Neanderthal men were short, stocky and powerful – and our female ancestors seemed to be into it, according to a new study.
It’s a well–known fact that ancient humans and Neanderthals had sex, as many people today carry elements of Neanderthal DNA.
But how this intimate chapter of our evolution played out has remained elusive – until now.
Experts have discovered that when these two ancient species had relations, the pairings were mostly between male Neanderthals and female homo sapiens.
The finding adds to our understanding of interbreeding between these distinct groups, which took place between 45,000 to 50,000 years ago, scientists say.
‘Roughly 600,000 years ago, the ancestors of anatomically modern humans and their closest–related species, the Neanderthals, diverged, forming two distinct groups,’ Sarah Tishkoff, Professor of Genetics and Biology at the University of Pennsylvania, said.
‘Our ancestors evolved in Africa, while the ancestors of Neanderthals evolved in and adapted to life in Eurasia.
‘But that separation was far from permanent.’
An AI reconstruction of a mixed Neanderthal–Homo sapiens family. Here, the father is depicted as Neanderthal while the mother is Homo sapien
For their study, the team analysed Neanderthal and modern human genomes.
They found that in modern humans, genetic contributions from Neanderthals are unusually rare on the X chromosome.
Since females carry two X chromosomes and males carry only one, this suggests that little DNA from female Neanderthals ever entered the human gene pool.
The researchers also discovered that Neanderthals had more human DNA on their X chromosomes than anywhere else in their genomes.
This genetic pattern also boosts the theory that there was preferential mating between Neanderthal males and human females.
The findings, published in the journal Science, challenge an old assumption that natural selection is what weeded out ‘toxic’ Neanderthal genes on the X chromosome.
‘Along our X chromosomes, we have these missing swaths of Neanderthal DNA we call “Neanderthal deserts”, said Dr Alexander Platt, a senior research scientist in the Tishkoff Lab.
‘For years, we just assumed these deserts existed because certain Neanderthal genes were biologically “toxic” to humans—as tends to be the case when species diverge—so we thought the genes may have caused health problems and were likely purged by natural selection.’
The discovery provides a more social interpretation of the genetic data, the team said.
‘Mating preferences provided the simplest explanation,’ Dr Platt added.
He explained interbreeding may have been strongly sex biased ‘due to the right combination of being more attractive or simply less repulsive.’
When asked how Neanderthals and humans may have communicated, Dr Platt said: ‘I’m not sure communication is necessary to know what the heart wants. Or to understand who is unappealing. Or maybe tolerable.
‘The data also do not give any insight into whose opinion mattered on the subject, or which of the parties were making the choices.’
He added: ‘We knew that there were at least several times when the two groups met and interbred.
‘What we’re learning now is that that process of interbreeding may have been selective, and that men and women did not participate in it in exactly the same way.’
The team said that now the ‘who’ and ‘how’ of these ancient trusts is established, they are now turning their attention to the ‘why’.
Recent research also found evidence that ancient humans and Neanderthals snogged 50,000 years ago.
For the study, the researchers collected data from the scientific literature on the modern primate species that have been observed kissing, including chimps, bonobos and orangutans.
The experts defined kissing as non–aggressive, mouth–to–mouth contact that does not involve the transfer of food. Using a statistical approach called Bayesian modelling to simulate different evolution scenarios, they found that Neanderthals likely engaged in kissing during their existence.
This finding adds to a previous study that discovered humans and Neanderthals shared oral microbes via saliva transfer.
Combined with evidence of interbreeding, it strongly suggests that humans and Neanderthals kissed one another during their sexual interactions.
‘We of course assume that mating was consensual,’ Paul Pettitt, professor of archaeology at the University of Durham, previously told the Daily Mail.
‘But a sad fact of the ancient world may suggest that this was far from the truth and perhaps one ‘partner’ had little choice in the matter.
‘Thus, in the rough and tumble of the prehistoric world perhaps mating just occurred – impromptu, with little thought or intention. If it was consensual then we can certainly assume there was foreplay – even sensual kissing and cuddling.’
WHAT KILLED OFF THE NEANDERTHALS?
The first Homo sapiens reached Europe around 43,000 years ago, replacing the Neanderthals there approximately 3,000 years later.
There are many theories as to what drove the downfall of the Neanderthals.
Experts have suggested that early humans may have carried tropical diseases with them from Africa that wiped out their ape-like cousins.
The first Homo sapiens reached Europe around 43,000 years ago, replacing the Neanderthals (model pictured) there approximately 3,000 years later
Others claim that plummeting temperatures due to climate change wiped out the Neanderthals.
The predominant theory is that early humans killed off the species through competition for food and habitat.
Homo sapiens’ superior brain power and hunting techniques meant the Neanderthals couldn’t compete.
Based on scans of Neanderthal skulls, a new theory suggests the heavy-browed hominids lacked key human brain regions vital for memory, thinking and communication skills.
That would have affected their social and cognitive abilities – and could have killed them off as they were unable to adapt to climate change.
