Out of Africa: Startling New Genetics of Human Origins

Posted: July 27, 2012 at 5:11 am

Western Pygmies

I love population genetics for its ability to peer back into human history through the medium of DNAs ATCGs.

One of the stars of this discipline is Sarah Tishkoff, a standout in African genetics, someone who will readily haul a centrifuge into the bush in Cameroon.

Tishkoff of the University of Pennsylvania is lead author on a paper published online July 26 inCell that details whole-genome sequencing of five individuals each from three extant hunter-gatherer groupsthe Pygmies of Cameroon as well as the Hadza and the Sandawe of Tanzania. The results reveal millions of newly discovered genetic variantsdifferences in single genetic letters, the ATCGsand indicate that early modern humans may have interbred long ago in Africa with another species of hominid (although the fossil record does not provide much support for the latter finding).

Tishkoff answered a few questions for us about this paper, co-authored with Joseph Lachance and 11 other researchers. An edited version of the interview appears below:

Please describe the research that led to the paper that was published today:

Were the first ones to look at these diverse groups of hunter-gathers in Africa who descend from some of the most ancestral lineages in the world. Theyre interesting because they have very unique and distinct lifestyles There are few populations that maintain this active hunter-gatherer lifestyle.

This is the most extensive study in Africa using high-coverage deeply detailed sequence data. We focused on three groups because theyre anthropologically interesting. Theyre thought to be descended from groups that are ancestral to all modern humans. We wanted to understand the genetic basis of adaptation to their local environment including, for instance the short stature trait in Pygmies.

So what did you find?

We discovered 13 million variants and, of those variants, greater than 3 million are completely novel, meaning that they have not been reported in any database. The current public database has 40 million variants. So we found 3 million novel variants by simply sequencing 15 individuals. That increases by about 8 percent all known human genetic variation. It also demonstrates that were missing a lot of really important variation thats out there, particularly in Africa, which is the homeland of modern humans and a place where theres been a lot of time for differentiation to have occurred in very diverse environments. What this means is that theres s probably a lot of regional or population-specific variation out there that has not been that well characterized, some of which is functionally very important.

See the original post here:
Out of Africa: Startling New Genetics of Human Origins

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