"In every final scan we could see a big, full bladder, even though most of the women went to the toilet before they went inside the MRI,” explains Pek with comical astonishment. “We think it might be evolution’s way to force women to urinate after sex. Perhaps our ancestors developed this function to avoid urinary tract infections, but that’s only a hypothesis."

https://www.vice.com/en/article/qvgkzw/the-story-of-the-dutc...

> All amphibians, reptiles, birds, and a few mammals have this orifice, from which they excrete both urine and feces.

> Mating through the cloaca is known as cloacal copulation, commonly referred to as cloacal kiss.

> The cloacal region is also often associated with a secretory organ, the cloacal gland, which has been implicated in the scent-marking behavior of some reptiles, marsupials, amphibians, and monotremes.