Being a human is a pretty sweet deal on the whole. Then again, we do have our own unique problems to deal with: bills, existential crises, and acne. But why do humans have it so bad when it comes to acne, while most other animals appear to get off scot-free? Like many things, you can blame your evolutionary past.
Acne, scientifically known as Acne vulgaris, occurs when hair follicles become clogged up with skin oils and dead skin cells. Those characteristic red bumps emerge because the dermal layer of skin has become irritated and inflamed, often as a response to Propionibacterium acnes, a bacteria that usually live peacefully on our outer skin and deep in our pores.
Despite what many assume, cleanliness has relatively little to do with acne, but it can be affected by factors like diet and genetics. It’s also one of the most common diseases in the world, although some groups of people (such as the Kitavan Islanders of Papua New Guinea) don’t seem to get acne at all. It usually arises in early puberty, namely because hormone changes cause the sebaceous glands in the skin to kick out more of an oily secretion known as sebum. Most mammals produce sebum as a way of lubricating and waterproofing their skin by creating a waxy coating. It can also help to protect your body against illness by acting as a sealed barrier to germs that might penetrate the skin.
Here’s where the problem lies. Humans have evolved to be considerably less hairy than our other evolutionary forebears. Nevertheless, our sebaceous glands continue to pump out a fair dollop of sebum on our skin. Without a thick covering of fur on our bodies to "soak it up", according to evolutionary theorists Stephen Kellet and Paul Gilbert, the sebum builds up, leaving our pores more prone to getting clogged and breaking out.
It's a similar problem faced by short-haired dogs and cats. Certain breeds are susceptible to pimples during their awkward-teen phase, most likely as a result of sebum buildup. Persian cats are especially susceptible to feline acne around their face and chins, where the fur is considerably shorter than the rest of the body. However, it's not nearly as prevalent as it is with us hairless humans.
Acne, they suggest, could therefore be a result of our relatively recent change from hair-covered hominid to naked, upright apes. However, this vestigial throwback continues to live in our DNA fairly quietly because it doesn’t reduce our ability to survive, reproduce, and pass on our genes.
So, next time your skin breaks out with some zits, blame the luscious locks of evolutionary cousins from millions of years ago and your overachieving sebaceous glands