What is the penile bone? Why don’t human beings have?

What is the penile bone? Presumably everyone has a bit of a “bottom”, why don’t human beings have no idea about this, right?

Want to understand strange knowledge, then, the curious little hand starts to slide down the screen.

What is the penile bone?

The penile bone, also known as the rod-shaped bone, is a bone in the penis of an animal. Animals usually hide it in their stomachs, and use a set of muscles to push it into the fleshy part of the penis when needed.

Depending on the animal, the length of the penile bone varies (from 1 millimeter to one meter), and the shape varies widely (from spines, spoons to hooks, etc.). It is therefore described as “the most diverse bone ever.”

The size and shape of the penile bone vary from species to species

Most mammals have penile bones. For example, cats, dogs, mice, and walruses, and even our close relatives, chimpanzees, can’t help but wonder, why don’t humans have them?

To understand why humans do not have penile bones, I must first understand what the penile bones do and why most animals need it.

Wolf skeleton

What is the function of the penile bone?

The most direct function of the penile bone is to play the role of “supporting the backbone” and to ensure the smooth flow of the sperm channel, and then it is a series of benefits that it brings to male animals.

1. Extend mating time

For mammals, prolonged mating can not only increase the chance of conceiving females, but also help males protect females from mating with any rivals and increase the chances of their genetic material transmission.

2. Quick support

For mammals that must mate quickly and repeatedly, the penile bone can provide immediate support. For example, lions in the breeding period need to mate hundreds of times in 5 days, and the penile bone can help them quickly support them.

3. Stimulate female ovulation

In some species, such as lions, lionesses will not ovulate before mating, and ovulation can only be triggered when they are sufficiently stimulated during mating. The presence of the penile bone allows the male lion to stimulate the female lion as much as possible and trigger ovulation to increase the success rate of reproduction.

4. Clean up germ cells

Animal penile bones are very different. For example, honey badger spoon-shaped penile bones can help males-as much as possible to clean up the reproductive cells left in females by the previous male.

It can be seen from the above 4 that the existence of penile bones brings many benefits to animals, so why don’t humans?

Why do humans have no penile bones?

According to a research report published in the Royal Society Report B, “the penile bone evolved for the first time after the separation of placental and non-placental mammals (about 145 million years ago), but it was earlier than the recent common ancestor of primates and carnivores. Before it appeared (about 95 million years ago)”.

This means that the common ancestor of primates and carnivores had penile bones. Therefore, mammals without penile bones, such as humans, must have “lost” it in the process of evolution.

Why is it lost?

1. No need to “fight” at any time

In many mammals, the presence of penile bone means that they can quickly reach the ideal “battle” state. For example, during the estrus period, lions need to mate dozens of times a day. At this time, the existence of the penile bone is very valuable, it can keep the male lion in a good fighting state at any time.

Humans don’t have to fight anytime and anywhere, so losing the penile bone seems not so unexpected.


2. Shorter mating time

Throughout the evolution of primates, possession of penile bones is usually associated with longer mating time (more than 3 minutes). Most importantly, species with longer mating times have longer penile bones than species with shorter mating times. For example, for lemurs, their penile bones are very long if they mate for up to an hour at a time.

If the penile bone is so important in fighting for a mate and prolonging mating, why don’t we have it?

A simple but heart-wrenching answer is that humans are not a species that “mates for a long time”. According to research, the average time for men in that area is less than 2 minutes. This is much lower than many animals with penile bones.

3. The role of monogamy

For mammals with fierce breeding competition, the fiercer the males face in mate selection, the longer their penile bones.

Penile bones are known to be the most common in polygamous animals. Humans tend to be monogamous and can mate throughout the year. Unlike other animals, there is a specific estrus period. Therefore, it is not that confused for humans to gradually evolve and eliminate the penile bone.

Although humans in a certain era adopted a polygamous mating system, this phenomenon is rare, and it is not enough for humans to retain this bone.

Perhaps the adoption of this mating mode, coupled with our short mating time, has become the last straw that crushes the penis bone.

Concluding remarks

Obviously, humans do well without penile bones.

Although the bone itself may be missing, humans do have a similar structure called the “suspensory ligament”.

Like the penile bone, ligaments help keep the urethra open, play the role of “supporting the backbone” and ensure the smooth flow of the sperm duct. Maybe humans have never lost their penile bone, it just becomes something else.