Why Do Humans Have Butt Hair?


Ben Taub

Freelance Writer

clockNov 2 2021, 12:34 UTC
Butt cracks

Butt hair is something of a mystery. Image credit: ThomasDeco/

Despite being the least hirsute hominin, humans have retained a fair amount of hair in our most intimate regions, including our butt cracks. However, while the hair on our heads, in our armpits, and around our sexy bits serves a number of obvious functions, scientists still don’t have a definitive explanation for our bewhiskered backsides.

To try and shed some light on the mystery, SciShow set their crack team of investigators on the case, revealing their findings in a video that has already been viewed by over 4 million people who clearly feel the need to understand why they possess hair on their rump. Unfortunately, however, very little scientific research exists on the subject, which means it’s only possible to speculate on the purpose of our tufted tail-ends.


One theory states that we have butt hair for no reason other than that there is no major evolutionary pressure against it. In other words, the presence of hair around the anus doesn’t appear to impede our chances of passing on our genes, and having less fuzz on one’s bum doesn’t, therefore, bring any reproductive advantages.

According to this hypothesis, butt hair does not have any evolutionary purpose but exists simply because there has never been any need for us to lose it. This is good news for anyone who may be a little embarrassed about their downy derriere, as it brings home the fact that over the course of our evolution, butt hair has never acted as a barrier to mating success.

Another possible explanation for our posterior mustache states that hair may help to amplify our anal scent. Granted, this probably isn’t something most modern humans would aspire to, but it’s likely that early hominins used scent as an important means of communication. As such, the capacity to broadcast one’s odor over long distances would have conveyed a number of advantages, allowing our ancient ancestors to mark their territory and attract mates.


Hair helps with this as it traps oily secretions that carry scent, while also providing an environment for bacteria that consume these oils and generate yet more smells.

A third and final theory, meanwhile, posits that butt hair serves to reduce friction and chafing as we move around. By trapping the aforementioned stinky oils, hairs ensure that our cracks remain nicely lubricated, thereby protecting us from irritation and rashes.

While none of these notions have been studied in detail, it seems likely that bum hair exists for a number of different reasons, so there’s no need to despair at your unsightly crack.

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  • evolution,

  • humans,

  • weird and wonderful