Our Neanderthal Immunity
Crossing with Neanderthals has benefited peopleDmitry Tselikov, Compulenta
When the first sapiens left Africa, they were ill-prepared to deal with unfamiliar diseases. Fortunately, interbreeding with other hominids gave them the opportunity to gain genes that not only protected them, but also allowed them to eventually settle all over the planet.
Last year's publication of the Neanderthal genome proved that [even] humans interbred with them. And there is also evidence that Neanderthals entered into romantic relationships with other hominids, including Denisovans. Did interbreeding affect the evolution of our ancestors? Peter Parham from Stanford University (USA) tried to answer this question.
He focused on human leukocyte antigens (HLAs); this family includes about 200 genes that are important for our immune system. It also contains some of the most diverse human genes with hundreds of variants (alleles), which allows our body to respond to a huge number of pathogenic agents and adapt to new ones.
People who left Africa probably had a very limited number of HLA alleles, because they most likely traveled in small groups. Worse, their HLA were adapted only to African diseases.
Parham compared the HLA genes of people from different regions of the world with Neanderthal and Denisovian and found evidence that non-Africans "picked up" new alleles from hominids with whom they interbred.
For example, the HLA-C*0702 allele is common in modern Europeans and Asians, but is absent in Africans. Parham found it in the genome of a Neanderthal and suggested that it had penetrated the genome of Homo sapiens by crossing outside Africa. HLA-A*11 has a similar history: it occurs mainly in Asians, never in Africans, and Parham found it in the Denisovan genome, again suggesting that interbreeding took place outside Africa.
The scientist emphasizes that Neanderthals and Denisovans lived outside Africa for more than 200 thousand years before meeting a reasonable person, and their HLA had to adapt well to local diseases.
Although only 6% of the non-African genome of modern humans has the DNA of other hominids as its source, the proportion of HLA acquired as a result of crossing is much higher. Half of the European HLA alleles came to us from other hominids. In China, this figure rises to 72%, and in New Guinea it exceeds 90%.
In other words, as a person moved to the east, he absorbed more and more of the necessary HLA, whereas, moving to the north, our ancestors faced fewer diseases, according to Chris Stringer from the Natural History Museum in London.
The results of the study were presented at the Royal Society Conference on Human Evolution.
Prepared based on the materials of NewScientist: Breeding with Neanderthals helped humans go global.
Portal "Eternal youth" http://vechnayamolodost.ru20.06.2011