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What Two Things Great Dads Have in Common

Go ahead and brag about being a great dad. But know one thing: The rest of us will be thinking about your small balls. A new study has found that though it takes cajones to raise kids, the smaller the cojones, the better.

If that doesn't make a guy seize up a little!

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Science has known for awhile that the higher the testosterone level a man has, the less into his kids he really is, and anthropologists at Emory University think they may have discovered why.

Guys who produced less semen responded, neurologically, in a more nurturing way. Guys who produced higher levels showed more ambivalence toward their own kids. Testicle size is related to how much semen is produced, which is reliant on testosterone. That's how we get the bad dad/big gonad connection.

Could we ever count on Lothario for carpool?

The Emory University researchers came to this conclusion after they put 70 biological fathers in an MRI and measured the size of their brains and the volume of their packages. While in the machine, the fathers were shown images of their kids and researchers noted how much of the nurture area of the brain lit up. These fathers' partners also filled out questionnaires about the men with respect to their parenting. (Judging the size of their sacks was left to standardized measuring instruments.)

The fathers who were described as nurturing—and whose brains lit up when seeing their kids' faces—tended to have smaller nuts. The ballsy ones? They were more likely to be "meh" when it came to stepping up in their role as dad—not so much lighting up in the MRI and less than super-dad reports from partners. (The study included some non-dads to keep the research solid.)

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These conclusions aren't meant to tell us the intimate details about dads working the preschool co-op. But it does shed some light on what anthropologists have long been asking: whether there's a trade-off for men between mating and parenting effort. Could we ever count on Lothario for carpool?

It may take a pair to step up to the role as parent, but to be really good at it, apparently that pair needs to be rather small.

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