Why did we lose all our fur? There are several hypotheses, but probably so that we could cool down more easily. However, nobody knows the actual reason why we lost our fur and there is no way of knowing when we lost it, as well.
We are the only hairless ape, but we are obviously not the only hairless animal. Reptiles and fish have scales, not fur. Birds have feathers, not fur. A lot of insects and spiders have fur, but it is different to the fur on animals. It is made of a different substance than animal hair and insects and spiders use them to sense the world around them. We are also not the only mammal without hair. Whales, dolphins, and other mammals that live in the sea don’t have fur because it wouldn’t be an advantage and soggy fur would pull them down. Elephants, rhinos, and hippos don’t have fur so that they can lose heat. And many other animals have different kinds of hair, from long to short, and from soft to bristly. However, out of all the species of ape, of which we are one, we are the only species that don’t have fur. Why is that?
Well, the easy answer is that no one knows for definite, although there are three theories, one of which is more likely than the others. Also, it is worth pointing out that we are not completely hairless. We have the hair on our heads, facial hair in men, and hair under the arms and around the genitals. We are also covered in very fine hair, which is thicker in some people than others. This type of hair is called vellus hair and it is different to the fur on other apes. It is fine and short, and it grows out of very shallow hair follicles. These are the hairs and the follicles that stand up when you get goosebumps.
Here are the three theories with the least likeliest first. The least likeliest theory is that we lost our fur so that we could wade into water to catch shellfish and aquatic tubers. The theory is that early humans lived as hunter gatherers on the savannah. In the dry season, food became hard to find, so they moved to oases, rivers, lakes, or any wet area they could find and they found their food in the shallow water. They lost their fur because fur doesn’t help insulate animals in water and makes it hard to wade, as well as taking longer to dry than skin. There is no real evidence showing that people lived near water in the dry season or that they lost their fur during this time. There are also furry mammals, such as otters, and beavers, that live in water.
The second least likeliest theory is that we lost our fur to get rid of pests. Apes are constantly plagued by insects, fleas, and other parasites that live in their fur and bite them. They spend hours grooming each other to get rid of these parasites. Being hairless would remove the risk from these disease carrying parasites. The problem with this theory is that if it were true, it would be a reason for all other apes to lose their fur as well, which they have not done. Secondly, being hairless puts us at greater risk of being bitten by mosquitoes, which also carry diseases. Apes still get bitten, but their thick fur provides them some protection.
The most likely theory is the thermoregulation theory. At some point, humans came out of forests and started hunting on the grasslands. We are the only species that can eat, drink, breathe properly, and cool ourselves down while we run. This enabled us to start hunting through persistence hunting. That means a group of humans would run after an animal until it got too hot and dropped from exhaustion. When humans lost their fur, they developed an enormous number of sweat glands, far more than any other animal. These sweat glands helped us cool down on the hot plains and having no fur kept us cool. Trying to do persistence hunting in a fur coat would have led to hyperthermia and made it impossible. There is an opposing argument that even though it kept us cool during the day, we ran the risk of hypothermia at night if we didn’t have a fur coat. However, it is possible that we discovered fire and started wearing clothes around this time. If we can wear the fur of other animals to keep warm at night, we don’t need our own.
There is one more theory, but I have no idea how likely it is. The theory is that we lost our hair so that we could read each other’s emotions more accurately. We have three cones in our eyes, which allows us to see shades of colors that most other mammals can’t see. The extra cone allows us to see the color in the face and we can know when someone is aroused, angry, sad, or sick. We couldn’t see this if we were still covered in fur. Some interesting research has shown that other primates with no hair on their faces also have three cones in their eyes, while primates with furry faces only have two cones. Perhaps there is not one single reason. Perhaps it is a combination of several of these theories. And this is what I learned today.
Photo by Pixabay: https://www.pexels.com/photo/man-holding-wood-cane-40141/
Sources
https://www.bbc.com/future/article/20230310-why-dont-humans-have-fur
https://www.smithsonianmag.com/science-nature/why-did-humans-evolve-lose-fur-180970980