Smaller Balls, Better Dads

Ball shrinking in progress (Photo: amidala76/Shutterstock)

Ladies, looking for a mate to sire your offsprings? If yes, know this: size matters. But when it comes to caring for infants - think smaller, not larger. See, when it comes to nurture, it turns out that men with smaller balls are better dads.

In a study published in the Proceedings of the National Academy of Sciences (or PNAS as it's lovingly called by the science types - go ahead and laugh, it's okay), researchers at Emory University showed that dads with smaller gonads are more likely to be nurturing to their infant children.

How did the researchers find out? They used MRI to measure the gonads of 70 biological fathers (age 21 to 43), studied the dads for activity in the brain area believed to be involved in parental motivation, and interviewed mothers about their involvement in childrearing.

The study results showed that both testosterone level and testes size are inversely correlated with paternal parenting involvement. Basically, the higher the testosterone - and since this hormone governs the size of the gonads - the larger the testes, the less likely the men would become involved fathers.

Emory anthropologists James Rilling noted that life history theory, which posits that organisms evolve strategies to produce the largest possible number of surviving offspring, suggest that fathers allocate resources toward either mating or parenting. "Our data suggest that the biology of human males reflects a trade-off between mating and parenting ... previous studies have shown that children with more involved fathers have better social, psychological and educational outcomes."

But which come first? Do smaller balls make men better parents, or does involved parenthood shrink men's balls? "We’re assuming that testes size drives how involved the fathers are," Rilling noted, "but it could also be that when men become more involved as caregivers, their testes shrink. Environmental influences can change biology. We know, for instance, that testosterone levels go down when men become involved fathers."