Scientists have found a link between the size of a dad's testicles and his role in bringing up his children.
Researchers at Emory University in America found that fathers with with smaller testicles were more likely to be involved with nappy changing, feeding and bath time.
The boffins were examining the theory of trade-offs between investing time and effort into mating, or putting energy into raising children – the idea being that those blessed with bigger testicles would be more into making babies than caring for them.
The study looked at the relationship between testicle size and fatherhood in 70 men who had children between the ages of one and two. The research team carried out brain scans on the men while they looked at pictures of their children.
The dads with smaller balls tended to show a greater response in the reward area of the brain when shown images of their children, than those with bigger testicles did.
Overall, the MRI scans showed a three-fold difference between the volumes of the smallest and largest testicles in the group.
One of the report's authors, Dr James Rilling, said the the results show that some men are more naturally inclined to care-giving than others, but added that he didn't think that having large balls excused men from childcare duties.
"It just might require more effort for some than others," he said.
What do you think? Another load of boffin balls?
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