As it turns out, intelligence in men is correlated with valuing sexual exclusivity. A 2010 study by London School of Economics professor Santoshi Kanazawa established the relationship. More intelligent American boys are more likely to grow up to value sexual exclusivity in early adulthood than less intelligent boys.
So the unwillingness of women to date less intelligent men is rational if they are seeking a mate who values monogamy and sexual exclusivity.
But if intelligence and sexual exclusivity go hand in hand, why are men willing to date less intelligent women? Well, it turns out Santoshi’s study proved something very interesting: for women, there is no statistically significant correlation between intelligence and valuing monogamy. Smarter women are no more likely to value sexual exclusivity than less intelligent women. Or, to flip it around, less intelligent women do not place a lower value on monogamy than more intelligent women.