Modern people do not come from a single ancestral population, but at least from two, which have separated and then reunited long before modern people spread throughout the world.
Using an extensive analysis based on the complete sequences of the genome, researchers at the University of Cambridge have discovered evidence that modern people are the result of the genetic mix of two ancient populations, which have separated about 1.5 million years ago. About 300,000 years ago, these groups met, and one of them contributed 80% to the genetic composition of modern people, while the other added 20%.
In the last two decades, the dominant theory in human evolutionary genetics was that Homo Sapiens appeared for the first time in Africa 200,000-300,000 years ago, coming from a single ancestral line. However, these new discoveries, published in Nature Genetics magazine suggest a much more complex history.
“The question about our origin is concerned about people for centuries,” said Trevor Cousins, co -author of the study. “For a long time it was assumed that we come from a single continuous line, but the exact details of our origin remain unknown.”
“Our study clearly demonstrates that our evolutionary origin is more complicated and involves different groups that have developed separately for over a million years, before gathering to form the modern human species,” said Professor Richard Durbin, co-author of research.
Although previous studies have already shown that Neanderthals and Denisovans-two missing relatives of man-crossed with homo sapiens about 50,000 years ago, the new study suggests that, long before these interactions, about 300,000 years ago, a much more significant genetic mixture took place.
Unlike the Neanderthalians DNA, which represents about 2% of the genome of modern non-African people, this ancient mixing event has had an impact ten times higher and is present in all modern people.
The team based its method on the analysis of the modern human DNA, instead of extracting genetic material from ancient bones, which allowed them to identify the ancestral populations that would not have left physical traces. The data used in the study come from 1000 Genomes Project, a global initiative that has sequented the DNA of populations in Africa, Asia, Europe and America.
The researchers developed a computational algorithm called Cobraa, which shapes how the ancient populations of people separated and then met. They tested the algorithm on simulated data and then applied it on the real genetic data of 1000 Genomes Project.
Although the researchers managed to identify these two ancestral populations, they also discovered surprising changes that took place after their initial separation.
“Immediately after the two ancestral populations have separated, we notice a drastic reduction of one of them, which suggests that its size has decreased to a very small level, then slowly increasing for a million years,” explained Professor Aylwyn Scaly, co-author of the study. “This population later contributed about 80% of the genetic material of modern people and seems to have been the ancestral population from which Neanderthalia and Denisovans came.”
“However, some genes of the population that contributed to a smaller part to our genome, especially those related to the functioning of the brain and neural processing, could have played a crucial role in human evolution,” added Cousins.
