I spent yesterday up in Auckland, running a schol bio preparation day. (And thanks to Mike, Cindy, BEANZ & the Auckland Science Teachers Association) for setting it up.) I do enjoy these sessions (& hopefully the students do too!) as I like the interactions with students & they always ask nice, challenging questions.
Anyway, after we’d finished the main proceedings of the day, someone came up & asked if I’d heard of the ‘killer Neandertal’ hypothesis, & what did I think of it? Was it a good explanation for the evolution of modern humans? The quick answer was, no I hadn’t, so couldn’t really comment – but I’d go & have a look 🙂
I quickly found a website promoting a book by Danny Vendramini. Called Them and Us: how Neanderthal predation created modern humans, the book supposedly provides "new archaeological and genetic evidence to show [Neandertals] weren’t docile omnivores, but savage, cannibalistic carnivores…" – the ‘Neanderthal Predation theory’. (I noticed that the author uses the spelling ‘Neanderthal’ throughout – a bit surprising as the norm these days is to use ‘Neandertal’, after the correct German spelling for the river valley where the type specimen was found.) Given the lack of any real evidence, and of support for this from the wider scientific community, this position would be better described as an hypothesis…
The website goes on to claim that that
Eurasian Neanderthals hunted, killed and cannibalised early humans for 50,000 years in an area of the Middle East known as the Mediterranean Levant. Because the two species were sexually compatible, Eurasian Neanderthals also abducted and raped human females…. this prolonged period of cannibalistic and sexual predation began about 100,000 years ago and that by 50,000 years ago, the human population in the Levant was reduced to as few as 50 individuals.
The death toll from Neanderthal predation generated the selection pressure that transformed the tiny survivor population of early humans into modern humans. This Levantine group became the founding population of all humans living today.
These claims are accompanied by illustrations that make Neandertals appear more akin to gorillas than to modern humans, which is ‘interesting to say the least, given the recent information on genetic similarities between sapiens & neandertalensis. We’re told that the Neandertal Predation ‘theory’ "argues that, like modern nocturnal predators, Neanderthals had slit-shaped pupils to protect them from snow blindness" (thus conflating two ideas – not all nocturnal predators live in snow-covered lands – on the basis of zero evidence, since eyeballs don’t fossilise). And there’s also the statement that Neandertals "had thick body fur and flat primate faces to protect them against the lethal cold."
Now, that last one is just ridiculous. As far as I know there have been no published findings of Neandertal fossils accompanied by evidence of thick body fur. On the other hand, there is tantalising evidence that they may have had the technology to make sewn garments, thus reducing any selection pressure favouring hirsuteness. In addition, Europe was definitely not in a state of constant glaciation during the few hundred thousand years that Neandertals lived there. During interglacial periods temperatures were fairly similar to what they are today – hardly conditions where a thick furry pelt would be selected for (let alone those slit-shaped pupils…).
As for the ‘flat primate faces’ – if you have a look at a gorilla skull you’ll see that the nasal opening is flush with the surface of the facial bones: gorillas do indeed have flat faces & no protruding nose. But a Neandertal skull, like that of a modern human, does have projecting nasal bones & so, by extension, a nose that juts out from the face. In fact, the whole central region of a Neandertal face projects further forward than ours, so it’s hard to see where Vendramini gets the idea of a ‘flat’ face from. He does provide an image of an Neandertal skull, superimposed onto a chimpanzee profile, & claims that the ‘perfect’ fit is evidence that neandertalensis "more closely resembled non-human primates than a modern humans". What’s missing is any recognition that the skull is not in its ‘life’ position but presented at an angle that conveniently fits the point of view being espoused. If Neandertals really did hold their heads at this angle their posture would be distinctly odd, to say the least. Similar techniques were used by some illustrators in the 1800s to support the idea that African negroes were closer to the apes than to Europeans.
And the claims of rape and cannibalism are fairly extraordinary. As the late Carl Sagan said, extraordinary claims require extraordinary proof. So let’s go back to some of those statements. How about the supposedly much-diminished group of Levantine humans becoming "the founding population of all humans living today"? How, exactly, does this fit with the fact that the sapiens populations of Africa were not exposed to supposed Neandertal predation? Or with the colonisation of Australia by Homo sapiens around 60-70,000 years ago?
Or the idea of frequent interspecies rape, of sapiens by neandertalensis? By the way, if all this – the brutish images & tales of rape – isn’t intended to demonise Neandertals, then I’m not sure what would. Frankly it smacks of the way this species was portrayed in the years immediately following its discovery, before palaeoanthropologists began to expose the details of its life – for example, a reconstruction by Frantisek Kupka, based on work by Marcellin Boule. Something of a dehumanising stereotype, in other words.
By the way, there’s an interesting paper by Julia Drell (2000: Neandertals: a history of interpretation) that looks at how portrayals of Neandertal have changed over time, as more evidence has become available – and also as societal attitudes have changed. (NB this may well not be open-access.) Drell also notes that suggestions of cannibalism by Neandertals aren’t new, first appearing in the 1860s. She cites an earlier author as saying that "there is no more universally common way of distancing oneself from other people than to call them cannibals."
In fact, there’s not a lot of evidence of cannibalism in Neandertals – the remains of about 15 individuals that may have been eaten by their conspecifics. And that over the total span of their existence. (I do wonder why they’d turn to cannibalism anyway, given that they were extremely successful hunters of large game going by the butchered remains associated with neandertalensis living sites.) There is no published evidence that supports the contention that Neandertals ever ate non-Neandertal hominins, let alone on the scale that Vendramini suggests. On the other hand, there is evidence of Neolithic sapiens eating each other.
Nor is there evidence of frequent interspecies rape in the gene pool of modern humans. Earlier this year Green et al announced the sequencing of the Neandertal genome, and the results of a comparison of this and the sapiens genome. Their data did suggest a small degree of interspecific hankypanky might have been going on, but not in large quantity. (The data did not support the idea that all modern humans are descended from a rem nant human population in the Levant, as Them and Us would have it; Neandertal genes are notably absent from African populations. Nor does it support the idea of Neandertal predation, despite claims to the contrary on the book’s website.)
The Them and Us website also provides a link to a paper, Neanderthal predation and the bottleneck speciation of modern humans, for the ‘academically minded’. Strangely for an academic paper, the pdf contains no publication details (journal name, volume, & so on) & a Google Scholar search doesn’t throw up any published papers with that name. So it’s a fair bet that this has not been subject to the normal pre-publication process of peer review – something I would expect for an hypothesis that’s supposed to turn our understanding of human evolution on its head…