Scientists have revealed a hidden chapter in human evolution, showing our origins trace back to the interbreeding of two distinct species about 300,000 years ago.
By analysing modern human DNA, researchers from Cambridge University made the groundbreaking discovery that challenges previous understandings of human evolution as a single lineage.
Their results suggest that about 1.5 million years ago, our forebears split into two distinct species, similar to the separation of chimpanzees and bonobos.
After 1.2 million years apart, these two groups encountered one another and interbred.
Scientists have revealed a hidden chapter in human evolution, showing our origins trace back to the interbreeding of two distinct species about 300,000 years ago
GABRIEL UGUETO/UNIVERSITY OF CAMBRIDGE
This genetic mixing created the lineage from which all modern humans descend, according to the research published in Nature Genetics.
The research suggests that roughly 80 per cent of our genetic material comes from a population that had dwindled to perilously low numbers.
This group may have shrunk to perhaps as few as 1,000 individuals before the pivotal reunion.
"After the two ancestral populations split, we see evidence of a severe bottleneck in one of them," said Dr Aylwyn Scally from Cambridge's department of genetics.
This population later contributed the majority of our genome.
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Researchers from the University of Cambridge made the discovery (stock pic)
GETTYThe species responsible for the smaller genetic fraction also left a significant mark on our evolution.
Dr Trevor Cousins, who led the study, noted these genes were related to brain function.
"These may have played a crucial role in human evolution," Cousins said.
Until now, the prevailing view was that our species, Homo sapiens, first arose in Africa between 200,000 and 300,000 years ago.
This traditional understanding suggested we descended from a single lineage.
The new research from Cambridge paints a far more intricate picture of human origins.
Until now, the prevailing view was that our species, Homo sapiens, first arose in Africa between 200,000 and 300,000 years ago
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Fossils from the era point to two species, Homo erectus and Homo heidelbergensis, that inhabited Africa and other regions.
Either could be candidates for the ancestral groups identified in the study.
Earlier studies had shown that Neanderthals and Denisovans interbred with Homo sapiens about 50,000 years ago.
The Cambridge research suggests a far more significant genetic mixing event took place much earlier.
While Neanderthal DNA accounts for about two per cent of the genome of modern non-Africans, this ancient interbreeding left a far greater legacy.
The Cambridge team used computers to analyse modern human DNA based on data from the 1,000 Genomes Project.
"The question of where we come from has fascinated humans for centuries," said Cousins. "What's becoming clear is that the idea of species evolving in clean, distinct lineages is too simplistic.
"Interbreeding and genetic exchange have likely played a major role in the emergence of new species repeatedly across the animal kingdom."
