New research at the University of Cambridge reveals that the modern human genome was created as a result of a merger between two ancient populations, which separated about 1.5 million years ago and reunited about 300 years ago.
Scientists have discovered evidence that modern humans evolved from two separate ancient populations and not from a single population, as previously believed.
This genetic encounter reshaped the human species, introducing key traits that may have influenced brain function. Unlike interbreeding with Neanderthals, this ancient event contributed a much more significant portion of human DNA.
Researchers at the University of Cambridge used whole genome analysis to find evidence that the genome of modern humans is the result of a fusion event between two ancient populations that diverged about 1.5 million years ago. About 300 years ago, they reunited, with one contributing about 80% of the genome and the other about 20%.
"Our history is richer and more complex than we thought," said Professor Aylwin Scully of the Department of Genetics at Cambridge.
For the past two decades, the prevailing view was that modern humans emerged in Africa 200-300 years ago from a single population. The new study, published in the journal Nature Genetics, suggests a more complex story.
"The question of where we came from has fascinated humanity for centuries," said Dr. Trevor Cousins, who led the study. "Our research shows clear signs that our origins are much more complex, and that groups that evolved separately for over a million years reunited to form the modern human species."
Evidence of ancient genetic fusion And its effect on the brain
Previous studies have already shown hybridization with Neanderthals and Denisovans about 50 years ago, but the new study indicates a much older and more significant fusion, which constitutes up to 20% of the modern human genome, in contrast to only 2% of Neanderthals.
The researchers relied on genome analysis of modern humans rather than DNA from ancient bones. To do this, they developed an algorithm called cobraa, which was tested on data from simulations as well as data from the global "1000 Genomes" project.
The study revealed that after the split, one of the populations experienced a dramatic decline, but later grew to become the source of 80% of the genome of modern humans. This population was also the source from which Neanderthals and Denisovans evolved.
Some of the genes that came from the second population, although in a minority, are related to brain function and may have been essential in human evolution. These genes were often far from key functional regions of the genome, suggesting a process of purifying selection that removed harmful mutations over time.
Beyond Humans: A New Evolutionary Framework
The researchers believe that the method they developed may change the way the evolution of other species is studied, and have even identified ancient population structures in bats, dolphins, chimpanzees, and gorillas.
"The idea that species evolved along clean, clear lines is too simplistic," Cousins explained. "Hybridization and gene exchange have played a significant role in the emergence of new species throughout history."
Who were the mysterious ancestors??
The fossils point to species such as Homo erectus and Homo heidelbergensis as possible candidates, but further studies are needed to definitively identify which fossils correspond to which genetic ancestors.
"The very ability to reconstruct events from hundreds of thousands or millions of years ago just by examining modern DNA is amazing," concluded Prof. Scully.
More of the topic in Hayadan:
