Leaving the nest: early humans migrated from Africa through North, rather than South

Archaic Homo sapiens left Africa, the wellspring of humanity, some 60,000 years ago migrating North, via a route passing through today’s Egypt, rather than South, through the Arabian Peninsula, as previously proposed. The findings were reported by an international team of researchers which used novel techniques to produce whole-genome sequences from 225 people from modern Egypt and Ethiopia (six modern Northeast African populations). This is far from a definite conclusion, but the picture researchers paint seems to be consistent with other evidence, such as early human-made tools and human fossils found on the proposed route (Israel), and is in better agreement with what we already know about the genetic mixture of all non-Africans with Neanderthals.

The “out of Africa” theory (OOA), is the most widely accepted model of the geographic origin and early migration of anatomically modern humans. The date of the earliest successful “out of Africa” migration (earliest migrants with living descendants) has generally been placed at 60,000 years ago based on genetics, but migration out of the continent may have taken place as early as 125,000 years ago according to Arabian archaeological finds of tools in the region.

“Two geographically plausible routes have been proposed: an exit through the current Egypt and Sinai, which is the northern route, or one through Ethiopia, the Bab el Mandeb strait, and the Arabian Peninsula, which is the southern route,” said Luca Pagani, one of the researchers, in a news release. “In our research, we generated the first comprehensive set of unbiased genomic data from Northeast African and observed, after controlling for recent migrations, a higher genetic similarity between Egyptians and Eurasians than between Ethiopians and Eurasians.”

Once the researchers sequenced the genome for each individual in the Northeast Africa populations, they had to filter the genes for modern influences like gene flow from West Asian populations. The masked genome samples from the Egyptian populations were more similar to non-African samples and present in higher frequencies outside Africa than the masked Ethiopian genomic regions. This suggests Egypt, or by North, as a more plausible route for the human exodus from its African cradle. Moreover, the team also estimated  the time that the populations split from one another. Non-Africans split from the Egyptian genomes more recently than the Ethiopians, specifically 55,000 versus 65,000 years ago respectively.

“While our results do not address controversies about the timing and possible complexities of the expansion out of Africa, they paint a clear picture in which the main migration out of Africa followed a Northern, rather than a Southern route,” says Dr Toomas Kivisild, a senior author from the Department of Archaeology and Anthropology, University of Cambridge.

So far, the evidence is compelling enough to suggest Egypt was the last stop in the migration pattern. Far from a sealed fact, the research published in the American Journal of Human Genetics, provides a valuable foothold for scientists studying other instances like medical and anthropological studies in these areas.

“This important study still leaves questions to answer,” says Dr Chris Tyler-Smith, a senior author from the Wellcome Trust Sanger Institute. “For example, did other migrations also leave Africa around this time, but leave no trace in present-day genomes? To answer this, we need ancient genomes from populations along the possible routes. Similarly, by adding present-day genomes from Oceania, we can discover whether or not there was a separate, perhaps Southern, migration to these regions.

“Our approach shows how it is possible to use the latest genomic data and tools to answer these intriguing questions of our human origins and migrations.”

 

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