A new genomic analysis of people currently living in Egypt and Ethiopia suggests that Eurasians originated when early Africans moved north – through the region that is now Egypt – to expand into the rest of the world. The findings answer a long-standing question as to whether early humans emerged from Africa by a route via Egypt, or via Ethiopia.
Genetic information from Ethiopians and Egyptians point to a Northern exit out of Africa as the most likely route by the ancestors of all Eurasians. Image credit: Luca Pagani.
To uncover the migratory path that the ancestors of present-day Eurasians (Europeans and Asians) took when moving out of Africa around 60,000 years ago, an international team of scientists generated 225 whole-genome sequences from six modern Northeast African populations (100 Egyptians and five Ethiopian populations each represented by 25 people).
In previous research, the scientists have shown that these modern populations have been subject to gene flow from West Asian populations, so they excluded the Eurasian contribution to the genomes of the modern African people.
The remaining masked genomic regions from Egyptian samples were more similar to non-African samples and present in higher frequencies outside Africa than the masked Ethiopian genomic regions, pointing to Egypt as the more likely gateway in the exodus to the rest of the world.
“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 Dr Luca Pagani of the University of Cambridge and the Wellcome Trust Sanger Institute.
The researchers also used high-quality genomes to estimate the time that the populations split from one another: people outside Africa split from the Egyptian genomes more recently than from the Ethiopians (55,000 as opposed to 65, 000 years ago), supporting the idea that Egypt was last stop on the route out of Africa.
“In our research, we generated the first comprehensive set of unbiased genomic data from Northeast Africans and observed, after controlling for recent migrations, a higher genetic similarity between Egyptians and Eurasians than between Ethiopians and Eurasians. This suggests that Egypt was most likely the last stop on the way out of Africa,” said Dr Pagani, who is the first author of the paper reporting the results in the American Journal of Human Genetics.
In addition, Dr Pagani and co-authors have also developed an extensive public catalog of the genomic diversity in Ethiopian and Egyptian populations.
“This information will be of great value as a freely available reference panel for future medical and anthropological studies in these areas,” Dr Pagani said.
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Luca Pagani et al. Tracing the Route of Modern Humans out of Africa by Using 225 Human Genome Sequences from Ethiopians and Egyptians. American Journal of Human Genetics, published online May 28, 2015; doi: 10.1016/j.ajhg.2015.04.019
