Why Human-Neandertal Sex Is Tricky to Prove


A bundle of recent genetic studies have suggested modern humans had sex with Neanderthals thousands of years ago when the two populations roamed the planet alongside each other. However, the bones left behind by the two species don’t bear any obvious traces of interbreeding, and a new study of monkeys in Mexico shows why we shouldn’t expect them to.

Researchers examined blood samples, hair samples and measurements collected from mantled howler monkeys and black howler monkeys that were live-captured and released in Mexico and Guatemala between 1998 and 2008. The two monkey species splintered off from a common ancestor about 3 million years ago; today they live in mostly separate habitats, except for a “hybrid zone” in the state of Tabasco in southeastern Mexico, where they coexist and interbreed.

Through an analysis of genetic markers, from both mitochondrial DNA (the DNA in the cells’ energy-making structures that gets passed down by mothers) and nuclear DNA, the researchers identified 128 hybrid individuals that were likely the product of several generations of interbreeding. Even so, these hybrids shared most of their genome with either one of the two species and were physically indistinguishable from the pure individuals of that species, the team found.

“The implications of these results are that physical features are not always reliable for identifying individuals of hybrid ancestry,” Liliana Cortés-Ortiz, an evolutionary biologist and primatologist at the University of Michigan, said in a statement. “Therefore, it is possible that hybridization has been underestimated in the human fossil record.”

Written By: Megan Gannon
continue to source article at scientificamerican.com


  1. There’s nothing really to prove. If anything it would be trickier to prove that it didn’t happen.

    There’s already evidence of Neanderthal genes in present day human genomes that speaks for itself. Plus there’s evidence that some present day male humans will insert their penises into pretty much any female of any mammalian species that lacks really sharp claws and teeth.

    There’s nothing weird about that – at least from a purely biological perspective. Unusual events don’t have to be very frequent for them to have an impact. Like being homosexual is a sexual preference rather than a sexual determinant. I.e. Not being the same thing as being infertile. So inheriting genes for homosexuality can’t be ruled out.

    That bestiality occurs occasionally in some individuals might be a uniquely defining characteristic of the human species. It’s reasonable for 1 sub-species of Howler monkey to mate with a very similar sub-species of Howler monkey. But it seems fairly unlikely that, excepting humans, males of any other mammal species would attempt to make with completely dissimilar species like goats and rabbits.

    It’s no less weird or disgusting that many adult humans still drink bovine milk. Another peculiarly unique human habit. (Which might possibly be short-lived, pending further research. It might not be prudent to invest heavily in dairy farming in the near future.)

  2. Without actually dredging up the cringe-worthy numbers on bestiality, I think you’ll be surprised at how popular it is among girls, Pete.  I certainly was when my ex sprung that little chestnut on me.

    Not that it isn’t the accepted traditional role of human males to go poking around penis-first wherever they can (thank you concealed ovulation), but taking into account the traditional female role, & attraction cues that slather the female mind in dopamine, it’s not hard to imagine why they might be attracted to a significantly bigger, stronger, more successful hunter/protector hominid species than ourselves.  For examples that persist to modern day, just stroll on down to the local pub on any given night.  The biggest, most muscular, roughest guys always get the girls.

    Perhaps jealousy was the motivation for Thor and his silver hammer slaying the giants in the north.

  3. “more successful hunter/protector hominid species than ourselves” – They are not still around. They couldn’t have been that much more successful.

    Before, whenever I heard about human and Neanderthal interbreeding I would get annoyed, just becuase the way it is usually written about. When they use words like mating or interbreeding, they imply something more. Like there was maybe something romantic going on, or the species were really getting along. Being that neanderthals were probably not that attractive to humans, at least not any of the depictions of them, I find it hard to believe that it wasn’t lots and lots of rape. Maybe Neanderthal sex slaves. From what I know about humans I find it hard to expect anything else.

