Neanderthals and A wise manthe “modern man”, had regular sex, which then resulted in children. So far, so known. However, according to a new study, this mostly happened between Neanderthal men Sapiens-Women. What caused this is unclear, the research team explains in the specialist magazine “Science”. However, the finding provides a reason why genetic contributions from Neanderthals are strikingly rare in certain regions of the genome of modern humans.
Overall, around two percent of the genome of today’s people of non-African descent can be traced back to Neanderthals.
“Neanderthal deserts”
Table of Contents
The X chromosome is particularly affected by the so-called “Neanderthal deserts”, i.e. areas with almost no genetic material from the human species that became extinct around 40,000 years ago. It is inherited according to gender, as women have two X chromosomes (XX) and men have one X and one Have Y chromosome (XY). Women pass on an X chromosome to each child: sons receive the maternal X (and paternal Y), daughters receive a maternal X plus the paternal Sons only receive their father’s Y.
40 000
Yearsor a few less, it has been since Neanderthals became extinct.
According to the team led by Alexander Platt from the University of Pennsylvania in Philadelphia, the fact that comparatively little Neanderthal DNA on the A wise man had sex. On the X chromosome of Neanderthals, in turn, there is an unexpectedly high proportion of modern human DNA, which can also be interpreted as an indication of such a one-way mating street.
Fossil and present-day genome samples
The team examined DNA traits that entered populations during an earlier phase of mixing between modern humans and Neanderthals. By comparing genetic data from certain Homo sapiens populations without Neanderthal ancestry from sub-Saharan Africa, the researchers identified patterns of gene flow.
Until now it had been assumed that the “Neanderthal deserts” arose as a result of the further evolution of modern humans. The corresponding genes would therefore have simply been lost because they did not bring any advantages. But in the researchers’ opinion, partner choice is the most plausible cause for the patterns found. Only later on did “natural selection”, as Charles Darwin and Alfred Russel Wallace described the process of long-term preference and elimination of certain hereditary traits, have an influence: traits that are harmful to their carrier are sorted out by evolution. This happens because the disadvantaged carriers reproduce less quickly and the corresponding trait disappears from the gene pool of the species in the long term.
Conversely, gene variants are more likely to be retained if they provide a survival advantage for their carrier. Certain Neanderthal genes, for example, apparently improved innate immune defense or influenced fat metabolism and body composition. This in turn was once particularly advantageous in cold climates.
Neanderthal genes with infarction potential
Other Neanderthal gene variants promote greater blood clotting, which once likely helped stop bleeding more quickly. Today, however, it is becoming more noticeable that the risk of thrombosis, infarction and embolism is also increased.
According to research, modern humans began to spread around the world from Africa around 50,000 years ago. Around 47,000 years ago – possibly during a single, long phase of mixing with Neanderthals – it acquired the characteristics that can still be detected in the genomes of all non-Africans today.
Because modern humans came – out of Africa – into areas that Neanderthals had long since settled for more than 250,000 years. Physical was Homo neanderthalensis significantly stronger, as bone analyzes showed. Neanderthal women might therefore have been able to ward off unwanted requests from male modern humans quite well. Sapiens-Women, on the other hand, would probably have been physically inferior to pushy Neanderthal men. And male “protectors” or partners from their own species would also have had a hard time.
But whether something that from today’s perspective would have to be described as rape was really the cause of the suspected one-sided mixing is completely unclear. Other social, demographic or biological explanations are at least equally conceivable. These also include strong Neanderthal men Sapiens-Women may have appeared attractive and the sex was sometimes – or more often – consensual. However, no amount of genetic analysis, no matter how modern, will ever be able to help clarify such questions. (dpa)