A genomic analysis shows that interbreeding between female Neanderthals and male modern humans was less frequent than the reverse combination.
Sexual preferences in prehistoric times helped shape the human genome, according to a study using genetic material from three female Neanderthal specimens, published this Thursday in the journal Science.
The analysis suggests that women A wise man interbred with Neanderthals (Homo neanderthalensis) com higher frequency than men H. sapiens with Neanderthal women.
The conclusions demonstrate how behavior can influence human evolution, he says Alexander Platt, study co-author and evolutionary geneticist at the University of Pennsylvania in Philadelphia.
“Human geneticists have often adopted a strangely clinical when analyzing ancient genomes. But these are all people, and we know that people have prejudices and preferences“, highlights the researcher.
Determine chow people behaved in the past it is an arduous task. In recent years, some studies have turned to genetics to understand how historical events, such as colonization and slaveryshaped the genomes of current populations. However, this approach rarely extends beyond modern history.
Since the human genome was sequenced 15 years ago, several scientific studies have shed light on hitherto unknown aspects of these ancestral humans — namely, who were passed on to small fragments of DNA that are still present in our genome today.
Modern humans can have . However, this genetic material is not evenly distributed.
Some regions of the genome of H. sapiens, including most of the X chromosome, do not show any ancestry Neanderthal. These regions are known as “Neanderthal deserts”.
They exist two main theories to explain the existence of these deserts. The first argues that the Neanderthal genetic variants were disadvantageous both for anatomically modern humans and for Neanderthals themselves, having been quickly eliminated from the human population.
The second holds that Neanderthal versions of certain genes were harmful to modern humansbut they worked perfectly for Neanderthals — and vice versa. In this case, we would expect Neanderthals with some human ancestry to have their own DNA desertsdevoid of human ancestry.
Most studies of Neanderthal DNA deserts analyze modern human genomes. Platt wanted, however, to examine the other side of the issue and understand how the Human DNA was integrated into Neanderthal genomes.
To this end, his team analyzed the genomes of three female Neanderthals who lived 122,000, 80,000 and 52,000 years ago, respectively. They all presented remote human ancestry.
Platt and his team identified human DNA deserts across much of the genome — with one notable exception. THE X chromosome Neanderthal contained, on average, 62% more human DNA than non-sex chromosomes.
This DNA did not appear to confer any advantagesince most were found in regions of the genome that do not code for proteins.
Non-random pairing
A population model developed by Platt and his colleagues suggests that this excess DNA can be explained by a sex-linked bias.
The surplus would have arisen if, over several generations, women H.sapiens if they had crossed with Neanderthals more frequently than Neanderthal women with H.sapiens men.
A reason for this preferential pairing is not clear. It may have resulted fromchoice of female, availability of partnerscultural acceptance of certain combinations or other factors, explains Sohini Ramachandrana population geneticist at Brown University who was not involved in the study, told the magazine .
The findings are “really exciting,” says Ramachandran. Behavior is often an underappreciated component of human evolution, he says, but the study shows that sexual bias was “something that played an important role in the interaction between humans and Neanderthals.”
Other researchers are more cautious. “I would say that it is an intriguing idea and that it seems to fit the pattern”, he says Leonardo Iasievolutionary geneticist at the Max Planck Institute for Evolutionary Anthropology, in Leipzig, Germany. “But it is very difficult to demonstrate conclusively that this is what really happened.”
Still, human geneticists have often treated historical populations as if people “they simply crossed paths at random and reproduce”, he observes. “Obviously, that’s not what happened“.
