Studies of bats and other mammals have found that the average brain size is 36 percent bigger among monogamous males than promiscuous males, researchers say. In bat species with promiscuous females, the male’s body has been shown to use more of its energy to enhance the testes, costing the males the energy needed to further develop their brains. Promiscuity is also associated with big testicles among chimpanzees, whereas dominant gorillas with exclusive access to a harm of females are known to have small testicles.
The implication is that males of some species make a trade-off between brain power and sex appeal. In promiscuous species where there is heightened competition for male sexual success, males are more likely to choose balls over brains compared to non-promiscuous species.
If the results of this research are applicable to the human species, one might dare to speculate, then this could eventually support the stereotypes that associate physical beauty and sexual prowess with low intelligence. Jokes and prejudice surrounding “muscle meatheads” and “blonde bimbos” could get scientific reinforcement. Potentially, stereotypes about breast, penis or ball size could also be put at play. If, say, large penises are supposedly linked to lower intelligence and smaller penises to higher intelligence, then the racial and ethnic aspects of such linkages would become politically and culturally explosive.