WHY DID THEY DISAPPEAR?
Neanderthals never really went extinct, at least not genetically. Between 20 and 70 per cent of their genome lives on in us, spread among various human populations in Eurasia. In terms of quantity of DNA, there are actually more ‘Neanderthals’ around now than ever. Yet between 40,000 and 35,000 years ago, their fossils disappeared from the record, so the question is: why did we absorb them into our species, and not the other way around?
Proposed theories for our potential superiority have included a broader diet, more efficient tool manufacturing, and even a mastery of symbols and art. But these all look less certain in light of the evidence described in this article, and it’s likely that a number of effects played a role. While Neanderthals had lived through many periods of extreme climate change, the conditions around 55,000 years ago became extraordinarily unstable. If Homo sapiens had even marginal advantages in coping with this instability – perhaps more effective weaponry (allowing us to obtain more food), or extended social networks – then over time this would have built up. On millennial scales, a few extra human babies surviving per year could eventually snowball into a total population replacement, especially if Neanderthals’ genes were being diluted by breeding with us. Their fate wasn’t a dramatic annihilation, but a slow, irreversible assimilation.