    But now that I have read your post, I have to add a little to my opinion. I never thought about like that; from the female point of view. So, it was rape, or just wild animal sex. Would it be considered bestiality?

  4. “It’s no less weird or disgusting that many adult humans still drink bovine milk. Another peculiarly unique human habit”
    I’ve never liked milk either. Lactose intolerance is likely a warning flag? 

    SOME humans still drink the urine of camels, cows, goats and horses in the belief they are medicinal as per Islamic teachings. There is at least one ‘clinic’ in the ME promoting it. As recently as 1400 yrs ago they drank the urine of their prophet, too. 

  5. “Human-Neandertal Sex Is Tricky to Prove”
    No it isn’t. Collect a sample of Gary Busey’s DNA and the whole theory will no longer be ambiguous.

  6. I love how the posters on this site always seem to think that they are more knowledgeable than the researchers cited.

  7. I thought the question was always whether or not they could have offspring, and if it would be fertile. That protohumans fooled around was a given. I don’t think it’s comparable to bestiality either. It may have been extra hot and compelling, especially in certain cases. Pheromones’ appeal is based on a certain allowance of genetic dissimilarity they may have fit in.

    Only one way to find out. We gotta bring ’em back.

  8. 1. Ignoring how often it’s mentioned in antiquity, it is not uncommon for girls to have sex with other species even today, from, most commonly, the convenient family dog, to later, size/power fetishization involving ponies and even horses.  Studies have been done over the years, and find numbers as high as 15% (urban) and 30% (rural), +/- (due to the nature of admitting something like this, even anonymously).  Don’t ask me why I’m aware of this.  THE POINT was, while bestiality may have been a possibility, Neanderthals might not have even been considered another species, but simply considered a larger, more muscular, red-headed foreign tribe.  For the species to have coexisted as long as they did, it’s almost unthinkable that there wouldn’t have been some mating, for social or reproductive purposes, just as today.
    2. The neandethals went extinct.  Of all the possible reasons, being ineffective hunters is the opposite of at least two.  With the onset of an ice age, from hunting themselves out of a shrinking food supply to support their enormous dietary requirements, to competing against the increasingly aggressive homosapiens for that same food supply, if there was one thing they were experts at it was hunting.  They survived as hunters a hell of a lot longer than we did.
    3. Hetero, no one is claiming they know more/better info than any given researcher.  Not everything is a competition.  Trying out ways of putting together all the different and often conflicting data from hundreds of discoveries on a subject over the last decade is work.  Riffing on it in a lighthearted speculative way, in an open discussion soon to be forgotten, is fun.  Try it sometime.
    4. Care to elaborate, Kat?

  9. A little reprint of an earlier comment from me to the hybridisation
    The mixup more likely happened like this:
    forget about the local Legends of superpowers and Cryptids and stay
    with the Facts. An “ugly” female wild Child (most probably of
    asian/mongolian origin) stays with the only “Family” it knows and gets
    pregnant despite being very “ugly” and “crazy”.

  10. Pete H said
    “But it seems fairly unlikely that, excepting humans, males of any other mammal species would attempt to make with completely dissimilar species like goats and rabbits.”

    I beg to differ. When I was a kid we owned two Jack Russell terriers; both of them were often to be found attempting to hump my mum’s Flemish Giant rabbits. My current dog, a little Border Collie / Corgi cross, has a stuffed (quite litterally) Donkey (from ‘Shrek’), the stuffing of which I suspect is now more semen than cotton wool.

    Bluebird, you’re a fellow ‘Blues Brothers’ fan, I assume.

  11. Interesting that possibly the only very dissimilar 2 species that are strongly suspected of bestiality might be humans and their domestic dogs. My sister in law once caught one of the adolescent inmates at a borstal having his way with the nanny goat brought in with a petting zoo visit. And I’ve seen various dogs that attempt to rut with people’s legs, regardless of the sex of the other species. (After they’ve been castrated, the dogs that is. And some bitches too.)

Leave a Reply