Neanderthal lineages reconstructed from the modern human genome

This is according to a comparative study of 665 genomes from contemporary European and Asian populations.

The pendulum around the question of whether the Neanderthal man was a separate species of man that became extinct 30 thousand years ago or whether he was nothing more than slightly different external details of modern humans, and they interbreeded, now moves again towards the second option.

Analysis of whole genome sequence data from 665 people from Europe and East Asia shows that more than 20 percent of the Neanderthal genome survives in modern human DNA, carried out as part of the Thousand Genomes Project.

Previous studies have suggested that non-African people may have inherited 1-3% of his or her genome from their Neanderthal ancestors. These ancient DNA sequences vary from person to person, and therefore the analysis of many genomes at the same time is required to determine the proportion of the Neanderthal genome remaining in the study group as a whole. The research covered all the steps from identifying the location of specific parts of Neanderthal DNA in modern humans, to creating the collection of Neanderthal lineages that survive in today's human populations.

Benjamin Vernot and Joshua Aki, from the Department of Genomic Sciences at the University of Washington, reported their findings in an article titled: "Neanderthal gene lineages surviving in the modern human genome" in the January 29 issue of the journal Science Express. Vernot is a graduate student and Aki is a professor.

To test the level of accuracy of their approach, Vernot ran a comparison between suspected remnants of Neanderthal genes found in modern humans and a genome extracted from Neanderthal human bones, in the laboratory of Svante Pabo of the Max Planck Institute for Evolutionary Anthropology in Germany.

"We wanted to know if our predictions, because it is a Neanderthal genome, corresponded to reality" said Aki. The results show that significant amounts of DNA sequences at the population level may come from extinct groups even in the absence of fossil remains after being passed down from generation to generation. According to Aki, there is potential here to discover and characterize ancient humans that interbred with early Homo sapiens. "In the future, I think scientists will only be able to identify DNA from other extinct hominids through modern human genome analysis," Vernot said.

"From our point of view it was a completely computational project", he added, "It is interesting to know how a careful application of the right statistical and computational tools can reveal important aspects of health, biology and human history, but for this a lot of data and good data are required. "

Neanderthals became extinct about 30,000 years ago. They lived in geographical proximity and at the same times when humans anatomically similar to us lived. According to the two, the two groups lived in mutual relations between them and when they mated they gave birth to several fertile offspring, so that parts of the Neanderthal man's DNA were passed on to future generations. In the proposed model, this mixing of DNA could have occurred both before and after the evolutionary divergence of modern, non-African humans from their common ancestors.
It did not take many hybrid offspring to introduce the Neanderthal genes into the first human populations. Still, Aki says, it is not yet known how many Neanderthal ancestors humans living today have. However, the relationship between the two groups was more complex than they thought until now.

"In addition, the analysis of the ancient lineages that survived, raises the possibility that there were adaptation costs for the mixed Neanderthals and humans" said Aki.
"What surprised me the most was that we found evidence of natural selection. Last year, I was willing to bet that a human-Neanderthal hybrid would be similar to a modern human. This is mainly due to the fact that we did not separate from them so long ago on an evolutionary scale."

However, he adds that the Neanderthals were also a possible source of at least some of the genetic variation that allowed their descendants to adapt. Neanderthal DNA sequences are found in regions of the genome associated with the regulation of skin pigmentation. Acquiring these variants by interbreeding with the Neanderthals may have been a quick way that allowed humans to adapt to local conditions.

"We found evidence that the Neanderthal skin genes made Europeans and East Asians more fit from an evolutionary point of view," Vernot said, "and that other Neanderthal genes did not fit with the rest of the modern human genome, and therefore did not survive in human populations today. "

According to the scientists, the "free fossil" method of archaic genome sequences holds promise in revealing aspects of the evolution of extinct humans and the genetics of their typical populations. In addition, the method may provide insights into the way in which this hybridization affected the diversity of the human population.

In addition, studies of this type can also help researchers locate genetic changes not found in any other species, and learn whether these changes helped give early humans the traits unique to the human species.

To the announcement of the researchers on the website of the University of Washington

More of the topic in Hayadan:

• Archaeologists have rediscovered the lost home of the last Neanderthals in Western Europe
• A 120-year-old cancerous tumor was found in Neanderthal bones
• There were three subgroups of Neanderthals
• First evidence of regular use of fire in Kesem Cave from 300 thousand years ago