Our bodies are weird, as the farts that half of you will inadvertently release while reading this can attest. And though we all live in one, there's a lot about our bodies that we still don't understand. Why do we faint at the sight of blood? Why do teenagers break out into a pimply mess just when they've reached the point where they want to attract the opposite sex instead of making them run away in disgust?
Usually, the answer is that society evolves faster than biology, and quirks that helped us survive in the woolly mammoth days are now a pain in the ass. For example ...
Acne Might Have Kept You A Virgin Until You Were Strong Enough To Raise Kids
Acne doesn't seem to serve any purpose beyond making the lives of teenagers even more miserable. A bad case of it pretty much guarantees that you have plenty of spare time to do your math homework, because no one wants to date someone who looks like an alien life form is slowly taking over their face. And despite your mom insisting that you were still beautiful, that may have been nature working exactly as intended.
Nature is a dick.
According to one theory, there was a time when a pimply mess on your face kept the opposite sex away while you went through the process of becoming a finely-tuned reproductive machine. Adolescence produces an interest in sex, but it doesn't magically provide you with the experience and maturity required to raise a child (or to defend it from wolves, if we're thinking in terms of evolution here).
So acne provided a buffer period, giving sexually-motivated adolescents time to learn how to be responsible. Because while bad parenting today merely means a visit from the government and/or a reality show contract, historically it meant dead children, which was a huge waste of resources -- and also prevented people from passing on their genes. Destroying the topography of a teen's face may have been nature's way of buying them time to realize they wouldn't make it as a wandering cave artist, get their hunting and gathering act together, and give their eventual offspring a better chance of survival.
Nature could have simply delayed sexual maturity, but nature likes watching you masturbate.