Apparently most respectable universities have so many more qualified girls than boys that they favor less qualified boys in their admissions, to maintain a semblance of balance.
Yet at the same time, Caltech does the opposite: goes aggressively out of its way to recruit girls, to try to balance its persistently male student body (a ratio of between 2-to-1 and 7-to-1 over the past 20 years).
Why would there be persistent disparity in opposite directions?
One possibility comes from Darwin’s theory of sexual selection (The Descent of Man, 1871). Males of all species exhibit higher variability in all traits than do females. This is true of all sexually reproduced life, whether animal, plant, vertebrate, invertebrate, etc.
This would reduce the Pomona/Caltech paradox to a statistics problem. Caltech seeks students distinguished by just a few traits, and thus would find most candidates from among the wildest statistical outliers. The wildest single-trait outliers tend to be male, per Darwin.
Pomona, by contrast, seeks students with a balanced set of abilities, so single-trait outliers have no special advantage. Since the odds of a multiple-trait outlier, where those traits are all positive, is vanishingly low, there may not exist enough multiple-trait positive outliers to fill even a tiny fraction of all respectable universities.
Males would then be left with no advantage, and even a possible statistical disadvantage, if variability reduces overall genetic fitness (and there is evidence this is true). That is to say, one might speculate the average male candidate could be inferior to the average female, precisely because the statistical spread of individual abilities is wider in the male, and because the reduced fitness caused by the greater variation brings the average of all abilities in the male down, both in the individual and in the population as a whole.
Add in the proposition that females mature emotionally much earlier than males, and you can see how Pomona and other good schools might logically become persistently female, while Caltech and other “single-trait” schools persistently male.