"We like having power-equal relationships, because we think it more moral, because we encourage sexual partners to be companions and friends rather than sticking to separate social spheres, and because it has become more valuable to have a partner who can help you socially and earn money than to have a fertile one."
Who is "we"? Power and sex have deep links. Sexual attraction often does not follow modern egalitarian norms, or indeed norms at any part of history (this is famously exploited in romantic plots in books/movies/tv shows, and similarly frequently observed in practice). Sexuality is ancient, predates morality (and social animals in general), and is often amoral and even cruel. Sex and political correctness do not really overlap.
"Older women's interest would be to encourage woman-boy relationships rather than discourage man-girl ones."
This statement assumes genders experience physical attraction in "symmetric" ways. It is not obvious why this should be so, and there is some evidence it is not.
Why don’t men go for younger women? That’s not quite accurate, because they do, but we seem to have a cultural norm against girls who have recently exited puberty, even though they are highly fertile. Some time in the last few hundred years, we reached a cultural norm that as a man gets older, it’s increasingly less appropriate for him to be with a sixteen year old. That’s not long enough to override thousands of years of evolution, so what could have contributed to it?
The best solution I’ve heard started by looking at who benefits from this norm [older women] and wondering whether they could have contributed to it. After all, the strength of this norm has been increased in the last sixty years or so, which coincides with the period in which women’s power has increased.
One alternative I heard recently is that it doesn’t make sense biologically to go for women who are recently post-pubescent, as they don’t make the best mothers. Instead, a slightly older woman [mid-twenties] makes sense to be the best mother. This is perfectly plausible.
Another, less plausible, suggestion I’ve heard is that it’s to do with mental capacity. I find this unconvincing because we have few objections to a high-status man dating a beautiful but low-intellect woman.
Thoughts?