Katie Scott July 18, 2011
It has been a long held belief that our human ancestors came into contact with Neanderthals, and recent findings not only confirm this, but also suggest exactly how “close” this contact was.
Damian Labuda of the University of Montreal’s Department of Pediatrics and the CHU Sainte-Justine Research Center and team have found part of the human X chromosome comes from the Neanderthals and is found only in people outside of Africa.
In a paper published in the July issue of the journal Molecular Biology and Evolution, the geneticists write: “We provide evidence of a notable presence (nine percent overall) of a Neanderthal-derived X chromosome segment among all contemporary human populations outside Africa”. The team analyzed 6,092 X-chromosomes “from all inhabited continents”. Their discovery confirms earlier hypotheses that early modern man and Neanderthals mixed and mated.
The ancestors of the Neanderthals are believed to have left Africa between 400,000 to 800,000 years ago. However, by 30,000 years BC, they had disappeared. The ancestors of modern man left Africa between 80,000 and 50,000 years BC, suggesting that there was a definite crossover between the two.
Discovery News adds: “The team believes most, if not all, of the interbreeding took place in the Middle East, while modern humans were migrating out of Africa and spreading to other regions.”
This finding comes nearly ten years after Labuda and team identified a piece of DNA in the human X chromosome (called haplotype) that seemed different. A release detailing the findings explains: “When the genome of Neanderthals was sequenced in 2010, they quickly compared to 6,000 chromosomes from across the world with the haplotype of the Neanderthal. The sequence of the Neanderthal man was found in people of all continents, including Australia, but with the exception of sub-Saharan Africa.”
David Reich, a geneticist at Harvard Medical School, and one of the researchers involved in the project of deciphering the genome of Neanderthals says: “Labuda and his colleagues were the first to identify in non-African genetic variation may come from an archaic population. At the time, they have identified without access to the genome sequence of the Neanderthal. Today, in light of the Neanderthal genome sequence, it is clear that they were absolutely right.”