Which animals have penile bones

Another interesting discovery was that males of species facing high levels of sexual competition for females have longer bacula than those facing lower levels of sexual competition. But what about humans? The average duration from penetration to ejaculation for human males is less than two minutes.

But bonobos only copulate for about 15 seconds at a time and they still have a baculum, even if it is very small about 8mm. So what makes us different? Human males generally have minimal sexual competition as females typically only mate with one male at a time.

Perhaps the adoption of this mating pattern, in addition to our short intromission duration, was the last straw for the baculum. Scientists are only just beginning to piece together the function of this most unusual bone. The picture that seems to be emerging is that, under high levels of sexual competition, bigger is better when it comes to the penis bone. This article was originally published on The Conversation. Read the original article. Already a subscriber?

Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. In "finite element analysis" FEA , a 3D computer model is virtually "crash-tested" in order to calculate how strong the object is. The method is more commonly applied to structures such as bridges or race cars, as a way of predicting their performance without physically damaging the object.

The major benefit of FEA is that the whole 3D shape of the baculum can be incorporated into our estimates of bone strength. Our results suggest that animals breeding for very long durations typically have penis bones that are much stronger than their fast-mating relatives. Previous research, including our own study, has tended to focus heavily on male anatomy, to the exclusion of females. In mammals, less than a quarter of all studies investigating the evolution of genitals have included both sexes.

This bias may partly stem from practical issues—male genitals are often made up of rigid hard parts sitting outside the body, making them easier for scientists to study. But it may also reflect a historic misconception of the female reproductive system as being a "passive" vessel, compared to more "active" male structures.

This means we have potentially overlooked important interactions between the sexes. Thankfully, with the application of new X-ray imaging techniques and computer modelling, our awareness of female genital anatomy is beginning to catch up. We are now extending our study to also include the size and shape of the vaginal tract and to capture the live motion of the genitals during mating, as a more holistic approach to studying animal reproduction.

The tininess of the bone correlates with the very short spell that the male spends mating, in the order of seven seconds. In chimpanzee groups, females mate with all the males, in what appears to be a strategy to reduce the risk of her children being killed by older males. Humans may have lost their penis bones when monogamy emerged as the dominant reproductive strategy during the time of Homo erectus about 1. In monogamous relationships, the male does not need to spend a long time penetrating the female, because she is not likely to be leapt upon by other amorous males.

That, at least, is the theory. This article is more than 4 years old. Penis bones from various mammals. The baculum varies so much in terms of length and whether it is present at all, that it is described as the most diverse bone ever to exist.