Researchers from Estonia and Italy developed an innovative method by combining neural networks and statistics. With this newly developed method, they refined the “Out of Africa” scenario. The researchers claimed that the African dynamics around the time of the Out of Africa expansion were more complex than previously thought.
Archaeologists and geneticists agree that all modern humans originated somewhere in Africa some 300,000 years ago. The population movement that colonized the rest of the world took place around 60-70 thousand years ago. Both Y-chromosomal data (which follow the patrilinear line) and the mitochondrial genome (which follow the matrilinear line) match. However, the exact relationship between the people who left Africa and the people currently living on the continent is not fully understood.
A simplified model would see the first phase of subdivision of the population within Africa, followed by a separation between the ancestors of modern Eurasians and the ancestors of modern East or Northeast Africans. New Research (https://doi.org/10.1016/j.ajhg.2021.09.006) on the subject, recently published in the American Journal of Human Genetics, argues that expansion outside Africa was preceded by significant population shifts from east to west Africa. This event likely homogenized West and East Africans. This turnover, which can account for up to 90% of today’s West African gene pool, increased the affinity between West Africans and Eurasians. This event better explains the lower bound (about 60,000 years ago) derived from genetic data for the time of separation between Africans and non-Africans.
“A similar hypothesis was previously made for the Y chromosome. But this is the first time we’ve demonstrated it for autosomal DNA, ”said Francesco Montinaro, a lead author on this study from the University of Bari. Autosomal DNA comes from both parents, instead of Y chromosome or mitochondria, which comes from just one of our parents.
“It is fascinating to see how our understanding of the human past becomes more complex and detailed. Our new model can give us an indication of why West Africa has such a recent period of separation from the population outside Africa, ”said Vasili Pankratov, a senior co-author of the University of Tartu.