The Louder The Monkey, The Smaller Its Balls, Study Finds
Comparisons are constantly drawn between monkeys and humans, not least because of our shared evolutionary traits.
For this latest study into the lives of monkeys, we'll compare them to a very specific type of human - namely, the racing-driver-wannabe bellend who lives annoyingly near you.
Yes, the one with the massive exhausts on their car, that scream through the streets late at night. The common phrase for this type of person is often: 'Well, they are compensating for something much smaller'.
Howler monkeys are similar in the fact they are the loudest animals on Earth, capable of shouting at volumes of 140 decibels.
For comparison, that's similar to the sound on an aircraft carrier deck, louder than a military jet taking off from 50ft away and harsher than a balloon popping.
For the male howler monkeys, they can use this to their advantage, using their roar to advertise their sexual fitness, and attracting female attention.
But whereas their shouting may be something to be proud of, it comes with a downside: the louder the monkey, the smaller its balls.
A team of researchers form Cambridge University came to this conclusion by comparing the size of dozens of monkey testicles with the size of the hyoid bones in their voice boxes.
The results showed a negative correlation between the size of one and the size of the other.
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Anthropologist Leslie Knapp, a senior author of the study, said: "We found that males with larger hyoids, who can make lower-pitch vocalizations, have smaller testes and live in single-male groups with a harem of a few females.
"Males with smaller hyoids live in multimale groups and have larger testes."
The study, one of the first of its kind, can help explain why the social structure of howler monkeys can vary.
Louder male monkeys, with small balls, are likely to have a collection of females with whom they has exclusive access too when breeding.
Bigger-balled monkeys however end up in groups, with sexual partners often shared. Not only are they swinging from tree to tree, but clearly swinging in other areas as well.
It has led to two sexual strategies being developed: 'calls versus balls'. Loud monkeys need their exclusive access so to not fear rivalled by their big-balled counterparts who are more likely to fertilise females due to a higher sperm count.
Science tells us that humans evolved from monkeys, so based on this research you'd suggest those speeding muppets in their souped-up cars probably need to reassess their bragging.
Featured Image Credit: PA