It's interesting how women naturally revert to the mean, by reproductive success, more than men do.

There seems to be some upper-ceiling on positive traits in human females, such as intelligence, height, slimness, career-orientation, athleticism, etc. at which point female fertility becomes depressed, and the overall population slowly evens out, again. This is happening within native ethnicities, in wealthy countries (now, even the Dutch!), and doesn't seem to merely be a result of migration.