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30 January 2014 07:00
replica of an elderly Neanderthal: Modern humans and Neanderthals had sex with each other, but were genetically not fully compatible
. (Photo: Federico Gambarini / dpa )
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sex with the Neanderthal to modern man has indeed brought its genetic diversity. But also a few medical problems.
The question is now answered: Yes, Neanderthals and modern humans definitely had sex with each other – and probably more than once and in different regions of Europe. Finally, the genetic material of living in Africa today is not human contains about 1.5 to 2.1 percent genetic material that clearly stems from the Neanderthal .
Two recent studies now show that this DNA is not uniformly distributed in the human genome. There are totally free sections and those in which it occurs frequently, for example in genetic sections that structure and type of keratin in human influence ( Nature and Science, online, 2014) .
These proteins are found in the skin and the hair. This may have helped the anatomically modern humans to adapt on their way from Africa to the cooler regions of Europe or Asia, the researchers write. The color of the skin plays about the vitamin D metabolism play a role.
Both studies indicate that the sexual partners of humans and Neanderthals at the time of their confrontations were genetically not fully compatible. This in turn could be the explanation why there are in certain areas of the human genome no Neanderthal traces.
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“That was the price of the crossing,” says population geneticist Joshua Akey of the University of Washington, one of the authors of the Scienc e-study. Harvard researcher David Reich adds: “When humans and Neanderthals mixed, they were at the limit of biological compatibility.”
The researchers found in the studied genomes of a total 1004 people living today regions that are completely free of Neanderthal genetic material. “In these parts of our genome variants Neanderthals were obviously a disadvantage and were quickly selected out of the gene pool of modern humans,” Svante Pääbo, director says at the Max Planck Institute for Evolutionary Anthropology in Leipzig.
The corresponding gene regions for example, lie on the X chromosome, thus affecting the fertility of men. They carry the X chromosome, only one copy and are therefore particularly sensitive to adverse genetic variants. On the X chromosome there is virtually no Neanderthal contribution.
Neanderthal genes are to blame for some diseases
“It’s often the case that in hybrids between closely related species, the male offspring fertility problems,” says Pääbo. The result: They were slow infertile. The new results suggest that we may therefore adopted modern human DNA from Neanderthals more women than men.
The scientists also identified Neanderthal genetic variants in the human genome that may have an impact on many diseases. “These gene variants could weakly interact with the human genome and thus cause disease in us,” says Reich. Maybe they increase the likelihood of developing type 2 diabetes, Crohn’s disease and lupus disease, a rare autoimmune disease. Even an influence on smoking behavior appears to be possible.
variants such as type 2 diabetes were probably initially no effect. The disease occurs only if you have access to an abundance of food, so Pääbo. “From the Neanderthals are both gene variants that protect us, as such, pose an increased risk for certain diseases,” says the researcher.
sex with the Neanderthal to modern man has brought thus both: genetic diversity and a few medical problems
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