Scientists at Emory University have found a potential connection between a man’s testicular proportions and his involvement in raising his children. All over the animal kingdom, males with the largest gonads tend to mate with the most partners, leading to evolutionary theories that such endowment results in more time spent creating offspring than caring for them. The BBC offers details about the study:

The study, in Proceedings of the National Academy of Science, looked at the relationship between testicle size and fatherhood in 70 men who had children between the ages of one and two.

The team at Emory University in Atlanta performed brain scans while the men were shown pictures of their children.

It showed those with smaller testicles tended to have a greater response in the reward area of the brain than those with a larger size.

MRI scans showed a three-fold difference between the volumes of the smallest and largest testicles in the group.

Those at the smaller end of the spectrum were also more likely, according to interviews with the man and the mother, to be more active in parenting duties….

The exact nature of any link is not clear.

The researchers believe the size of the testicles, probably through the hormone testosterone, is affecting behaviour. But it is not clear if the process of having a baby may have some effect on the father.

The researchers acknowledge that there’s more work to be done, for one because the study subjects were all from Atlanta, and so the broader implications of the findings have not yet been determined. Dr. James Rilling, one of the scientists involved in the project, has said that whether or not there’s a correlation between the measurement and paternal commitment, he doesn’t believe “that excuses other men. It just might require more effort for some than others.”

—Posted by Natasha Hakimi

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