Although an erection might be called a boner, humans, unlike most mammals, don't have a penis bone. It's been a mystery to many why we deviate from our animal relatives below the belt, but thanks to new research by University College London, scientists have offered the general public some answers to this penile puzzle.
Despite its ability to get rock hard, the human penis is made up of relatively soft parts. In the very center is the urethra, which is surrounded by the corpus spongiosum, a tube of spongy tissue that runs along the front and fills with blood to hoist the mast, so to speak. The corpus cavernosum serves the same function, but runs along the sides of the shaft. In animals such as chimps and gorillas, however, the penis bone — called a baculum — is located above the urethra, and helps the penis maintain maximum stiffness, amongst other functions.
Penis bones vary in size and shape from animal to animal, but they all play a part in procreation. So what were the evolutionary pressures that caused the human penis bone to evolve out of existence? The ways humans do it has a lot to do with it.
Here are five facts about baculums:
1. Human Sex Doesn't Last Long Enough To Need One
Although we like to sing songs about sexing all night until the break of dawn, that's actually a rarity amongst our species. Matilda Brindle, one of the study authors of "Postcopulatory sexual selection influences baculum evolution in primates and carnivores" explains in The Guardian: "The human intromission duration tends to be below two minutes, which most people wouldn’t expect." Because it's so short, there need not be a bone to keep up our boners, so to speak. Lemurs, on the other hand, have an impressively long baculum, and tend to do it for up to an hour at a time.
2. Human Sex Isn't Competitive Enough To Need One
It can definitely seem like there's a significant amount of competition out there when trying to mate, but humans have the option of doing so year round, unlike some animals that only duke it out for sex during certain seasons. This is another reason, according to researchers, that the penis bone became less of a necessity.
3. Human Sex Isn't Polyamorous Enough To Need One
As much as polyamory and consensual non-monogamy have been on the rise recently, humans are still more monogamous than most species. Study author Brindle notes that our propensity for one-on-one is "probably the thing that finally got rid of our baculum." Whereas chimpanzee males and females mate with as many members of the opposite sex as they can, humans, for the most part, do not.
4. A Baculum Serves Multiple Functions
Although the most obvious function the baculum serves is to keep a penis hard, according to National Geographic, there are additional possibilities. Some scientists say the penis bone helps carry more sperm into the female, while others say it carries the sperm farther. It's also possible that the bone itself can trigger ovulation in the female of the species.
5. The Baculum Is Thought To Have Magic Powers
Once a baculum has served its animal master in life, it might end up becoming part of a talisman in death. In some folk magic traditions such as hoodoo, the penis bone is thought to bring good luck. Raccoon penis bones in particular are used in a variety of practices — and they became a popular accessory on celebrities in the early aughts. So even if humans aren't given their own baculum through biology, we still find ways to get a hold of one in the end.
Images: Andrew Zaeh for Bustle; Giphy
