They may not be related after all. Alex Sobel Fitts says the story is “only demonstrating a correlation between a man’s balls and his parenting abilities, not causation”:

Additionally, the study’s authors aren’t even really talking about “parenting skills,” they’re talking about the engagement of a region of the brain correlated with “nurturing” during an fMRI scan—another form of inquiry laden with journalistic misinterpretation. It might all be in good fun (and a burst of Web-busting unique views for shoving gonads into your lede), except that, as Gary Schwitzer points out in a Health News Review post, “This is the kind of news coverage about a study that results in science and journalism about science losing credibility.”

Well, it was too good to resist. But happy to correct.