Scientists find species can be ‘well-adorned or well-endowed’ – but not both
A new study suggests doing both takes too much energy
SPECIES with beards may have smaller balls, scientists have claimed.
New findings suggest members of the animal kingdom can be "well-adorned or well-endowed" - but not both.
And they suggest it's because doing both takes too much energy.
A team of researchers in Australia set out to investigate different hallmarks of male virility.
Comparing different species of primates, the scientists showed the smaller on average an animal's testicles were, the more impressive its "sexual ornamentation".
Males win the girls with 'showy' beards
Dr Cyril Grueter from The University of Western Australia said male primates live in a highly competitive environment where they all want the same thing - to father offspring.
"But not all of them can have what they want," he said.
"So how do they 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.
This finding clearly shows that you can be well-adorned or well-endowed, but it’s hard to be both. Why? Trying to do both just takes too much energy
Dr Cyril Grueter from The University of Western Australia
"And if makes cannot keep others off their females, they can win by producing a lot of sperm to swamp those from their rivals."
The team of researchers, which included a group from the University of Zurich, focused on primates because of their "tremendous variation in both testicle size and male ornamentation".
Dr Grueter said some primates had testicles the size of tennis balls, while others were barely larger than a peppercorn.
"We found the same thing with ornamentation - some species sport flamboyant accoutrements such as beards, manes, capes and cheek flanges, and various shades of colour in their faces and fur," he said.
"Others are pretty drab and look more like your Mr Average."
'Showiest males have smallest balls'
Dr Grueter's team made notes on more than 100 primate species.
And for the first time they found those species with beards, extravagant hair dos and ornaments had smaller testicles and therefore lower sperm production.
Simply put, they found the "showiest males have the smallest testes".
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Dr Grueter added: "This finding clearly shows that you can be well-adorned or well-endowed, but it’s hard to be both.
"Why? One of the reasons, the researchers suspect, is that trying to do both just takes too much energy."
The study is published today in the Proceedings of the Royal Society B.
* We'd like to thank factchecker Maarten Schenk (bearded) for rightly pointing out that this study was only in apes and did not apply to human men or their testes as we at first gave the impression of in our headline and article. We're happy to correct.
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