I think there are two pieces-- one is that helpless women are perceived as more worth helping than helpless men, as you say. The other piece is that women are perceived as more likely to help children, and helping people who are likely to be helpful is more efficient.
This is interesting, I wonder if there's anything to it: International variation in IQ – the role of parasites (paper) by Christopher Hassall of U. Carleton.
It strikes me as the sort of thing that could be as big an issue as lead in the environment. Raise the sanity waterline: improve health!