It turns out interbreeding wasn't the reason that a group of Neanderthals in Western Europe died out, according to a new study in Nature.
It was previously thought that Neanderthal populations died out because mating between close relatives caused genetic ill-health. Researchers have found evidence in other, earlier groups of interbreeding significant enough to cause low genetic diversity – similar to some endangered species today.
But that doesn't seem to have been the case for one particular population. Scientists studied DNA from 27 individuals who lived in the Meuse Basin, spanning Belgium and France, between 40,000 and 49,000 years ago – shortly before Neanderthals disappeared entirely.
Their analysis found almost no mating between close relatives, even up to the third-degree level (the relatedness of first cousins, sharing about 12.5 per cent of their DNA).
“This population in Belgium and France does not seem to be dying out, even though we know that they will die out in the end,” said study author Dr Benjamin Peter, a computational geneticist at the Max Planck Institute for Evolutionary Anthropology, Germany.
Prof Omer Gokcumen, an expert in evolutionary anthropology at the University at Buffalo, New York State – who was not involved in the study – told BBC Science Focus: “Neanderthal data are so scarce that any new genome is a revelation.”
He added: “This runs counter to the idea that Neanderthals, towards the end, were a sickly population due to inbreeding, which drove their demographic collapse. So, the question remains: why did their population shrink and eventually get absorbed by modern humans?”
Neanderthals thrived across Europe and the Middle East for hundreds of thousands of years, surviving large variations in climate and the arrival of modern humans – until they died out around 40,000 years ago.
Climate change, resource competition and interbreeding with modern humans have all been suggested as factors in their demise.
Gokcumen noted that this new paper supports the idea that the fate of Neanderthal groups may have differed across regions, suggesting multiple contributing factors rather than one sweeping cause.
Prof Chris Stringer, honorary professor at University College London and scientific associate at the Natural History Museum – also not involved in the study – said the paper suggested the need to “look at other factors [other than interbreeding] in their extinction”.
He added: “The unidirectional pattern of gene flow into modern human populations supports my suggestion that late Neanderthals were losing fertile individuals to Homo sapiens groups in a one-way process, which could well have contributed to their demise.”
In other words, fertile Neanderthals may have been steadily drawn into Homo sapiens groups through interbreeding, in a one-way loss the Neanderthal population couldn't make up.
Read more:
