There are traces of Neanderthal DNA in the DNA of modern humans — we have 1 to 4 percent Neanderthal genes. This indicates that the two species interbred in the past. Until now, most genetic analyses have examined gene flow from Neanderthals to modern humans.
Now, scientists have reversed course and traced the flow of genetic material from humans to Neanderthals. The results have shocked experts.
The analyses revealed that the special relationship between the two species may be as old as 250,000 years. Neanderthal DNA showing traces of such early interbreeding has led experts to conclude that Previous studies have overestimated the overall Neanderthal population size by as much as 20 percent.
As the researchers write: “The smaller estimated population size and inferred admixture dynamics are consistent with a Neanderthal population that declined over time and it was eventually absorbed into the gene pool of modern humans“.
Among Neanderthals living in Africa, high heterozygosity of DNA sequencesindicating that the DNA may have come from individuals that resulted from interbreeding with modern humans. In contrast, the DNA of non-African Neanderthals showed low levels of heterozygosity, suggesting sporadic interbreeding between the two species.
This discovery allowed the researchers to identify two specific pulses of gene flow. The first occurred from 250,000 to 200,000 years agoand the second one from 120,000 to 100,000 years ago.
During the research it was noticed that Neanderthals from Vindija (northern Croatia) and Altai had respectively about 2.5 percent and 3.7 percent of human DNA. This may suggest the aforementioned overestimation of the Neanderthal population size. Further, this information may contribute to explaining the issue of the Neanderthal extinction. New research confirms the previously proposed thesis that the Homo sapiens population absorbed the Neanderthal population.
“The assimilation of Neanderthals into modern human populations as they spread throughout Eurasiawould have effectively increased the size of modern human populations while simultaneously reducing the size of the already endangered Neanderthal population,” the researchers write.
They add: “Our finding that the Neanderthal population size was probably even smaller than previously estimated would only have accelerated the assimilation process, and the replacement Y chromosome and mitochondrial DNA in late Neanderthals by modern humans may have set the course irrevocably for the disappearance of one of the few remaining hominin lineages that coexisted with modern humans.”
The research results were published in the journal Science.
Source: geekweek.interia.pl
