Scientists may be one step closer to tracing the exodus of modern humans out of Africa. New genetic evidence points to a northern route leading out of the continent, which may just settle a long-disputed question concerning human migrations.

We are all African. The evidence elucidating our origins - both fossil and genetic - shows that modern humans arose in Africa some 200,000 years ago and started venturing forth about 150,000 years later. But the route with which they left the continent had yet to be resolved. That is, until now.

"Two geographically plausible routes have been proposed," says Dr. Luca Pagani, a researcher with the Wellcome Trust Sanger Institute and the University of Cambridge in the UK. "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."

To answer this question, Pagani and colleagues analyzed genetic data from six Northeast African populations (100 Egyptians and five Ethiopian populations, each represented by 25 people) and compared it to data obtained from populations in the Middle East and East Asia.

"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," Pagani says, which indicates that Egypt was most likely the last stop on the way out of Africa.

But like much of paleoanthropological research, there is disagreement.

"It is a very difficult question they are trying to address," cautioned Professor Rasmus Nielsen of the University of California, Berkeley. "I'm perhaps less optimistic than the authors on the possibility of identifying specific migration routes using present populations," says Neilson, based on the fact that the populations sampled have moved around frequently within the past 50,000 years.

But Pagani remains optimistic. Not only does his data help clarify potential migratory paths, it also provides insight into the evolutionary past of all Eurasians. The scientists are developing an extensive public catalog of genomic diversity in Ethiopian and Egyptian population, which can be used in future investigations. "This information will be of great value as a freely available reference panel for future medical and anthropological studies in the area," says Pagani.

"The most exciting consequence of our results is that we draw back the veil that has been hiding an episode in the history of all Eurasians, improving the understanding of billions of people of their evolutionary history."