Not that butt hair is a rare thing: You have it, I have it, the Kardashians have it or they did at one point, anyway. But even in a culture of oversharing, in which we talk openly about nipple piercings and pimple popping , this is one topic that nobody really touches even though we all have questions. While researchers have been able to pinpoint the functions that hair serves on various parts of the body, an explanation as to why we have bum hair is a little more elusive. Zeichner explains. The derm also acknowledges other theories that may explain backdoor fuzz, including the idea that our predecessors required butt hair to help prevent chafing. Another indicator may signal the evolutionary need for butt hair to trap our natural scent.