Humans are one of the only mammals to not have a penis bone, something that can be found in monkeys (as long as a finger) and whales (up to 10 feet long).
And people have long wondered why. Some have argued the ‘rib’ in the Adam and Eve story is a mistranslation of the euphemism for penis bone, and that its removal from Adam is a creation story to explain this absence.
Scientists, which call the penis bone the baculum, varies so much in terms of length in mammals and primates around the world and is described as the ‘most diverse bone ever to exist’.
Researchers at the University College London found the penis bone evolved in mammals more than 95 million years ago and was present in the first primates that emerged about 50 million years ago.
And from that moment, variation began and the baculum became larger in some animals and smaller in others. And it doesn’t depend on how big you are.
The stump-tailed macaque, weighing at only 10kg, has a very long penis bone at 5cm. It is five times the size of the collarged mangabey, a slightly larger monkey in body but less so in the nether regions.
Head researcher Kit Opie said the penis bone length was longer in males that engaged in ‘prolonged intromission’, essentially penetrating for longer than three minutes. This mating strategy helps the male impregnate the female while keeping her away from competing males.
So basically stamina in the bedroom = longer penis bone.
In chimps, the penis bone is longer than a human fingernail. As they only mate for seven seconds, there is no need for a longer penis bone.
Humans appear to have lost their penis bone when monogamy became the norm. As there is no competition in that immediate moment to reproduce, the male doesn’t need to spend a long time penetrating.
‘We think that is when the human baculum would have disappeared because the mating system changed at that point,’ Opie said, according to The Guardian.
‘This may have been the final nail in the coffin for the already diminished baculum, which was then lost in ancestral humans.’
Details of the research are published in Proceedings of the Royal Society.
‘With the reduced competition for mates, you are less likely to need a baculum,’ he added. ‘Despite what we might want to think, we are actually one of the species that comes in below the three minute cut-off where these things come in handy.’