The Neanderthals procreated with the ancestors of modern humans and left traces of their genetic material.Two studies published in Nature and Science reveal what these traces consist of.
For example, they have allowed to know that the genetic material inherited from Neanderthals has helped the modern human being adapt, but is also involved in diseases such as type 2 diabetes, Crohn's disease, lupus and biliary cirrhosis.
Scientists know that Neanderthals procreated with the ancestors of modern humans and left traces of their genetic material.How the current human being affects this legacy of Neanderthal DNA and how many segments have survived are issues that are not clear.
A study, led by the geneticists of the Harvard School of Medicine (USA) and published in Nature, suggests that the genetic material inherited from the Neanderthals has helped the modern human being adapt - for example, with skin related genes-, but it is also involved in diseases such as type 2 diabetes, Crohn's disease, lupus and biliary cirrhosis.
Likewise, another article from the University of Washington (USA), published simultaneously in Science, has studied in detail how many of these DNA segments have survived.We have more Neanderthal DNA of what was thought so far, it was estimated that the percentage of Neanderthal genetic material that was preserved was between 2% and 4%.
Researchers Benjamin Vernot and Joshua Akey at the University of Washington wanted to go further and study in detail said DNA so they sequenced the full genome of 665 individuals from Europe and Eastern Asia of the genome project."In the first place, we were looking for DNA that came from a species that separated from us 500,000 years ago, but it was introduced into the east Europeans or Asians 50,000 years ago.
Finally, we compare this DNA with the Neanderthal genome, to see how it coincided.More correspond to what we would have expected, which implies that we have done a good job to find Neanderthal DNA, "explains to Sinc Vernot. When comparing the sequences of the archaic and modern genome, their results indicate that although the total amount of the sequenceNeanderthal in any modern human is relatively low, the accumulated amount of the Neanderthal genome that persists through all human beings is 20%.
Neanderthal genome and language The researchers have also found that there are regions of the human chromosome that totally lack neanderthal genome."Chromosome 7, for example, has absolutely none. We do not know for sure why there is no Neanderthal DNA there, but it could be that it was incompatible with the DNA of the modern human. Curiously, the FOXP2 gene, which is known to beAssociated with language skills, it is right in the center of that region, "says Vernot.
Therefore, the current human being has inherited a lot of Neanderthal genes, "something we did not know just five years ago", but many of those genes probably have no different function from current human versions."Some of them seem to have helped us, specifically those involved in the skin," adds Vernot.
At this point, the study published by Nature that analyzes the Neanderthal ancestry, and the problems and advantages of this crossing also coincides.Oasis and deserts of the Neanderthal genome The team of Harvard University studied how Neanderthal DNA influences current human genomes."Now that the probability that a particular genetic variant has emerged from the Neanderthals can be estimated, we can begin to understand how the inherited DNA affects us," says David Reich, a professor of genetics at schoolof Harvard Medicine (HMS) and main author of Nature's article.
Reich and his team - which is also involved Svante Pääbo, of the Max Planck Institute of Evolutionary Anthropology (Germany) - analyzed genetic variants in 846 people of non -African origin, 176 people from sub -Saharan Africa, and a neandertal of 50,000 years ago, whose genome sequence published this same team in 2013.
The most reliable information that researchers have to determine whether or not a genetic variant comes from a Neanderthal is whether that variant appears in some non -African and Neanderthal humans, but not in those of sub -Saharan Africa.
The researchers found that some areas of the modern non -African human genome are rich in Neanderthal DNA, and that this could have been helpful for human survival.Other areas were like ‘deserts’ with a lower average of Neanderthal ancestry.
The finding of these last regions was the "most exciting" for Sriram Sankararaman, HMS and the Broad Institute."This suggests that the introduction of some of these Neanderthal mutations were harmful to non -African human ancestors, and were subsequently eliminated by the action of natural selection," he says.
Infertility and natural selection The team showed that areas with little Neanderthal ancestry tend to group together in two parts of the genome: in the genes that are more active in the testicles and genes on the X chromosome. This pattern has been related in many animals withA phenomenon known as hybrid infertility, which assumes that the offspring of a male of a subspecies and a female of a different one have low or no fertility."This suggests that when the ancestors of human beings met and mixed with the Neanderthals, the two species were on the verge of biological incompatibility," says Reich.
Today's human populations, which can be separated from each other to 100,000 years (such as Western and European Africans), are fully compatible, without any evidence of increased male infertility.On the contrary, the ancient and Neanderthal human populations apparently faced miscegenation challenges after 500,000 years of evolutionary separation.
Risk of diseases The team also measured how Neanderthal DNA present in today's human genomes affects keratin production and the risk of suffering from certain diseases.Experts say that Neanderthal ancestry increases in those genes that affect keratin filaments."This fibrous protein influences the hardness of the skin, hair and nails, and can be beneficial in cold environments, providing thicker isolation," Reich said."It is tempting to think - adds the scientist - that the Neanderthals adapted to the non -African environment and provided this genetic advantage to human beings."
Finally, they also demonstrated that nine known human variants probably came from the Neanderthals.These variants influence diseases related to immune function and also with some behaviors, such as the ability to quit smoking.
To try to improve the results on the human genome, they have also developed, with a team from Great Britain, a test that can detect most of the approximately 100,000 mutations of Neanderthal origin that they have discovered, in people of European descent and are carrying outAn analysis in a biobanco that contains genetic data of half a million British."I hope that this study of place to a better and more systematic understanding of how Neanderthal ancestry affects the variation of modern human features," Sankararaman said.
HeTeam is also studying the genome sequences of the inhabitants of Papua New Guinea, to build a database of the genetic variants that can be compared to the Hominid of Denísova, found in Siberia.