Neanderthal Sex: Consent & Interbreeding

With vivid descriptions of Jondalar’s sexual ability and, not least, rough Neanderthal sex, the American author Jean M. Auel stunned the book world. In the first book, “People of the Cave Bear” from 1980, the orphaned Cromagnon girl Ayla is adopted by a group of Neanderthals. But Ayla is seen as different and is therefore forced to have sex with the clan leader’s son. Not enough of that. There were also children.

Back then, in the 1980s, many pundits dismissed the books as unrealistic filth. Not least because of the outlandish idea that we, Homo sapiens, would have been intimate and had children with individuals from a completely different species. Impossible!

All this changed in 2010 when the Swede Svante Pääbo and his colleagues at the Max Planck Institute for Evolutionary Anthropology in Germany were able to show that we humans carry genes that originated with the Neanderthals. So we have had sex with each other, just as Jean M. Auel fantasized about. Between one and three percent of our genetic mass today comes from Neanderthals.

But curiously, these genes are not evenly distributed in the genome. On the contrary, there is a large patch of our DNA where the Neanderthal genes are completely absent, especially on the X chromosome.

According to geneticist Alexander Platt and his colleagues at the University of Pennsylvania in Philadelphia, USA, that can only mean one of two things. Either the genes on the X-chromosome that we inherited from the Neanderthals were so disadvantageous that they have been selected out – or the Neanderthals’ contribution of these genes was smaller, relative to the genes they contributed otherwise. The latter is possible if it was mainly Neanderthals who had sex with women of our own species, since the man would only contribute these genes if the offspring was a girl. Because while women have two X chromosomes, men only have one. In about half of all sexual encounters that resulted in an offspring, the contribution of these genes by the Neanderthal would thus have been zero.

As far as we know the genetic exchange between Homo sapiens and Homo neanderthalensis, as the species is actually called, took place during two separate periods. Partly about 250,000 years ago, partly 45,000 to 49,000 years ago. To find out more, Alexander Platt and his colleagues have now, using advanced statistical methods, analyzed the older period based on a number of genomes (genomes) and then compared how the genome looked in both Homo sapiens and Neanderthals at that time.

The result, which is now presented in the journal Science, shows that the Neanderthal genes on the X chromosome were not selected out in Homo sapiens in the older material.

– According to the researchers, this means that the most likely explanation for these genes not being found on the X chromosome today is that there was selective mating thousands of years later, when Homo sapiens and the Neanderthals began exchanging genes with each other again, which I think is a reasonable interpretation, says Lars Werdelin, professor emeritus of paleontology at the National Museum of Natural History in Stockholm, who read the study.

So Jean M. Auel has once again been proved right?

– Well, you should probably tread a little carefully here. There is nothing in this that says that the Neanderthals abducted and raped these Homo sapiens women, as in the books. In reality, it might have happened once, but it would hardly have been sustainable in the long run. It could just as well have been the case that the Neanderthals were more peaceful and pleasant, which is why the Homo sapiens women preferred them instead. We don’t know that. Ever since Neanderthals were discovered in the 19th century, we have perceived them as more brutal and more primitive, despite the fact that there is no evidence whatsoever for this.

Read more:

Precursor to a written language already in the Stone Age

The genetic makeup reveals our complicated origins

Neanderthal sex gave us loads of bad genes