[smoll]

> I wonder what exactly is meant there. Is he speculating that a larger brain directly provides better parenting ability? Or that perhaps generations ago a family with a useless gene that causes large brains also happened to have another unrelated gene that gave them better parenting abilities, and thus both genes ended up being reproduced a lot?

My guess is something closer to the former, that the two sets of genes are linked https://en.m.wikipedia.org/wiki/Genetic_linkage and there’s a direct causal relationship between the two. Therefore, it’s actually the “better parental ability” trait is the one that produces the positive result and not the “bigger brain” trait. So yes, adopted children could help falsify this hypothesis.