Monday, March 07, 2005

Chimp vs. Human

The recent attack by several captive chimpanzees on St. James and LaDonna Davis at a California sanctuary has generated a burst of Internet chatter on the relative bodily strength of these animals as compared to our own. It seems to be almost universally acknowleged that adult chimps are somewhere between four and eight times as strong as are humans despite being somewhat smaller by weight on average than a human of similar age. Mr. Davis was grievously injured in this attack - according to various reports all of his fingers were lost, one foot was severed, much of his face, including his lips, nose and one eye were torn off, etc. Simply awful.

But does it require any kind of immense and seemingly improbable disproportionality of physical strength to inflict injuries like these? Judging solely from the scanty injury reports I've read, my guess is that most of these injuries are bite damage. Most animals have disproportional powerful jaws and teeth compared to humans, and this includes the great apes. So they certainly wouldn't be at a disadvantage to us when it comes to using teeth and jaws to cause injury, and nothing in Mr. Davis' list of injuries seems to me to be beyond what a human could also cause if they were sufficiently enraged and put aside the social constraints that normally limit such behavior. Humans are fully capable of biting off fingers, toes, lips, noses, ears, etc. We don't, as a rule, but we certainly can.

Various sites I've looked at give anecdotal evidence of chimpanzee Herculean feats of strength, but they don't strike me as dispositive. One site mentions that adult chimps have no problem dragging three-hundred pound logs around on the ground - a feat of strength they suggest would be beyond human capacity without specialized training. Frankly, I find this ridiculous. I'm no athlete, but I know I can drag three-hundred pound logs around quite easily. In a pinch, I could probably shoulder a three-hundred pound log and march off with it. And I haven't spent my life climbing trees and otherwise living the chimp life, which offers considerably more opportunity to keep the old body in peak physical condition. Another site offers the results of a test in a zoo enclosure where a metering device was connected to a rope where they could actually measure chimpanzee pull strength. Two examples where presented, one in the eight-hundred pound range and one around twelve-hundred pounds of pull. This they compare to a human effort of two-hundred pounds or so. Again, this seems pretty silly. Weightlifters regularly deadlift more than eight-hundred pounds, and that's a true lift, not a jerk where the body's mass can be used to multiply an instantaneous force.

This is not to say chimps aren't strong - they are clearly very strong indeed. What I think we're seeing here is that people have anthropomorphized chimpanzees to a great extent. The truth is that they are what they are - powerful apes with a very different morphology and lifestyle than ours. Humans are larger on average than chimpanzees, but much of that size is concentrated in our legs, which are much larger proportionally than are the legs of chimps. Interestingly, no site I can find even mentions a comparison between the relative strength of chimp and human legs. The implicit assumption seems to be that upper-body strength should be roughly proportional, which seems pretty strange considering humans and chimps don't live the same way even if all modern cultural and technological adaptations are removed from the scenario. Humans are cursorial, while chimps are arboreal. We are weaker proportionally in the upper body and stronger proportionally in the lower body. How you get from there to the 'four to eight times stronger' position that seems to dominate the conventional wisdom is unclear.

2 Comments:

At 3:27 PM, Blogger Pallab said...

A very appropriate and well thought out article.

 
At 12:58 AM, Blogger Tom said...

vey good thoughts on strenth,i'm very interested in these matters are animal muscle fibers really stronger than a mans or do they have muscle attatchments to bones to give them more of a machanical advantage or both? i appreciate your thoughts

 

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