The Louder The Man, The Smaller His Testicles, Says Science

Researchers from Cambridge University found that our monkey cousins with the loudest calls generally have the smallest balls


Alice Paulse |

Do you have that one friend or know a guy who’s always shouting until he is red in the face or is just really loud? Well, there may be a scientific theory for loud men and you might just end up feeling a little bad for them.

Researchers from Cambridge University have discovered an evolutionary trade-off in Howler monkeys where they linked testicle size and vocal capacities.

Researchers found that our monkey cousins with the loudest calls generally have the smallest balls.

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Unsure what an evolutionary trade-off is? It’s when you’re forced to compensate in developing one trait as a result of underdevelopment of another.

Lead researcher, Jacob Dunn says that, “In evolutionary terms, all males strive to have as many offspring as they can, but when it comes to reproduction you can’t have everything.”

Dunn and his team were the first to observe this type of trade-off which also exists in vocal capacities, using Howler monkeys. According to Medical Daily, “The male Howler monkey uses its impressive voice in order to get the attention of prospective mates.”

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Howler monkey only weighs 6 kg but its cry can be heard up to four kilometres away, making it the loudest animal on the planet. Dunn found a clear relation between the monkey’s ability to have a noisy cry and the size of its testicles.

Monkeys that were with other males tended to have smaller vocal cords but larger testes, whereas male Howler monkeys that lived on their ace had larger vocal cords but small testes.

Thinking this same trade-off could not happen in humans?

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There was a correlation between small testicle size and higher vocal investment that could suggest that men who shout and yell; could be overcompensating for having small testicles and lower reproductive abilities.

This is not the first time that testicles have been brought into the mix and suffered as a result of an evolutionary trade-off. In 2013 study, researchers at the Ludwig Institute for Cancer Research in Oxford UK ‘ theorized that a genetic variant which increases the risk of testicular cancer may have been favoured by evolution because of its ability to help protect those with fair skin from the sun’s harmful UV rays.’

According to Medical Daily, this gene is found in 80 percent of white men but only 24 percent of males from African descent- which could explain why testicular cancer is more common in white men than black men.

Sources: Medical Daily, Current Biology. 2015.

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