When Hairy Was Good
There's a reason why our ancestors weren't as shiny as we modern humans are. And it has to do with babies - ancient offspring needed hair to hold on to while we were padding around on all fours. Jamie Lawson reports on the evolution of body hair.
I’ll tell you what’s wrong with the World today. It’s simple. Never mind your fancy socio-economic ideas, keep your politics, I’m going to give it to you straight. Here it is, are you ready?
<ahem>
*People aren’t hairy enough*
No no, I’m serious. There was a day, a few thousand years ago, when everything was simpler. There were more trees, more open spaces, plenty of impala on the plain, a nice water source just over there and all you had to worry about was whether today would be the day that a leopard would catch you, drag you up a tree and eat you alive. Men were men, women were women and everyone was hairy.Ah, those were the days when there wasn’t a problem that couldn’t be solved by giving someone a damn good grooming and the sight of a woman going about her business with an infant clinging to her fur was entirely routine. You just don’t see that anymore. Unless, I suppose, you inhabit a 150,000 year timewarp, or you're a lowland gorilla. Neither seem very likely.
Of all the primates, in fact, humans are the baldest. Even compared to our own group, the apes, we are naked. The other apes - the chimps, gorillas, orangutans and gibbons - are all very hairy indeed and show no signs of wanting to change, while we humans stand alone in our nudity; a great big shiny anomaly in an otherwise hirsute world. And 'stand' is the operative word. For as well as being more-or-less bald, humans, ever the rebels, have also developed a neat trick of standing upright on two feet, forgoing the more traditional four-legged posture of our primate cousins.
Linking these two features together is by no means new, but researcher Lia Amaral of the University of Sao Paolo, has advanced a novel explanation for the evolution of human bipedality based on the loss of our body hair. According to Amaral, it all comes down to where you put your babies.
The females of the other ape species carry their young around on their bodies. Obviously, in order for this not to end in tragedy, the infants must have something to hold on to that can carry their weight. Given that apes are, for the most part, covered in hair, it is strongly likely, reasons Amaral, that body hair should feature in infant carrying. Furthermore, Amaral proposes that where infants become too heavy to rely solely on the friction of mum’s coat, body posture should be expected to compensate.Amaral’s investigations into the physical properties of orangutan, gibbon and gorilla hair support the hypothesis. The lightest babies - baby orangs and gibbons - cling happily to the front of mum, relying on the friction and tensile strength of her hair to stop them sliding from her body and plummeting helplessly to the forest floor as she swings her merry way through the trees. Among gorillas, where the babies are too heavy for hair alone to support them, a four-legged, knuckle-walking stance has developed to provide the infant with a more stable platform on which to sprawl (i.e. the gentle slope of mum’s great, hairy back).
Which is where humans come in.
As human females became less and less hairy, human babies had less and less to hold on to and ran a greater and greater risk of sliding off and being eaten by a leopard. An upright, bipedal posture means that a human mother can hold her infant in her arms, thus solving the problem. Obviously, this leads to a secondary issue that a female with her arms full of baby cannot use her arms for other things like, for example, eating, so other, unencumbered individuals need to be drafted in to help. This, concludes Amaral, may be the point of origin for human social behaviour, thereby neatly linking both bipedality and the extreme gregariousness of humans to the loss of body hair. Ta-daa.
So there you have it. The source of our ungainly stance and our social organisation? A glorious combination of the young and the bald. Excellent. At least now we know why women are so fond of fur coats.
Why not try one of Jamie's other articles:
- Eh? - It's easier to see big cats than cars
- Mad? - Students not safe without GPS phones
Or perhaps something a bit hairier:
- Curious cures - Mint helps hairy ladies
- Animal mysteries - The sasquatch
Your Say:
Er, we lost the hair so we evolved arms or we evolved arms and so lost the hair?
Alex
I do not think that people have a problem with explanations based on evolutionary ideas... the problem is that when people go far away from the data they have with explanations that are circular. So the line separating crap and good science is very thin.
Losing hair forced humans to stand up straight to carry the offspring... but why did we lose our hair in the first place?
Isabel Arend
Image: Myka H
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