African pygmy mice: Females are XY ... researchers find out why
Testicles are funny things, and almost all healthy male vertebrates boast two of them. In many mammals, including ourselves, they hang from the body in a scrotum because the valuable sperm they contain are mighty fussy, and mammalian body temperature tends to be just a little too hot for them.
So natural selection kindly began dangling the sperm of males from two sacs between the rear legs, nice work evolution. The diagram below is both hilarious and helpful:.
Where Masturbation and Homosexuality Do Not Exist
Here you can see the gonad size of various primate species in relation to body size. The top row pygmy the males sex the big circle represents their body size, pygmy arrow is the penis and the balls are, well, the balls. No laughing at the gorilla and yes sex, your penis is quite large compared to our primate cousins.
So the size of the testes can tell us a lot of information about the mating system adopted by various species. We have to remember that although in our culture monogamy is often rightly or wrongly seen as the norm, this is far from the case in most other mammalian species.
There are lots of different mating systems: Males of species with promiscuous mating systems such as chimpanzees tend to have the largest testes, and this makes sense freepornxxx of something called sperm competition.