We all know Homo sapiens evolved in Africa and then spread across the rest of the world. But scientists have recently demonstrated that, around 1000 B.C., 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 genes from Middle Eastern ancestors. In other words, about a quarter of their ancestors were Middle Eastern migrants. And even in far Western and Southern Africa, more than 3,000 miles away, the people get at least 5% of their genes from backflow migrants.
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.
What could have caused such vast numbers to move? No one knows.
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. So Europeans and Africans share the genes of these restless Middle Easterners — particularly Europeans on the Mediterranean island of Sardinia, which has been partly isolated from the rest of the world for millennia and so preserves much of its original migrants’ genome.
Illustration: A Nobleman of Tigre, T. Lefebvre and others, 1849
© 2015 by David W. Tollen. All rights reserved.