A Recent Study Explained Why Human Males Don’t Have A Penile Bone

It is an established scientific fact that human males do not have the baculum, which is also known as the penis bone or penile bone. This anatomical truth has baffled people for years. Recently, however, a group of researchers from University College London decided to find out why human males are missing that one bone.

A study published recently in the journal ‘Proceedings of the Royal Society B’ explored the concept of baculum evolvement, along with the theory that humans lost it during the course of evolution as a result of monogamous sexual relationships.

The researchers propose that sometime between 95 to 145 million years ago, the penile bone evolved to provide mammals structural support during copulation and to allow them to have sexual intercourse for extended periods, as lasting longer in sex allows the animals to keep up with the increased sexual competition among male rivals. Hence, being able to last longer favors the males as it hinders other male animals from having sex with and impregnating their chosen female.

A photo of the penile bones of brown bears

Now that we know what the penile bone is for, let’s talk about how the researchers think male humans lost theirs.

According to the researchers, when a couple engages in a monogamous sexual relationship, the postcopulatory competition with other males is decreased. In addition, the duration of sexual intercourse was not considered to be a pragmatically significant factor from an evolutionary viewpoint. But, considering social and cultural factors which were developed later, an extremely short duration of sex was not deemed ideal. The existence of the penis bone in humans has ultimately become non-essential as humans were able to procreate despite its absence.

The study’s lead author, Matilda Brindle, stated:

“Our findings suggest that the baculum plays an important role in supporting male reproductive strategies in species where males face high levels of postcopulatory sexual competition. Prolonging intromission helps a male to guard a female from mating with any competitors, increasing his chances of passing on his genetic material.”

Dr. Kit Opie, co-author of the study, added:

“After the human lineage split from chimpanzees and bonobos and our mating system shifted towards monogamy, probably after 2 million years ago, the evolutionary pressures retaining the baculum likely disappeared. This may have been the final nail in the coffin for the already diminished baculum, which was then lost in ancestral humans.”

Interestingly, chimpanzees and bocobos have extremely short penile bones, measuring only about 6 millimeters in length, and their mating lasts only at an average of 7 and 15 seconds, respectively.