A new study led by anthropologists at Emory University in Atlanta suggests that bigger isn’t necessarily better, at least when it comes to parenting and the size of a man’s balls.
The study’s lead author, James Rilling, an associate professor of anthropology, psychiatry, and behavioral sciences, said his research team wanted to find out if there’s a link between how involved a parent is compared with their personal anatomy and/or brain function. According to Rilling, “We know children with involved fathers — at least in modern western societies — have better developmental outcomes socially, psychologically, and educationally. Yet, some men choose not to be involved.”
The study, which was recently published in Proceedings of the National Academy of Sciences, was conducted on 70 men between the ages of 21 and 43, who had children between the ages of 1 and 2 and lived with the biological mothers of their children.
The study measured levels of testosterone and interviews were conducted with both mothers and fathers as to the father’s level of parental involvement. Rilling said, "We relied on the mothers' reports because we thought that would be less biased.” They also used MRIs to measure brain activity while the dads viewed photos of their children displaying various expressions (happy, sad, etc.). Finally, they measured the size of the men’s testes using something called a structural MRI, or fMRI.
Researchers concluded from the study that men with smaller testes tended to be more involved parents. Their initial explanation as to why this is relates to the evolutionary trade-off between mating and child-rearing. Larger testes are linked with higher testosterone levels and sperm counts, which correlates with higher promiscuity and marital breakdown and divorce.
Many scientists acknowledge that the reason for parental involvement is a complex area worthy of further study and several in the scientific community take issue with aspects of this particular study.
Assistant professor of urology, gynecology and obstetrics at NYU’s Langone Medical Center, Joseph Alkul, says he feels that the study crosses boundaries by making too many scientific assumptions. "They've assumed a few things and I'm not sure they have the science to back it up," he said.