More about this on wikipedia: https://en.wikipedia.org/wiki/Variability_hypothesis
IMHO the evidence points to this being a cultural effect that can be changed with policy.
IMHO the evidence points to this being a cultural effect that can be changed with policy.
- Wikipedia cites the study that showed this effect for the brain size (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8675415/)
- IQ is known to be mostly genetic (see e.g. Pinker's "Blank Slate"), so it's unlikely (though not impossible) that the differences in IQ stddev are cultural
- Wikipedia cites another study that found similar effect in birds: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423667/. This kind of difference could evolve due to different reproduction strategies for males and females.