A new study explains why human males lost the bones in their penis. The study conducted by researchers at the University College of London found that monogamy may have played a role in causing male humans to lose their penis bones.
Other mammals such as bears and gorillas still have their penis bones, also called Baculum.
The study's findings -- which is confusing to read -- explained that mammals need penis bones (baculums) for prolonged penetration while mating frequently with random partners.
The penis bones were critical around 145 million years ago when men needed to maintain their erections longer while fighting off competition from other males during sexual intercourse with females.
The bones helped human males sustain their erections longer in the face of stiff competition (no pun intended).
But as humans evolved about 90 million years ago, men became more civilized and monogamy with a single female (or a harem of women) became the order of the day.
When humans began pairing off and raising families as couples (or a single male with a harem) there was no further need for penis bones since men weren't in fierce competition with other males any longer.
“Our findings suggest that the baculum plays an important role in supporting male reproductive strategies in species where males face high levels of post-copulatory sexual competition,” said Matilda Brindle in a news release. “Prolonging [penetration] helps a male to guard a female from mating with any competitors, increasing his chances of passing on his genetic material.”