09 November 2012

Ancient humans in the southern African environment

I try not to miss the interesting Africa Genome Education Institute’s Darwin lectures that are held at UCT Medical School. The last of the 2012 lectures was deliverd by our internationally renowned geneticist, Prof Himla Soodyall from Wits University’s Division of Human Genetics.

Genetics hones in on Africa’s human origins.

Pinpointing the exact place of origin of anatomically modern humans in sub-Saharan Africa is something that still has the scientific community raging in debate – was it in Central, Eastern, Western or Southern Africa? However, advances in the field of genetics, used alongside with other traditional means of tracking human history, is going a long way towards opening up a more complex view of our ancient past.

Looking at the genes of different black African population groups from across the region, acclaimed geneticist Prof Himla Soodyall from Wits University’s Division of Human Genetics said it was evident that these population groups carried genes that are closely related to those of an ancient line linked to the Khoe and San. The Khoe-San, meanwhile, carry a genetic line which traces directly to a genetic pool dating back to 100 000 years ago. This suggests that Khoe and San women assimilated widely into other populations across the region.

Speaking at the final lecture in the 2012 Africa Genome Education Institute’s Darwin lecture series on 24 October, Soodyall explained how other lines of scientific enquiry – such as paleo-anthropology, archaeology and linguistics – gave different clues as to the origin of the first modern humans, before small groups of them left the continent and went on to populate the rest of the world.

“East Africa usually comes up trumps as a likely point of origin, because they had volcanic activity in this region which has allowed better dating of fossils discovered there. It has the beautiful fossil remains of the pre-humans, the Australopithecines. And the region has some modern human genetic diversity,” she explained.

But Southern Africa is also a strong contender.

“We have footprints of modern humans at Langebaan. We have archaeological sites like Pinnacle Point near Mossel Bay where human presence in the form of tool making and the use of fire to make tools, which harbours information on how we became behaviourally advanced and modern.”

The region also has rock art sequences that are much older than the earliest site in France.

Soodyall said a multidisciplinary approach, using different tools such as archaeology, linguistics and genetics, was necessary in order to get different resolutions on our history.

“If you were to ask what it was like 10 000 years ago in terms of people living on the African continent, DNA would not be the method of choice. The archaeological record might be able to give more convincing ideas about what landscape the people occupied, how they hunted, and so on.”

However, genetics has been able to show that most people on Earth trace to a pool of modern humans that dates back to about 50 000 years, while the Khoe and San link to a genetic pool that dates back to about 100 000 years ago. Similarly, a study of genetics in this way has allowed us to see that all humans living today are descended from a population that came out of Africa.

“Using these different tools, each of which convergences back into the past in its own way, and we have a nice view from all sides of the room with windows in different parts of the walls. Some windows will allow us to look further back into the past than others.”

But on the still contentious question of precisely where in sub-Saharan Africa modern humans originated from, Soodyall was bullish.

“If I were a betting person, I’d put my money on backing the Southern African story.”

If anyone is interested in this series, that we hope will continue in 2013, contact Beryl at Hippo communications and ask to be included on their email list.

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