Friday, January 4, 2013

On hands, fists and the evolution of human violence

The famous scene above is from Stanley Kubrick's 2001: A Space Odyssey.  It depicts, in a stunning two-minute moment in film history, man's progression from using tools to kill to using them to explore as the camera tracks the rise of a bone, thrown into the air, to be replaced with a spaceship.  I am sure anthropologists could point out all the errors in this scene but this is art, not documentary, so Homo kubrickus, as I'll call our fictional ancestor, dramatically represents our rise from primitive violence.  Please watch the clip and, as you do, notice the way our hairy star is using his hand.  It turns out that H. kubrickus may be one of the most portentously ironic characters ever to drag his knuckles out of Hollywood.

From the abstract of "Protective buttressing of the human fist and the evolution of hominin hands" by Michael H. Morgan and David R. Carrier, published in the January 2013 issue of the Journal of Experimental Biology:
The derived proportions of the human hand may provide supportive buttressing that protects the hand from injury when striking with a fist. . . .  We found that peak forces, force impulses and peak jerk [rate of change in acceleration] did not differ between the closed fist and open palm strikes.  However, the structure of the human fist provides buttressing that increases the stiffness of the second MCP joint by fourfold and, as a result of force transfer . . . more than doubles the ability . . . to transmit "punching" force.  Thus, the proportions of the human hand provide a performance advantage when striking with a fist.  We propose that the derived proportions of hominin hands reflect, in part, sexual selection to improve fighting performance.
If you remember the movie, the clan from which our hairy star emerges has been run off from a watering hole in a previous scene, a clash in which all participants, from both clans, hoot and growl and feint and raise their arms in the air while shaking their hands -- the way we think of chimpanzees scaring opposing groups to take flight.  In the climactic scene above, the losing clan has returned to reclaim the watering hole.  This time they start as before -- hooting, growling, feinting, arm-waving -- until the star with the vicious smile uses the bone to beat a foe to, we presume, death.  But if Morgan and Carrier are correct, H. kubrickus jumped a step in evolution.  Instead of using the bone to club his opponent, he should have pummeled him with his fists.

"Because you have higher pressure when hitting with a fist, you are more likely to cause injury to tissue, bones, teeth, eyes and the jaw," Carrier told Jennifer Viegas of Discovery News, for her article on their research.  "Although some primatologists may argue that chimpanzees are the most aggressive apes, I think the evidence suggests that humans are substantially more violent."  Carrier cites the evolutionary fact that male humans are larger than females (which Viegas links to "men being ten times more likely to commit homicide than females in the U.S." -- a connection which may or may not be a correlation and, in either case, is not a subject of Morgan and Carrier's study), and suggests that fists are as important to females as they are to males: "Women need to fight off attackers and defend themselves from rape."

The question is whether the evolution of the human fist is coincident with the evolution of our most violent nature.  Put another way, which came first: our violent nature or our fists?  Was there a cause-and-effect relationship between human fists and violence, just as Viegas implies there is between male size and male violence?  Maybe; maybe not.  But one thing does appear probable in this specific case: art might have been more accurate than science.

It seems that the way our hairy friend in Stanley Kubrick's movie uses his hands -- the way they would have been used with tools to dig, cook, carve and build; that is, to benefit the species in a productive, nonviolent way -- is more predictive of our violent nature than if he would have balled his hands into fists and beat the crap out of his equally hairy foe at the water hole.  Why?  Think of that space ship at the end of the clip.  It's maneuvered with gripping hands on joy sticks (or similar steering devices) and gently squeezing fingertips on buttons, knobs and switches.  This is the same use of a hand as that which was used by murderers who pulled the triggers on their guns since the gun was invented, the crew of the Enola Gay when it dropped the first nuclear bomb on Hiroshima, the remote crews of today's drone aircraft firing missiles at suspected terrorists in the Middle East, and the millions of children and adults worldwide who kill virtual enemies in video games.  H. kubrickus was, indeed, ahead of his time.

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