We all know Homo sapiens evolved in Africa and then spread across the rest of the world. But scientists have demonstrated that, starting around 5000 B.C.E., an astoundingly large group came back. This “backflow” brought so many people from Eurasia that today’s East Africans get as much as 25% of their genome from Middle Eastern ancestors. In other words, about a quarter of their ancestors were Middle Eastern migrants. And even in southern Africa, thousands of miles away, the people get about 5% of their genes from backflow migrants. In fact, the Khoe-San of southern Africa get some of their pale skin genes — an advantage in sun-poor lands far from the equator — from these Eurasians.
We know because of a genetic study on a man who died in East Africa around 2500 B.C. His genes tells us what the pre-backflow genome looked like, so scientists can compare that population to modern Africans.
Interestingly, the backflow migrants were related to the population that had migrated in large numbers from the Middle East to Europe around 6000 B.C., bringing farming with them (Europe’s Neolithic Revolution). So Europeans and Africans share the genes of these Middle Easterners.
Illustration: A Nobleman of Tigre, T. Lefebvre and others, 1849
© 2015, 2021 by David W. Tollen. All rights reserved.