Men with longer hair and beards may have smaller testicles than those who struggle to grow facial hair, a study claims.
It found that humans, and more than a hundred other primates, face an evolutionary dilemma when it comes to their genitals.
Teams from the University of Western Australia, who carried out the research, say a male ‘can be well-adorned or well-endowed, but it’s hard to be both’.
Animals can either invest energy attracting females with impressive manes and beards or spend their energy growing larger gonads.
This means hairy human men with a bushy beard and long hair are likely to have smaller testes than their follicly challenged brethren.
For the rest of the world’s primates, this trade-off comes in the shape of having either the bright buttocks of a baboon or the plain features and large testes of plainer primates.
Males have flamboyant physical ornaments – such as beards, manes or capes – or large testes. But, they can never have both, scientists have discovered (stock image)