When two genetically distant individuals reproduce, they can pass on traits that give an evolutionary advantage. This phenomenon is called introgression and it would have accelerated our evolution by allowing us to colonize the planet.
Love stories between different human species would have accelerated our Evolution.
Introgression, that is, the transfer of genes between two species by hybridization, can have important effects on Evolution by passing on adaptive traits that can give a species a survival advantage. Several recent studies show that our species also benefited from this phenomenon, in particular through introgression events that occurred between our species (Homo sapiens ) and other closely related species:Neanderthal Man (Homo neanderthalensis ) and Denisova's Man (Homo denisovensis). Being different species, their genome normally diverged a lot from ours and therefore most of their genetic information should have been harmful and therefore eliminated. But, we kept some parts of their information. This phenomenon would have allowed greater adaptation to certain environments.
Introgression would have helped us colonize the globe
When Homo sapiens came out of Africa, he had the opportunity to meet other humans who lived in particular in Europe but also in the Middle East for the Neanderthal Man and in the East and North of Asia for the Denisova man. These "cousins" lived there for millennia and had evolved by adapting to the environmental conditions of these regions.
Introgression, that is, the transfer of genes between two species by hybridization, can have important effects on Evolution by passing on adaptive traits that can give a species a survival advantage. Several recent studies show that our species also benefited from this phenomenon, in particular through introgression events that occurred between our species (Homo sapiens ) and other closely related species:Neanderthal Man (Homo neanderthalensis ) and Denisova's Man (Homo denisovensis). Being different species, their genome normally diverged a lot from ours and therefore most of their genetic information should have been harmful and therefore eliminated. But, we kept some parts of their information. This phenomenon would have allowed greater adaptation to certain environments.
Introgression would have helped us colonize the globe
When Homo sapiens came out of Africa, he had the opportunity to meet other humans who lived in particular in Europe but also in the Middle East for the Neanderthal Man and in the East and North of Asia for the Denisova man. These "cousins" lived there for millennia and had evolved by adapting to the environmental conditions of these regions.
Although they were different species, the sapiens was not yet too far genetically from these other specimens which led to crossbreeding. It is not known how many times this phenomenon has happened, but it is known that between 2 and 7% of the genome of all modern humans originated from these other species (except in Africans). And it seems that at least some of this genetic information gave us an advantage that would have allowed our ancestors to settle in these regions.
For example, according to a 2016 study in the journal Current Biology, Neanderthals passed on to us genetic variants that give us greater immune resistance, as well as skin pigmentation better suited to the lack of sunlight within us. perhaps allowing us to better acclimatize to the cold of Europe and to resist its viruses.
While Denisova Man may have allowed altitude adaptation in Tibet, according to a study published in Nature in 2014. More recently, in July 2019, a study published in the journal PNAS highlighted another trait that our Asian cousins passed down to us:three-rooted molars. This type of molar is very rare in modern humans...except in China and northern Asia and America, where it is present in over 40% of people. "Having an extra root can make those molars stronger “, explains Shara Bailey, a researcher at New York University and author of this study. This can be useful for people who use their teeth as tools:for example, the Inuit, who live in North America, use their teeth to soften the skins of sea lions which they use to make vê ments “, specifies the researcher.
Could intraspecies introgression protect us from disease?
An introgression would also have occurred more recently among human groups of our species but having evolved in very different environmental contexts, according to two recent studies. The first, published in Scientific Reports in 2015 studied the genetic mixing that occurred in Latin America when Europeans and Africans arrived five centuries ago, mixing with Native Americans already there. They highlighted that in their sample (in the city of Medellin in Colombia) the genome of the inhabitants is mainly of European origin (approximately 75% of the genome) or Amerindian (approximately 18%), but that they kept a part of the genome of African origin (about 7% of the genome). This African part of the genome contains genes of the immune system which would give protection against malaria, a disease present in America as well as in Africa. This resistance could have given an advantage and better survival in the region, which could explain why the Colombians of Medellin (a city close to the jungles of the department of Choco) kept this genetic information.
The second study, published in Nature Communications in 2018, looked at the settlement of Madagascar, in the Indian Ocean, where Asian populations mixed with African populations less than 1000 years ago. This mixture resulted in the mixing of their genomes in almost equal parts:40% of Asian origin and 60% of African origin for most of the genome of the current inhabitants of Madagascar. Except for a region of chromosome 1, which would have kept a piece of the African genome almost unmixed with that of the Asian. We would count more than 90% of African origin for this portion which represents in all a quarter of the chromosome. " This region includes a gene associated with resistance to the pathogen Plasmodium vivax, one of the causes of malaria , explains Thierry Letellier, researcher at Inserm and co-author of this study. This would have granted better survivability Asians mixing with Africans, resulting in the mixing of the two genomes. "
These two studies show that phenomena of adaptive introgression have occurred in the recent history of our species. But would it still be possible today? " We are in a time of great genetic mixing, and the settlement of the Indian Ocean can be a very good model to understand what can happen now with globalization ", says Thierry Letellier. While Denis Pierron, lead author of the study, is more nuanced:" The real question is:are there still genetic variants beneficial? If so, then yes, they will surely spread, especially if they can protect against diseases. "