Not surprising. A lot of people in college have a lot of sex, but a lot have none. It makes sense for a lot of reasons that people who are sexually not precocious would be more intelligent.
I think the result was actually that people on both ends of the bell curve have less sex than people in the middle. More intelligent people tend to be less sexually precocious, but so do less intelligent people.
This sorta makes sense from an assortative-mating POV. People tend to mate with people of roughly equal intelligence. When you get to the outer edge of the bell curve, there're many fewer people of roughly equal intelligence, and you're far less likely to run across them randomly.
Perhaps grad school's real contribution to human science has been the perpetuation of genes for intelligence. Without it and similar institutions, a bright person might never find someone they care enough about to have sex with.
Universities has not existed for more than a few thousand years, so I don't think they could have made much of an impact on the natural selection yet. And I would be surprised if the admittance of female students wasn't quite a recent phenomenon.
