Men’s aptitude for childcare may be reflected in the size of their testes, according to a study by US scientists.
Researchers found that men with smaller testes were more likely to take charge of children’s bath-time, visits to the doctor, night-time comforting, and other parenting jobs than others who have larger testicles. The same story was borne out by brain scans which showed that men with smaller gonads reacted more strongly to photographs of their own children than did men with larger ones.
The findings are the strongest evidence yet that variations in male anatomy reflect competing evolutionary strategies that can be distilled down to mating as much as possible versus investing more in parenting. Both are effective ways to maximise an animal’s chances of having offspring that continue their lineage.
Jennifer Mascaro, an anthropologist at Emory University in Atlanta, said that while her work revealed a correlation between testes size and parenting, it said nothing about the causes.
She suspects the size of a man’s testes influences how involved he gets in childcare. But the reverse could be equally true: indulging in childcare may make a man’s testes shrink.
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