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  • Writer's pictureAmos Gdalyahu

Let's Go Down To The Barebones

Updated: May 12

Why don't men have a bone in their penis? This question derives from the fact that many animals have a bone in the penis and, by the way, also in the clitoris (!). The bone in the penis is called the Baculum (1), and the bone in the clitoris is called the Os-clitoris (2). All our primate relatives have one, while we humans, as is well known, do not.

Why is it good to have a bone in the penis or in the clitoris?

In fact, this isn't even a question for many men with erectile dysfunction... They would be happy if evolution had thrown them a bone. The thing is, an erection without a bone requires a complex mechanism of increasing blood flow to the penis during sexual arousal, accumulation of blood in the organ at relatively high pressure, and finally, blood drainage. This is a process that involves nervous control over muscle cells around blood vessels and an anatomical structure that causes blood to be trapped in the organ. (See a previous post here). The problem, of course, is that the more complex a process, the higher the chance of malfunctions. With a bone, it's much simpler.

Beside simplicity, it is found that many animals with a large penis-bone live in groups, and their sexual act lasts particularly long. It is thought that the reason for the long duration is that in a group, there is a lot of competition for an ovulating female, and the male tries to prevent other males from mating with her as long as she is ovulating, thus 'holding the place' for a long time. A bone suits an erection for such a long duration.

So a large penis bone is found in animals that mate only during the female's ovulation period, under conditions of intense competition between the males, and for a long time. This requires some external sign that tells males the female is ovulating. In humans, as is well known, there is no such sign, and humans have sex more frequently than the ovulation frequency and for a shorter duration.

So far, I have talked about the advantages of having a bone in the penis, what about the advantage of having a bone in the clitoris? Well, actually, no advantage was found. It may be that a bone in the clitoris is like nipples in men: a result of developmental similarity of the sexes when it has a benefit for only one sex. Accordingly, in species where there is a bone in the clitoris, there is a lot of variation in its size, and not all females even have one. For example, in X-ray imaging, about 3% of female dogs (bitches) are found to have a clitoral bone, and researchers concluded - “This study has shown that an os-clitoridis can be present in bitches assumed to be reproductively normal” (3). By the way, this is the most obscure article there is, but here I found you an article about the clitoris of bitches.

Some readers (men and women alike!) might think it would have been nice to have a bone in the penis, but apart from the discomfort - for example, running like that - there is another problem with a bone in the penis: it can break, and indeed in animals it happens. Ouch.

So why don't humans have it?

It’s impossible to really know, but there are several theories -

One, it is possible that humans are too smart. Humans understood that to prevent their competitors from mating, they could break their penis. If a man was born by chance without a bone in his penis, he had an advantage because it was not possible to prevent him from mating (4).

Second theory, it is possible that the complexity of the erection process makes an erection without a bone a sign of good health (5). That is, a man with health problems will not be able to achieve an erection. Indeed, erectile dysfunction is a precursor sign to other health problems. Women can filter out unhealthy men in this way to get pregnant from a healthy man so their offspring will be healthy and so that the dad could help in upbringing them.

Third theory, the rib that God took from Adam to create Eve was actually the penis bone, and since then, humans do not have a bone in the penis. Maybe... Readers are invited to choose the explanation that they find most plausible.

In any case, although primates do have a bone, it is small and seems that the bone has become smaller and disappeared entirely in humans. However, the medical literature describes one case of a reappearance of the bone: a boy born in 1964 in the USA had a bone in his penis (6). It prevented him from urinating while standing (probably because of the angle of the bone), and at age 5, the bone was removed in surgery (for those interested in details: the length of the bone was 2.5 cm).

Let's continue with the subject of length, the world record belongs to the walrus, whose penis-bone reaches about 60 cm! (Wow!) In its female counterpart, the clitoral bone is about 2 cm.

Did John Lennon think about it when he sang “I’m the walrus”?

Thank you for reading, this was a hard subject.

In the picture (from Wikipedia ref.#1), the penis bone of a walrus. It is not only long but also thick so it won't break.

and a walrus (image by vecstock freepik)


1. Wikipedia on baculum:

3. Os clitoridis presence on radiographs submitted for coxofemoral dysplasia evaluations

Michelle Kutzler, G. Gregory Keller, Fran Smith, (2013), Clinical Theriogenology

4. The missing human baculum: a victim of conspecific aggression and budding self-awareness? Jakovlić, Ivan, (2021), Mammal Review

5. The selfish gene, Richard Dawkins (2006, p. 309)

6. Congenital os Penis, Champion, Richard H, Wegrzyn, John. (1964), Journal of Urology

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