Evolutionary theorists have put forth numerous hypotheses for why humans became the naked mole rats of the primate world. Did we adapt to semi-aquatic environments? Does bare skin help us sweat to keep cool while hunting during the heat of the day? Did we lose our fur to read each other’s emotional responses such as fuming or blushing?
One popular idea that has gone in and out of favor since it was proposed is called the aquatic ape theory. The hypothesis suggests that human ancestors lived on the savannahs of Africa, gathering and hunting prey. But during the dry season, they would move to oases and lakesides and wade into shallow waters to collect aquatic tubers, shellfish or other food sources.
A more widely accepted theory is that, when human ancestors moved from the cool shady forests into the savannah, they needed better thermoregulation. Losing all that fur made it possible for hominins to hunt during the day in the hot grasslands without overheating. An increase in sweat glands, many more than other primates, also kept early humans on the cool side. The development of fire and clothing meant that humans could keep cool during the day and cozy up at night.
But these are not the only possibilities, and perhaps the loss of hair is due to a combination of factors.
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