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Why Are Chimpanzees Stronger Than Humans?

Chimps are far stronger than we are - but why?

Contributor

January 14, 2013

This summer, two chimpanzees attacked a graduate student at the Jane Goodall Institute Chimpanzee Eden. It wasn’t pretty:

In fact, the unfortunate student probably would have been better off had he been attacked by two humans. Chimps are far stronger than we are. Slate writes:

A chimpanzee had, pound for pound, as much as twice the strength of a human when it came to pulling weights. The apes beat us in leg strength, too, despite our reliance on our legs for locomotion. A 2006 study found that bonobos can jump one-third higher than top-level human athletes, and bonobo legs generate as much force as humans nearly two times heavier.

Other, more impressive figures often pop up when chimp attacks happen. Some say that chimps are five to eight times stronger than humans, but those figures come from an old, poorly designed study, says John Hawkes, an evolutionary biologist:

The suspicious claim seems to have originated in a flapper-era study conducted by a biologist named John Bauman. … But the “five times” figure was refuted 20 years after Bauman’s experiments. In 1943, Glen Finch of the Yale primate laboratory rigged an apparatus to test the arm strength of eight captive chimpanzees. An adult male chimp, he found, pulled about the same weight as an adult man. Once he’d corrected the measurement for their smaller body sizes, chimpanzees did turn out to be stronger than humans—but not by a factor of five or anything close to it.

So apes are definitely stronger than humans, probably around twice as strong. But why? Scientific American tries to explain:

They say chimps are three to five times stronger than humans—something Hawkes would argue isn’t proven—but their explanation for why might still pass muster. They say that a big reason chimps can lift heavier things than we can, is that they have less control over how much muscle they use each time they lift. Humans have a lot more fine motor control than chimps: we can do things like play a guitar, paint teeny tiny lines or thread a needle.

Chimps can’t, because of the way their neurons activate their muscles—they can’t pick and choose just a few muscle fibers at a time. We might not be able to fight off a chimp, but we can make some pretty amazing needlepoints.

Image: David Heyes