When modern humans have left Africa, a rapid evolution of their red blood cells may have helped them to survive, but it may also have led to the possible disappearance of their red blood cells. Neanderthalreveals a new study.
By sequencing the genome of dozens of people who lived between 120,000 and 20,000 years ago, researchers discovered that Neanderthals had a rare blood group that could have been deadly for their newborns. Their study was published Thursday, January 23, in the journal Scientific relationships.
Humans blood groups are characterized by proteins and sugars – called antigens – present on the surface of red blood cells. Many people know the ABO blood group system, which brings together blood in groups A, B, AB and O. The antigens present on the red blood cells of a person are recognized as safe by the immune systemBut a person with type B blood will have antibodies that attack type A antigens, for example.
Another important antigen is the HR factor, which gives the “positive” and “negative” signs to blood groups. Thus, nowadays, to know which eight possible combinations of blood group and HR factor presents a person is the key to the success of a blood transfusion.
But red blood cells are even more complicated than that: there are hundreds of other less known antigens known to drag on the surface of these cells in modern humans, as well as differences inside cells. These variations in red blood cells are transmitted from generation to generation, a team of researchers from the University of Aix-Marseille in France has decided to look at ancient genomes to better understand the evolutionary history of Neanderthals, Denomist and humans.
In relation: The mystery of the disappearance of Neanderthal chromosome
“Neanderthals have a very rare HR blood group in modern man”, the main author of the study Stéphane MazièresGenerician of the populations in Aix-Marseille University, told Live Science in an email. This HR variant – one type of RHD, another antigen of red blood cells – is not compatible with the variants that the team has found in denials or the first Homo sapiens in their study.
“For any case of inseanguinity of a Neanderthal female with a male Homo sapiens or Denisova,” said Mazières, “there is a high risk of hemolytic disease of the newborn”. The disease can cause jaundice, serious anemiabrain damage and death.
“It could have contributed to the disappearance of the Neanderthal population,” said Mazières.
Experts don’t really know why most modern humans have the HR protein On the surface of their cells, nor why some people lack protein, but a problem can arise if a negative HR person is pregnant with a positive HR fetus. In this scenario, called HR incompatibilityThe pregnant person’s immune system can create antibodies and attack red blood cells from the fetus, causing hemolytic newborn disease.
Today, the treatment of HR incompatibility implies the prenatal administration of a immunoglobulinAn antibody made in the laboratory, which prevents the pregnant person from producing antibodies against the blood of the fetus. But 100,000 years ago, this type of incompatibility of red blood cells would have been impossible to treat.
Mazières and his colleagues have discovered that the variants of the HR gene found today in many people come from the first Homo sapiens ancestors, who seem to have developed them shortly after leaving Africa, perhaps then living on the Persian set. Neanderthals, on the other hand, had HR variants compatible with each other, but which have been largely unchanged in the last 80,000 years of their existence.
While The general isolation of Neanderthals could explain why their red blood cells have not changed much over the years, questions remain regarding the reason why the red blood cells of the first humans have diversified so much and so quickly – over a period of at least 15,000 years .
“My first thought was due to a demographic expansion,” said Mazières. “It is therefore likely that the new environments of Eurasia have contributed to their maintenance over the generations.”
This research on variations in red blood cells are well integrated into archaeological and genetic studies, has suggested Mazières, showing that new genetic lines and new industries of tools in stone tools appeared on the Persian set Between 70,000 and 45,000 years ago. The lack of diversity in the red blood cells of Neanderthals and Denisovians during the same period could indicate a consanguinity and a decline of the population, ultimately leading to the extinction of these groups.