The hominin lineages of Neanderthals and Denisovans emerged around 300,000 years ago, interbreeding with humans on several occasions. We're still not sure exactly what they were like and what went wrong for them, but new studies are constantly shedding new light on them.
For instance, it was thought that Neanderthals all had an O blood type -- just like chimps are all type A and gorillas are all type B. But according to a new study carried out by researchers from Marseille, France, that's not really the case.
Both groups seem to display the full range of ABO blood type variability observed in modern humans. Furthermore, the researchers found alleles (variant forms of genes) suggesting that Neanderthals and Denisovans also emerged from Africa, just like modern humans.
The team examined previously sequenced genomes of one Denisovan and three Neanderthal females who lived some 100,000-40,000 years ago. There are around 40 known blood group systems, but the team focused on the seven usually considered for blood transfusion purposes, the most common of which are the ABO. The findings lend new support for some existing theories but also shed new light on these populations.
In addition to the blood type distribution, Neanderthals also seem to harbor a unique Rh allele which is only present in one Aboriginal Australian population and another population in Papua New Guinea -- and is absent in the rest of the humans on the globe. This could mean that Neanderthals and some of the human ancestors of these two populations interbred.
The findings also suggest that these ancient hominins exhibited little genetic diversity. This would have made them vulnerable to several genetic disorders. While this is not conclusive evidence, it strengthens the idea that low diversity contributed (maybe decisively) to the demise of the Neanderthals, and potentially the Denisovans as well -- the group is far less known and more mysterious.
Ultimately, although physical evidence remains thin, studies such as this one can help us better understand these ancient groups nad how we relate to them. The more researchers look into it, the more it seems that they were similar to humans in more than one way -- which is probably also why the groups interbred quite a bit.
The study has been published in