In the blood the secret of the extinction of the Neanderthals

In the blood the secret of the extinction of the Neanderthals

The genomic sequences of three Neanderthals and a Denisovan confirm the crossing with the Sapiens and highlight a low genetic diversity that probably led to their extinction

(Photo: Getty Images) A ​​team of scientists from the research unit at Anthropologie Bio-Culturelle, Droit, Éthique et Santé of the Cnrs of Marseille has just analyzed blood samples belonging to three Neanderthals and a Denisovan: the results of the study, published in the journal PLoS ONE, confirm that the species, at some point, they crossed paths with ours and - more interestingly - that Neanderthals suffered from "low genetic diversity", probably the cause of extinction some 40,000 years ago. The researchers, in particular, found that Neanderthals carried several genetic variants that made them particularly susceptible to a rare form of hemophilia, known as fetal erythroblastosis (HDFN). Rare for the Sapiens, of course, so the incidence is around three out of 100 thousand pregnancies. The analysis also suggests that crossing with our species played a role in the extinction of the Neanderthals themselves, exposing them even more to the risk of developing the disease.

To study the phenomenon, French scientists have examined the genomic sequences (already sequenced previously) of four females (one Denisovan and three Neanderthals, in fact) who lived between 10 and 40 thousand years ago: in this how they identified its blood group and took a closer look at evolutionary history. The analysis confirmed some of the previous hypotheses and suggested new ones: for example, until now it was thought that the blood type of almost all Neanderthals was zero (which would not have been strange: all chimpanzees, for example, have group A and all gorillas type B), while the study showed that these hominids had the same variability (AB0) as we modern humans. Again: from the analysis of the genome it emerged that both Neanderthals and Denisovans have African origins, just like the Sapiens.

Let's come to the most interesting part, that relating to the crossing with our species and extinction of the Neanderthals. "The fact that the genes linked to haemophilia have been detected in individuals separated by four thousand kilometers and 50 thousand years", explains Stephane Mazieres, one of the authors of the work, "suggests that this genetic peculiarity, which leads to the risk of having an anemic fetus , was particularly common among Neanderthals ”. The researchers also found that Neanderthals had a single Rh allele (Rh factor is another element that characterizes blood: it is a protein antigen that can be present - Rh positive - or absent - Rh negative - on the surface of blood cells. rossi) which is lacking in modern humans. With one curious exception: the allele was found on two individuals, an Australian aboriginal and a Papuan, which could represent evidence of a cross between Neanderthals and modern humans before the latter migrated to Southeast Asia. Since mating between people with incompatible Rh factors can increase the likelihood of developing fetal anemia, there is a suspicion that this cross may also have played a role, along with other factors, in the extinction of Neanderthals. . Mazieres concludes: "Overall these elements could have contributed to the progressive weakening of the Neanderthals to the point of extinction, especially if we take into account that at a certain point in their history they had to compete with the Sapiens to 'conquer' the same ecological niche" .

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