One of the single best predictors of a population’s IQ is the winter temperature of their ancestral environment, with colder ancestral winters predicting higher IQ today. Explaining this correlation, Richard Lynn proposed that higher IQ evolved in colder environments because you had to figure out how how to build shelter, sew clothes, make fire, hunt animals etc.

To me this makes good sense, but critics would point to the cold adapted Neanderthals who are generally considered less intelligent than modern humans, as evidence of the cold not requiring much intelligence. After all the Neanderthals survived the ice age just fine until our own species invaded their territory.

Or did they? New research suggests that our species was not to blame for the Neanderthal extinction.

The Guardian’s science editor Ian Sample writes:

The Neanderthal population was so small at the time modern humans arrived in Europe and the Near East that inbreeding and natural fluctuations in birth rates, death rates and sex ratios could have finished them off, the scientists claim.

But why were their populations so small to begin with? Probably because they weren’t smart enough to adapt to the cold so their death rates remained too high for their population to grow. Despite the fact that their short muscular physiques were exquisitely adapted to the cold per Allen’s rule, it was a problem they never fully solved.