Wednesday, February 21, 2018

Ancient human DNA: How sequencing the genome of a boy from Ballito Bay changed human history

Marlize Lombard, Mattias Jakobsson, Carina Schlebusch
South African Journal of Science
January/February 2018
(Link) pdf

From the article: 

"The context of the three Stone Age hunter–gatherers (who displayed no recent admixture with migrating farmers and pastoralists), coupled with the high-quality DNA coverage obtained for the boy from Ballito Bay, provided us with the unique opportunity to recalculate the genetic time depth for our species (Homo sapiens) to between 350 000 and 260 000 years ago. Previously, the deepest genetic split was considered to have been between about 160 000 and 100 000 years ago.  And, based on fossil material from Ethiopia, the oldest modern humans were thought to have lived about 190 000 years ago in East Africa. Our work demonstrates that it is the context of human remains that matters when looking at potential deep splits in our lineage, and not their age. However, full-genome data from older remains may yet reveal more surprising outcomes. For example, any additional gene flow into southern African Stone Age populations, predating 2000 years ago, will increase the time depth of the first H. sapiens population split."

"The new genetic split-time estimate1 coincides with the interpretation of fossil material from Morocco in North Africa, dated to about 300 000 years ago16, which is seen as anatomically transitional between archaic and modern H. sapiens. It is also consistent with the age of the Florisbad skull that was found in the Free State, South Africa, dated to 260 000 years ago.  The Florisbad remains were discovered with Middle Stone Age artifacts, and have been referred to as archaic H. sapiens, representing a combination of archaic and modern characteristics with a cranial volume similar to that of modern humans of about 1300 mL. Other human remains from South Africa dating to between 300 000 and 200 000 years ago are those from Hoedjiespunt, currently ascribed to H. heidelbergensis, because although they are morphologically modern, they seemed larger than modern Africans."

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