Having body hair can be a real pain; that’s why getting professional body sugaring is becoming so popular! We want to have smooth skin, and hairlessness has been seen as attractive for millenia, so why do we have body hair to begin with? There’s a few theories to explain the phenomenon; none are certain, but all of them are interesting.
Body hair is seen on almost all mammals; even whales often have hair at birth! Terrestrial animals tend to have a lot of hair, and when they have enough we call it fur. It’s incredibly likely that humans’ ancestors had fur, but lost it along the way; now we just have body hair, but not enough to be called furry (for the most part). The question, then, is what happened to our furriness?
One theory suggests that one of our ancestors did a lot of aquatic living. The theory says that this chain in our evolutionary link spent time in shallow waters foraging for food. Fur is no good at aquatic insulation; it becomes soggy, thick and uncomfortable, as anyone who’s seen a dog shake their coat out can tell you. We’ve seen the link between mammals without fur and water plenty of times; aquatic mammals don’t have fur, and mammals that spend a lot of time in the water, like rhinoceri and elephants, tend to have fat as an insulator instead of a mass of hair. There’s not a lot of fossil evidence for this link, though, so scientists are unsure.
The second theory is that our ancestor moved from cooler jungle climes to hot savannahs. Savannahs would have been a good hunting ground for our ancestors, who used keen eyesight and cardiovascular endurance to wear prey down by hunting them for hours at a time; such hunting expeditions would prove exhausting in the sun with a fur coat, so we shed it. The only thing this theory doesn’t account for is the savannah becoming much cooler at night, where fur would be a good insulator. Lions, hyenas and other savanna predators all have fur, so it’s unclear that an animal needs to shed it’s hairs to adapt to warmer climes.
A final reason we might have less hair than our chimpanzee cousins is to get rid of parasites. Humans are incredibly social animals, so disease carrying insects could easily infest the tight-knit groups of our ancestors. The hairier a person is, the easier it is for insects to hide on their body, so less fur would mean less chance of disease infecting the tribe. Our ancestors likely didn’t need fur when they started losing it; we’d probably already learned how to use fire and build shelters for warmth, so we no longer needed insulation from the elements.
No matter what reason we had fur for in the past, we certainly don't seem to need it now. We don clothes to keep warm, and we have shelter and heat readily available at almost anytime. We might eventually lose our body hair altogether, but in the meantime, it’s easy to keep the hair off by getting a sugaring done regularly!