So if you follow them sciency blogs and videos you will know that there’s been a big push among those who study ancient homonids to ascribe human hairlessness to persistence hunting. Barefoot running enthusiasts take this evidence and run with it in their promotion of daily long distance barefoot running. I tend to think that it’s more evidence of lack of imagination than a real theory about why we are hairless. Right now we have a few theories, for instance, the aquatic ape, hairlessness to protect against lice, and persistence hunting. We also used have to a theory that clothing could have caused hairlessness but thanks to lice studies and human genetics we know humans were naked until a few hundred thousand or so years ago but being hairless goes way further back, 1.2 or so million years ago. The reason we can figure out pretty exactly when it happened is thanks to some incredible advances in human genetics.  If you shave a chimp you will notice that he is pale under his fur.   When humans lost their fur, they also had to develop dark pigmentation to protect against UV damage from the sun.  Scientists have been able to study all the genes for skin color but of interest is MC1R.  By studying genetic drift and working backwards, scientists have been able to put the time when we lost our fur as 1.2 million years ago.   So the theory that clothing has anything to do with it us becoming hairless is out.  This has left the persistence hunter theory as front and center.  I think however, that there are just too many other things that could have happened too many other possibilities things that we haven’t really studied yet for  persistence hunting to become the default explanation.  For one persistence hunting is terribly risky.   You use up tremendous amount of calories running that much so if you have a success rate of less than 50% you are losing calories.   What is more, if you hunt in a larger group, the success rate has to be almost 100%.   There’s also the problem of running that far and then having your prey taken away by other predators.   So I’m not a huge fan of persistence running as the only or even primary reason for us becoming hairless.  I think there should be many more theories about why we lost our fur.   Not just these handful but many more possibilities.  For instance, how about fire?  We also know that fire was invented between 1 million and 2 million years ago but at the time we first captured fire we probably didn’t know how to create it just how to keep it burning if we found it from a thunderstrike.  I’m not suggesting that the fire caught early hominids fur on fire so that’s where the selective pressure is.  I presume that if a spark caught a bit of your fur on fire as an early hominid you would know enough about how to put it out.  I think it might have been more like, well suppose there was a hominid that lacked some of the hair of his fellow tribe.  He would want to keep the fire burning all the time well because it’s cold at night even in Africa.   He would keep it burning, bank it at night, bring it up again in the moring.  So maybe the rest of the tribe would not care too much,  but since there’s already a fire going then they would cook their food with it.  There have been recent studies which show that the caloric values of cooked vs raw foods is incorrect.  Raw foods give you about half the amount of calories as cooked foods, so cooking foods would give the tribe with a fire keeper a significant evolutionary advantage.   I’m not saying this is the right theory, but I just think that the persistence hunting theory has really gained too much ground recently and there need to be more theories, more ideas.   The reason more theories help us is that a new theory will give scientists who study hominids new ideas to test and perhaps show a path back to why humans became hairless 1.2 million years ago.

Advertisements