A member of the Hadza tribe of Tanzania, a young boy practices his archery skills. (Credit: Image courtesy of University of Pennsylvania)
Human diversity in Africa is greater than any place else on Earth. Differing food sources, geographies, diseases and climates offered many targets for natural selection to exert powerful forces on Africans to change and adapt to their local environments. The individuals who adapted best were the most likely to reproduce and pass on their genomes to the generations who followed.
That history of inheritance is written in the DNA of modern Africans, but it takes some investigative work to interpret. In a report to be featured on the cover of the Aug. 3 issue of the journal Cell, University of Pennsylvania geneticists and their colleagues analyze the fully sequenced genomes of 15 Africans belonging to three different hunter-gatherer groups and decipher some of what these genetic codes have to say about human diversity and evolution.
It identifies several million previously unknown genetic mutations in humans. It finds evidence that the direct ancestors of modern humans may have interbred with members of an unknown ancestral group of hominins. It suggests that different groups evolved distinctly in order to reap nutrition from local foods and defend against infectious disease. And it identifies new candidate genes that likely play a major role in making Pygmies short in stature.
“Our analysis sheds light on human evolution, because the individuals we sampled are descended from groups that may have been ancestral to all other modern humans,” Tishkoff said. “A message we’re seeing is that even though all the individuals we sampled are hunter-gatherers, natural selection has acted differently in these different groups.”