A large-scale reconstruction of thirteen Neanderthal genomes from the Russian part of the Altai Mountains, about 55,000 years old, has increased the total number of fully known Neanderthal genomes to 31. publication in Nature will be released shortly after one of the involved researchers, Svante Pääbo, was awarded the Nobel Prize in Physiology early this month for his pioneering work in the reconstruction of paleo-dna.
What is unique about the new research is that close family relationships between Neanderthals have also been found. Among the eleven Neanderthals from Chagyrskaya Cave, a father and a (young) daughter have been identified, as well as at least two Neanderthals who must have been second-degree relatives, grandparent-grandchild or brother-sister.
The other two genomes come from Russia’s Okladnikov Cave in the Altai Mountains, which form the border region between Russia, Kazakhstan, Mongolia, and China. Neanderthals are evolutionarily close relatives of modern humans and lived in Europe and western Asia between 400,000 and 40,000 years ago.
Similar to mountain gorillas
It is striking how great the genetic relationship between this group is. The research team involved, led by Laurits Skov and Peter Benjamin (Max Planck Institute Leipzig) writes that this degree of kinship is even comparable to that of today’s mountain gorillas in East Africa, of which there are barely a thousand left and therefore strongly are threatened with extinction. That means that the entire population of Neanderthals must also have been small, something that previous studies have also shown. Previously, the total number of Neanderthals living simultaneously in western Eurasia was estimated to be as low as 5,000 to a maximum of 70,000 — far less than the total population of Homo sapiens.
In recent analyses, this small population size is also usually regarded as most important reason before the eventual extinction of the Neanderthals. The ancient idea was that Neanderthals would have died out due to competition with modern humans, who moved into Eurasia from Africa around 50,000 years ago. Last week, that idea was undermined again by a study in Scientific Reports who calculated that in Spain and France Neanderthals and humans must have lived in the same area for only 1,500 to 3,000 years at a time, which offers little evolutionary opportunity for interaction.
Also, according to the genetic models of Skov, Benjamin and their colleagues, the communities in which Neanderthals worked and lived together must have been barely larger than twenty people, at least in the Altai Mountains.
Young women moved away
They also conclude that Neanderthal males must have remained in the group for the most part, while the young females migrated to other groups — a well-known system for preventing inbreeding that also occurs in other primates. The researchers infer this, among other things, from the fact that the mitochondrial DNA (which is inherited through the mother) is much more varied than the DNA of the Y chromosome (which is inherited only in the male line). It is not clear whether the same patrilocal family system existed among Homo sapiens in prehistoric times. In modern humans, there is also less variation in the Y chromosome than in the mitrochondrial DNA, but with larger populations this can also arise if a relatively small number of males are responsible for a large part of the reproduction.
What’s also special is that, because of all the interrelationships, it really seems that the sequenced Neanderthals in the Chagyrskaja cave all lived around the same period.