Why They're on the Outside of the Body
If you've ever been hit in balls, you've probably wondered: Why are these things on the outside? Most people answer that the testicles need to be kept at a temperature two to three degrees lower than body temp in order to function properly but that still isn't a complete explanation. It's hard to say exactly why anything evolved the way it did but researchers at the University of Albany think that balls require this lower temperature to keep sperm dormant for as long as possible. A man's swimmers don't have a long lifespan once they're active, so it's possible that, in ideal conditions, sperm doesn't fully wake up until it's released into the warmth of a woman's vagina.