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“Our work is the first detailed study of the biology and mechanics of chimpanzee muscle tissue,” O’Neill told Gizmodo. “Our results show that the main difference between chimpanzee and human muscle is in fiber distribution, with chimpanzees having a much higher fraction of fast fibers than humans, on average,” adding that “all of our measurements of chimpanzee muscle are new.”

Later, data was run through a computer program that simulated the virtual muscles of human and chimps based on fiber composition. The model revealed chimp muscle is about 1.35 times more powerful than the human variety, as reported in the journal Proceedings of the National Academy of SciencesBut because humans are much heavier than a chimp, it’s safe to say that in absolute terms a typical human is more powerful than a typical chimp. There goes this myth, too.

” Thus, the superior mass-specific muscular performance of chimpanzees does not stem from differences in isometric force-generating capabilities or maximum shortening velocities—as has long been suggested—but rather is due in part to differences in MHC isoform content and fiber length,” the authors wrote.

O’Neill says it’s likely other apes have similar muscle strength to chimpanzees. Humans seem to be the odd ones. Indeed, when the team compared the muscle fiber in various mammals like mice, cats, dogs, horses or macaques, they found that only two animals had more slow-twitch fibers: the lethargic slow loris and humans.


Humans and distant cousins Slow Lorises are built for endurance…. Credit: Wikimedia Commons.

Fast-twitch fibers give mammals a competitive advantage when it comes to doing high-intensity tasks like climbing a tree or lifting a heavy bolder. We’re not feeble, though. Because we humans have more slow-twitch fibers, we’re better suited for endurance tasks like distance running, and during mankind’s great exodus out of Africa this certainly helped. Not to mention that human hunters could simply tire their pay around while hunting. Another benefit of slow-twitch fibers is they consume less metabolic energy, freeing energy that enabled humans’ bigger brains. Without this feature, you could say humans might have never come to conquer the world.

“We propose that the hominin lineage experienced a decline in maximum dynamic force and power output during the past 7–8 million years in response to selection for repetitive, low-cost contractile behavior,” the authors concluded.

[HEY, HUMAN, NOW GO READ] Are humans apes?