hugo Reyes-Centeno et al. http://www.pnas.org/cgi/doi/10.1073/pnas.1323666111
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