Follicly challenged men envious of their mates' beard-growing abilities can take some comfort in the findings from a new study, which reveals a link between hairy men and their testicles.

The University of Western Australia has found humans, along with 100 other primates, can be "well-adorned or well-endowed, but it's hard to be both."

For an animal, their energy is either invested in producing a glorious mane to attract a mate, or growing large gonads.

For the human male, this translates to long hair and an impressive beard, countered by smaller attributes in their nether-regions.

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According to the study's primatologist and co-author, Dr Cyril Grueter, testicle size varies enormously and is linked to a male's appearance.

"Some [primate] species sport flamboyant accoutrements such as beards, manes, capes and cheek flanges, and various shades of colour in their faces and fur," he said.

For an animal, their energy is either invested in producing a glorious mane to attract a mate, or growing large gonads. Photo / Getty Images
For an animal, their energy is either invested in producing a glorious mane to attract a mate, or growing large gonads. Photo / Getty Images

"Others are pretty drab and look more like your Mr Average.

"This finding clearly shows that you can be well-adorned or well-endowed, but it's hard to be both."

The research goes on to explain that, biologically, all males are striving to do the same thing: father offspring.

Grueter says not all of them can have what they want, so they have to find other means to succeed.

"Well, next to simply fighting, they can produce so-called 'badges of status'; showy ornaments that help their bearers control access to females by intimidating other males.

"And if males cannot keep others off their females, they can win by producing a lot of sperm to swamp those from their rivals."