This reconstruction of a Homo heidelbergensis (600,000-300,000 years ago) reminds us that we H. sapiens are not the only genus of our kind to have walked the earth, and our Homo ancestors, like us, shared an interesting quality: we lack hair.
Of course, we have some hair — our heads and genitals, and many of us have even more hair on our chests, backs, arms, and legs. But this is definitely not fur, and it matters — other primates, like chimpanzees and baboons, are covered with the stuff, and two factors can likely explain why this is so.
First, climate change around 2.8 million years ago made many areas in Africa turn from jungle to savannah. There would have been a scarcity of plant food and permanent sources of freshwater compared to earlier times, and thus, our ancestors became more reliant on meat sources, which they had to chase down. The long distances the genus Homo would have traversed across the savannahs would have caused our ancestors’ bodies to heat. And to deal with that, they likely developed a plethora of sweat glands called eccrine glands. Unlike other types of sweat glands (that predominate in other fur-covered mammals), eccrine glands don’t cluster near hair follicles, instead emitting vast quantities of sweat through skin pores — thus, being relatively hairless would have helped these primates to cool down, and take advantage of the food supply in the savannahs.
There is another benefit to hairlessness — and that is sociability. It’s hard to know whether other genus Homo had the same type of vision that we Homo sapiens have. But, in contrast with many animals, we have three types of cones in our eyes, enabling us to see a greater range of hues in a particular color spectrum. Thus, we can detect very small changes in the blood underneath the skin of other’s faces, which can help us read each other better. Babies with blue skin might be cold and need warming, sexual attraction might be shown with a blush, and a face red with anger might conjure an appropriate threat response.
Of course, we have some hair — our heads and genitals, and many of us have even more hair on our chests, backs, arms, and legs. But this is definitely not fur, and it matters — other primates, like chimpanzees and baboons, are covered with the stuff, and two factors can likely explain why this is so.
First, climate change around 2.8 million years ago made many areas in Africa turn from jungle to savannah. There would have been a scarcity of plant food and permanent sources of freshwater compared to earlier times, and thus, our ancestors became more reliant on meat sources, which they had to chase down. The long distances the genus Homo would have traversed across the savannahs would have caused our ancestors’ bodies to heat. And to deal with that, they likely developed a plethora of sweat glands called eccrine glands. Unlike other types of sweat glands (that predominate in other fur-covered mammals), eccrine glands don’t cluster near hair follicles, instead emitting vast quantities of sweat through skin pores — thus, being relatively hairless would have helped these primates to cool down, and take advantage of the food supply in the savannahs.
There is another benefit to hairlessness — and that is sociability. It’s hard to know whether other genus Homo had the same type of vision that we Homo sapiens have. But, in contrast with many animals, we have three types of cones in our eyes, enabling us to see a greater range of hues in a particular color spectrum. Thus, we can detect very small changes in the blood underneath the skin of other’s faces, which can help us read each other better. Babies with blue skin might be cold and need warming, sexual attraction might be shown with a blush, and a face red with anger might conjure an appropriate threat response.
Fyi: the “aquatic ape hypothesis” isn’t taken seriously by anthropologists — it argues that our ancestors lived in a watery environment and that’s why they lost their hair. It doesn’t stand up to the fossil record, however. (Wikipedia has a good article on it)
Sources: Scientific American “The naked truth: why humans have no fur,” Niña G Jablonski, Feb 1, 2010. Smithsonian Magazine, “Why did humans lose their fur?”, Jason Daley, Dex 11, 2018.
