A pair of researchers at Temple University has found evidence suggesting that Neandertals have mated and produced offspring with anatomically modern humans several times, not just one, as previous research has suggested. In his article published in the magazine. Ecology of nature and evolution., Fernando Villanea and Joshua Schraiber describe their genetic analysis of people from East Asia and Europe and how they were compared with people from other places. Fabrizio Mafessoni, of the Max Planck Institute for Evolutionary Anthropology, offers an article of News and Opinions about the work carried out by the couple in the same issue of the magazine.
In recent years, scientists have discovered that the first humans to move from Africa encountered Neanderthals living in parts of what is now Europe and East Asia. By comparing Neanderthal DNA with modern humans, the researchers discovered that there was a pair that gave rise to the offspring, which is reflected in the DNA of humans: about 2 percent of the DNA in non-African humans today in day is Neanderthal. In this new effort, researchers have found evidence suggesting that there was more than one such encounter.
Their findings make logical sense, considering that anatomically modern humans and Neanderthals coexisted for approximately 30,000 years. Recent research carried out by other groups had suggested that there had been multiple unions producing offspring: it was found that some people in East Asia had up to 20 percent more Neanderthal DNA than people of strictly European descent. In this new effort, the researchers took a stricter look to discover once and for all whether there were several pairings or only one. They obtained and analyzed data from the 1000 Genomes Project, measuring the amount of Neanderthal DNA in genetic material of volunteers. The first step was to separate the data between people of European and Asian descent. In doing so, it was suggested that both groups had evidence of the first multiple mating events. Then, the researchers studied the rates of the two groups by creating simulations that show results of different numbers of mating events between the two groups. The data from the simulations were entered into an automatic learning algorithm that showed DNA percentage patterns according to the number of crossing events that had occurred.
The researchers concluded that the most likely scenario was that there were multiple cases of crossbreeding between primitive humans in East Asia and in Europe with Neanderthals.
Modern humans inherited the viral defenses of the Neanderthals.
Fabrizio Mafessoni. Encounters with archaic hominids, Ecology of nature and evolution (2018). DOI: 10.1038 / s41559-018-0729-6
Fernando A. Villanea et al. Multiple episodes of interbreeding between Neandertals and modern humans, Ecology of nature and evolution (2018). DOI: 10.1038 / s41559-018-0735-8