Fatal genetic incompatibility between Neanderthals Modern humans may have hastened the extinction of our ancient relatives, a new study suggests.
Researchers have found that different versions of a gene associated with red blood cell function may have caused miscarriages in female Neanderthal-human hybrids.
When Neanderthals and early modern humans met in Eurasia around 45,000 years ago“They exchanged genes—and may also have passed on hidden reproductive risks that determined the fate of both lineages.” Patrick Eppenbergerco-director of the Evolutionary Pathophysiology and Mummy Study group at the Institute of Evolutionary Medicine in Zurich, and his colleagues wrote in study published in the bioRxiv preprint database September 29. (It has not yet been peer reviewed.)
Researchers have focused on PIEZO1 genewhich affects red blood cells and occurs as in modern humans (wise man) and Neanderthals. They found that the PIEZO1 gene differs between Neanderthals and modern humans.
The Neanderthal variant, similar to a variant found in other great apes, allowed hemoglobin in red blood cells to bind more tightly to oxygen molecules, while the new variant X. sapiens the option allowed for more efficient transfer of oxygen to surrounding tissues. The researchers suggested that Neanderthals may have retained the original variant because it was useful for surviving extreme cold and periods of famine.
But when the mother's blood contains an abnormally high amount of oxygen bound to hemoglobin, it means that low levels of oxygen are being transferred to the fetus through the placenta. This may cause hypoxia (oxygen deficiency) or fetal growth restriction or miscarriage.
But because of the way PIEZO1 gene variants are inherited, incompatibility can only occur when a Neanderthal-human hybrid mother mates with a modern human father or a Neanderthal-human hybrid father.
“Many of their descendants will not survive,” the researchers write. This, in turn, would mean that Neanderthal women would pass on less of their mitochondrial DNA, which is carried in the egg and passed from mother to child, the study authors wrote. The researchers noted that over several generations of Neanderthal-human mating, this may have significantly undermined the ability of hybrid Neanderthals to have children.
“PIEZO1 incompatibility may have accelerated the extinction of Neanderthals by gradually destroying their reproductive capacity whenever the two groups interacted,” they write.
April NowellA paleolithic archaeologist at the University of Victoria, who was not involved in the study, told Live Science in an email that the study adds a much-needed piece of the puzzle to the Neanderthal extinction question: namely, maternal-fetal incompatibility in oxygen transfer during pregnancy.
“It’s very interesting that the allele [gene variant] What may have saved Neanderthals in the past became their eventual demise when they began interbreeding with modern humans,” Nowell said.
John Hawkesa biological anthropologist at the University of Wisconsin who was not involved in the study told Live Science in an email that PIEZO1 incompatibility between mother and fetus is intriguing and similar to other genetic blood disorders, such as Rh incompatibility in modern humans.
“This is one of many potential cases where a gene variant originating in an archaic population had some negative consequences, causing its frequency to decline over time in modern humans,” Hawkes said.
But PIEZO1 is not the final answer to the question of Neanderthal extinction.
“There is no single-gene explanation for what was a long and complex interaction between many archaic human groups as modern humans entered and interacted with the places where they lived,” Hawkes said.
Eppenberger and his colleagues stressed in their study that the effect of interbreeding between Neanderthals and modern humans was likely long-lasting and subtle—“more like rust weakening the structure than a single catastrophic blow”—and that more research is needed in this direction.
“It is worth wondering how many other loci in the genome could similarly cause hybrid incompatibility,” they wrote.
