Over the past few years, scientists have debated the reasons behind the extinction of Neanderthals, while modern humans thrived around 40,000 years ago. The new study, led by the Globe Institute, reinforces the idea that Neanderthals' social isolation and limited genetic diversity may have played a key role in their demise.
"When we look at these genomes from Neanderthals, we see that they are quite inbred and therefore don't have much genetic diversity. They have been living in small groups for many generations. We know that inbreeding reduces genetic diversity in a population, which can be detrimental to their ability to survive if it occurs over a longer term," explained Associate Professor Martin Sikora from the Globe Institute.
The recently discovered male Neanderthal genome in southern France belongs to a different lineage than those previously studied, further supporting the theory that Neanderthals lived in smaller, more isolated groups compared to early modern humans.
"The newly found Neanderthal genome is from a different lineage than the other late Neanderthals previously studied. This supports the notion that social organization of Neanderthals was different to early modern humans who seemed to have been more connected," Sikora added.
In contrast, early modern humans are believed to have maintained broader social networks, which could have helped them survive by allowing for the exchange of knowledge and genes between groups. "This is in the more speculative end, but even just the notion of being able to communicate more and exchange knowledge is something humans do that Neanderthals to some extent might not have done, due to their isolated lifestyles by organizing themselves in smaller groups. And that is an important skill to have," noted Postdoc Tharsika Vimala. She pointed to evidence of early humans in Siberia creating mating networks to avoid inbreeding, a practice that hasn't been observed among Neanderthals.
DNA Insights into Neanderthal History
Despite the abundance of Neanderthal remains found across Europe and Asia, researchers have extracted relatively few DNA samples from them. Some of the oldest Neanderthal DNA, dating back 120,000 years, has been found in caves such as Denisova Cave in the Altai Mountains, Scladina in Belgium, and Hohlenstein-Stadel in Germany.
The recently discovered genome from France is only the fifth Neanderthal genome of its kind found in Western Europe that's younger than 50,000 years. "Our team in Copenhagen extracted DNA from his tooth, sequenced the DNA and analyzed his nuclear genome, which is the DNA found within the core of the cells. The DNA was analysed along with other known Neanderthal genomes to understand their shared history," Sikora stated.
Further analysis of another late Neanderthal from France revealed that this individual also carried ancestry from a separate Neanderthal lineage, suggesting that multiple isolated groups may have coexisted in Western Europe shortly before their extinction.
While the concept of isolated Neanderthal communities contributing to their extinction is not new - having been proposed in relation to Neanderthals from the Altai Mountains - this latest discovery marks the first genomic evidence to support the theory in Western Europe.
"It is something that we have talked about for a while. But we needed more evidence, and this is some of the evidence that we were looking for and needed to figure out how likely this hypothesis of them going extinct because of their isolated lifestyle is. We do, however, need much more genomic data to paint a better picture of their history," added Vimala.
Research Report:Long genetic and social isolation in Neanderthals before their extinction
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