Hairless And Sweaty

At some point in the past, humans and great apes had a common ancestor.  The homo sapiens branch of the tree then veered off in one direction and evolved into the humans of today — largely hairless, especially in comparison with other primates, except on the head and in the nether regions — whereas the great apes remained heavily furred.
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What caused the humans to take the smooth-skinned route?  The BBC has an interesting article that attempts to answer that question.  It’s not an easy question, because having a mat of fur seems to have lots of evolutionary advantages.  It protects the skin, is warmer, provides some protection against bites, and may even have a camouflage effect.  So why did the most successful primate in the history of the planet, the one that reached the top of the food chain, ditch the fur at some point in the distant past in favor of the bald look?

The theory is that the evolutionary forces began to work when our early ancestors moved out of the shadowy forests and into the savannah.  By getting out of the shade, the proto-humans moved to a setting that offered more hunting targets, more meat, and thus more protein, which would help them to develop bigger brains.  But, the savannah also featured more heat.  The heavily hirsute creatures who tried the veldt quickly became overheated and had to retreat to the cool forest, where they were left to snack on grub, worms, insects and fruit.  Our less furry ancestors were better able to adapt to the heat, and those who had more sweat glands and could sweat away the body heat were even more capable of running after and killing protein-packed prey in the hot African sunshine.  The standard forces of evolution — time, survival, and procreation — then combined to shift human bodies increasingly away from shaggy fur and toward sweaty hairlessness.  The end product was the modern human, which is both hairless and also the sweatiest primate alive.

Sweaty and hairless.  It’s almost as if evolution was trying to design a creature that could survive August in the Midwest!  Now if evolution would only answer another crucial question:  why do men who reach the AARP membership age seem to lose all of the hair on their legs?

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