What’s Responsible for the Flynn Effect?

archived from gnxp.com thread regarding eugenics and what’s responsible for the increase in measured human intelligence)

Another possibility is that there are other selection forces, less visible than the ones we reasonably conclude should lead to a decrease in IQ, that provide a counterbalance.

One speculation: IQ is surprisingly strongly correlated with head size. Humans seem to have reached the limits of viable head size already: if female pelvises were further altered to make childbirth easier, women wouldn’t be able to walk, and our brains are already packed in our heads quite efficiently.

Childbirth used to be a major killer of women, even discounting the problems caused by unsanitary doctors. Perhaps in the natural equilibrium, babies with larger heads were more likely to kill themselves and their mothers in childbirth?

Modern medical techniques would then lead to more large-headed children surviving.


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