Brass Ones

According to a just published study, the size of a man's testicles can predict how involved he'll be in the upbringing of his children.

Researchers at Emory University, US, said those with smaller testicles were more likely to be involved with nappy changing, feeding and bath time. They also found differences in brain scans of fathers looking at images of their child, linked to testicle size. But other factors, such as cultural expectations, also played a role. Levels of promiscuity and testicle size are strongly linked in animals, those with the largest pair tending to mate with more partners. The researchers were investigating an evolutionary theory about trade-offs between investing time and effort in mating or putting that energy into raising children. The idea being that larger testicles would suggest greater commitment to creating more children over raising them.

Only 70 men took part in the study.