Thursday, December 20, 2012

The Power Of The Fist: An Evolutionary Saga.

So,  A new journal article argues that the human hand developed into the shape it has because the kind of hand we have makes the best possible fist for unarmed fighting.

 How was that presumed evolutionary adaptation acquired?

Well, it seems that our prehistoric male ancestors fought over sex with each other.  Women and access to them was the reward, and the guy with hands most adapted to boxing got all the women, passed his seed on widely, and, presto!, here we are with our human hands.

Those prehistoric ancestors fought with the Marquess of Queensbury Rules, I guess.

Here's more about the theory:

If you learn martial arts, one of the first things you get taught is how to make a fist properly. Classic mistakes include sticking the thumb inside the other fingers or curling it around the side. The right way is to wrap the thumb over the index and middle fingers. In this shape, the fingertips are cushioned against the pads of the palm, and the first two fingers are cushioned against the thumb pad and the thumb itself.
By getting martial artists to hit a punchbag, and measuring the forces acting on their fists, David Carrier and Michael Morgan from the University of Utah confirmed that this shape allows the various parts of the hand to buttress each other, turning a flat hand into a stiff, compact club. This channels the force of a punch into the palm, wrist, and forearm, and protects the delicate fingers.
But more controversially, Carrier and Morgan also suggest that this might explain why the proportions of our hands evolved in the first place—for stability during combat, rather than dexterity during tool use.
Compared with the hands of other apes, our palms and fingers are shorter, and our thumbs are longer, stronger, and more mobile. That makes for a stronger fist, and would have allowed “competing males to strike with greater force and power while greatly reducing the risk of injury to the hand,” they write.
It’s an idea that has divided opinion. I contacted four scientists about the study. Two expressed their respect for Carrier’s wider work but were unconvinced by his new idea (although neither wanted to comment on the record). A third—Brigitte Demes, who studies the limbs of primates at Stony Brook State University—said that the actual experiments were sound, but “the interpretation is far-fetched”.
And then there's that usual story of how all this meant a new hand shape for humans!
So, the story goes like this: Our male ancestors fought each other for mating rights. Their hand proportions evolved from those of a typical ape, to those that allowed them to whack each other without breaking their hands. With their non-self-destructing punches, our fore-fore-fore-forefathers got more sex, and gradually their hands attained the proportions of a modern human’s.
Don't you love it?  Video recorders were at the site to give us proof of the boxing matches and so on.

What are the other problems with this quite fun theory?

First,  as Ed Young states in the piece I link to, making the martial arts fist is not a natural thing for humans, and the shape we were taught,* the two-knuckle punch fist, is not the shape boxers use to make the fist.  The two-knuckle fist is efficient, sure, because the power of the punch hits a small area and the way the wrist is extended protects both it and the hand.  But one needs to have the cultural teaching to make it.  If it was the natural way to make a fist, then at least all men would make it naturally, right?

Second, as Ed Young also records, apes fight with their teeth and use open slaps instead of punches.  We don't know the shape of those prehistoric ancestors' teeth and so on, but they were probably bigger than ours.  In other words, they may have had more efficient ways of fighting than boxing, and probably did.

Third, the theory seems weak to me in the following sense:  We use our hands for most everything.  To imply that their shape is determined by one specific use, and not a terribly frequent one, most likely,  requires very strong evidence to tell us how the new shape didn't interfere with any of the more frequent tasks we have for our hands.

I'm pretty strongly in the camp of those who believe that the shape of our hands is what it is because it's good for manipulating tools (sewing leather with a needle, say) and for interacting with the environment in general.

The story in this study tells us more about the difficulty of drawing evolutionary explanations.  First, the initial data begins with a very specific group:  martial artists, and a very specific fist:  the two-knuckle-fist.  It then moves on to more general theorizing about fighting, not boxing,  and only unarmed fighting,  while holding the initial specific example at its core.  That makes it easy to ignore the obvious alternative fighting methods.  Finally, it argues that dexterity in object manipulation could be achieved with hands of different shape, but fails to notice that this is quite as likely to apply for fighting applications.
*To this day, when I make a fist the two front knuckles stick out and the rest recede.  The power of repeated practice!  The callouses do disappear over time, however.  For more on martial arts by me, see this blog post on how to make a fist and this one on the womanly art of self-defense.