For decades, scientists have worked to unravel the mystery of modern humans’ journey out of Africa. Three recent studies point to a possible answer: a single great migration out of the African continent.
The three studies looked at a combined 800 sequenced genomes from people around the world in more than 270 population groups. Scientists used the data to analyze similarities and differences between different populations, which helped point the way back to a common ancestor. The vast majority of non-African modern humans appear to be descended from a single group of pioneers who left Africa between 50,000 and 80,000 years ago.
One study, led by Harvard scientists David Reich and Swapan Mallick, sequenced 300 genomes across 142 small populations and saw a huge reduction in Eurasian genetic diversity stemming from 60,000 years ago, which points to a single group leaving Africa at once. Another study, led by Eske Willerslev of the University of Copenhagen found Australian aborigines diverged from Eurasians between 50,000 and 70,000 years ago, after a larger group first migrated out of Africa.
While the third study, led by Mait Metspalu of the Estonian Biocentre, found similar results, they also discovered that two percent of the genome of people from modern Papua New Guinea dates from even further back in time. That bit of genetic evidence might point to an even earlier dispersal of modern humans, as far back as 120,000 years ago.
“As population geneticists, we could spend the next decade arguing about that two percent, but in practical terms it doesn’t matter,” said Joshua Akey, an evolutionary geneticist at University of Washington who wasn’t involved with any of the research. This is because the remaining two percent doesn’t
Lorraine Boissoneault is a writer in Chicago who covers science, history, foreign affairs, and adventure. She's written for Weather.com, Salon, Forbes, JSTOR Daily and many others. Her first book, The Last Voyageurs, was published by Pegasus in April 2016.