Smaller testicles, better fathering
Men who have smaller testes are more likely to be better dads to their toddlers, according to a study published in The Proceedings of the National Academy of Sciences.
Researchers from Emory University in Georgia set out to determine why some fathers invested more energy in parenting than others, after prior research showed that children who have a better relationship with their fathers have better social, psychological and educational outcomes.
Previous studies have shown that lower levels of testosterone in men have been linked to increased parental involvement.
But the researchers were interested to see whether testicle volume, more closely linked to sperm count and quality rather than testosterone levels, also played a part.
For the study, the researchers analysed 70 biological fathers who had a child between the ages of one and two, and who were living with the child and its biological mother.
Both the mothers and fathers took part in interviews to determine the father