What did it determine? the extinction of Neanderthal man remains one of the most fascinating enigmas of the history of human evolution. A recent study, published in the form of preprint from the University of Zurich and not yet peer-reviewed, that is, yet under review by the scientific community, has identified the possible culprit in one “gene exchange” not very favorable with theHomo sapiensmodern man, occurred when the two species of homo came into contact approximately 45,000-50,000 years ago. According to researchers, the introduction of a variant of the Piezo1 gene (which regulates the metabolism of red blood cells) typical of sapiens, could have caused problems infertility and prenatal survival in Neanderthalsaccelerating the decline of groups already weakened by famines and wars with the emerging Homo sapiens and leading upon their disappearance in the span of a few thousand years.
During evolution Piezo1 differentiated into two variants
Swiss researchers have placed the gene in the dock Piezo1a gene crucial for the correct functioning of red blood cellswhich regulates their affinity for oxygen.
In the course of evolution, this gene would have differentiated into two variants: a “neanderthal” (call V1) and one typical ofHomo sapiens (call V2), different from each other for a single amino acid within a protein of approximately 2,500 residues. A very small difference, but enough to substantially modify the properties of Piezo1. In its form “neanderthal” (V1), in fact, the protein shows a greater affinity for oxygen, a evolutionary advantage which may have helped Neanderthals survive long periods of Freddo And famine of Pleistocene Eurasia, regulating the metabolism and thermoregulation similar to mammals that hibernate. This adaptation no longer proved necessary for modern man, accustomed to milder climates, who thus evolved a variant of Piezo1 (V2) responsible for the formation of different red blood cells, with lower affinity for oxygen.
A “reproductive barrier” behind extinction: the effect of the Piezo1 variant
We know that when modern humans and Neanderthals met, the two populations interbred, “mixing” their genes. For Neanderthals, however, that encounter may have been a real one time bombwhose negative effects manifested themselves slowly, a bit like a small water leak which, drop by drop, over time causes serious structural damage. But how is this possible?
When early Neanderthals (with the V1 gene) and modern humans (with the V2 gene) interbred, both passed on a copy of their gene to their offspring. variant of Piezo1generating a first generation with both gene copiescalled heterozygous (V1V2). Once they returned to their original populations, these hybrid individuals brought with them the modern variantwhich began to slowly spread among small groups of Neanderthals.
It is possible that this very event marked the beginning of decline of the Neanderthalslike the fall of the first piece of a long domino which, one generation after another, slowly led to their definitive decline. During the pregnancyin fact, one mother carrying one copy of the V1 genewith high affinity for oxygen, who was carrying a fetus with two copies of the now widespread “modern” V2 gene, with low affinity, was unable to efficiently transmit oxygen to their young, held like a magnet in the maternal bloodstream, increasing cases of prenatal mortality and infertility.
In modern human populations, a lot more numerous and characterized by a greater genetic mixingthis mechanism did not have major effects, slowly diluting over time until it disappears due to natural selection. For Neanderthals, however, now reduced to small and isolated groupsthe diffusion became rapid and widespread generation after generation, compromising theirs over time reproductive capacity and contributing, in a few thousand years, to their extinction.
Because it is an important discovery
Although it may seem difficult to imagine, for a long time we were not thethe only human species to populate the Earth. Just as today different species of felines coexist, such as the lion and the tiger, in the past our planet was home to multiple human species, including Neanderthal man andHomo sapienswho shared the vast territories of Eurasia for millennia.
The reasons why Homo sapiens whether he became the only species of man alive on Earth remain a subject of debate and are difficult to reconstruct based only on the fossil record. For a long time, the most accepted theories attributed the disappearance of the Neanderthals to climate change, famine and, above all, to violent conflicts with sapiens.
Although it has not yet gone through the review process, this study offers an interesting different perspective, highlighting not only internal clashes and wars, but above all the exchange of genetic material occurred following interbreeding with modern humans. A fateful encounter that had no immediate effects, but which contributed to slowly erode the Neanderthal population until its complete extinction, after about 200,000 years on our planet. The discovery of these mechanisms could not only help to rewrite a fundamental page of human evolution, shedding new light on speciation mechanisms still little studied, but also have important implications for the modern medicinesince some forms of still unexplained infertility could result from processes similar to those identified in the Piezo1 gene
This theory may also clarify why today in our genome very little DNA of Neanderthal origin is present, with the exception of approximately a small percentage 1-2%which represents the only memory of the last meeting with one human species different from ours.
