Fossil DNA Reveals New Insights into First Human Migration Out of Africa

Thousands of years ago, the first humans migrated out of Africa and spread across the globe. Hunters and gatherers, these ancient peoples crossed land bridges and pursued game in order to survive. Now, though, researchers have found that these first movements occurred less than 95,000 years ago, challenging the theory that people migrated far earlier.

The findings, published in the journal Current Biology, examined DNA from some of the oldest modern human fossils discovered so far. The research team reconstructed more than ten mitochondrial genomes (mtDNAs) from skeletons that spanned 40,000 years of prehistory. The remains included human fossils from the triple burial from Dolni Vestonice in the Czech Republic and from the site of Oberkassel in Germany.

The scientists used radiocarbon dating to find out how old the fossils were, and then estimated the human mutation rates by examining the mtDNA. How did they manage to estimate the mutation rates? They calculated the number of mutations in modern groups--absent in ancient groups--and counted the number of mutation accumulated along descendent lineages.

After examining the mtDNA, the researchers found that pre-ice age hunter-gatherers from Europe carried mtDNA that is related to post-ice age modern humans. They noted that this suggested that there was population continuity throughout the last major glaciation event in Europe, which occurred about 20,000 years ago.

In fact, the scientists estimate that the maximum date for the mass migration of modern humans out of Africa was a mere 95,000 years ago, but could have occurred as recently as 62,000 years ago. They noted that the results are actually in agreement with previous mitochondrial dates based on other work.

"The results from modern family studies and our ancient human DNA studies are in conflict," said Johansse Krause, one of the researchers, in a press release. "One possibility is that mutations were missed in the modern family studies, which could lead to underestimated mutation rates."

The findings have implications for how we understand the ancient history of modern humans. The DNA studies revealed that, in fact, humans migrated out of Africa far sooner than anyone once thought.