Chimpanzee 'super strength' and what it might mean in human muscle evolution

June 26, 2017 by Janet Lathrop, University of Massachusetts Amherst
Credit: CC0 Public Domain

Since at least the 1920s, anecdotes and some studies have suggested that chimpanzees are "super strong" compared to humans, implying that their muscle fibers, the cells that make up muscles, are superior to humans.

But now a research team reports that contrary to this belief, chimp muscles' maximum dynamic force and power output is just about 1.35 times higher than human of similar size, a difference they call "modest" compared with historical, popular accounts of chimp "super strength," being many times stronger than humans.

Further, says biomechanist Brian Umberger, an expert in musculoskeletal biomechanics in kinesiology at the University of Massachusetts Amherst, the researchers found that this modest performance advantage for chimps was not due to stronger muscle fibers, but rather the different mix of muscle fibers found in chimpanzees compared to humans.

As the authors explain, the long-standing but untested assumption of chimpanzees' exceptional strength, if true, "would indicate a significant and previously unappreciated evolutionary shift in the force and/or power-producing capabilities of " in either chimps or humans, whose lines diverged some 7 or 8 million years ago.

Umberger was part of the team led by Matthew O'Neill at the University of Arizona College of Medicine, Phoenix, and others at Stony Brook University, Harvard and Ohio State University. Details of this work, supported in part by a National Science Foundation grant to Umberger, appear in the current early online edition of Proceedings of the National Academy of Sciences.

The researchers began by critically examining the scientific literature, where studies reported a wide range of estimates for how chimpanzees outstrip humans in strength and power, averaged about 1.5 times over all. But Umberger says reaching this value from such disparate reports "required a lot of analysis on our part, accounting for differences between subjects, procedures and so on." He and colleagues say 1.5 times is considerably less than anecdotal reports of chimps being several-fold stronger, but it is still a meaningful difference and explaining it could advance understanding of early human musculoskeletal evolution.

Umberger adds, "There are nearly 100 years of accounts suggesting that chimpanzees must have intrinsically superior muscle fiber properties compared with humans, yet there had been no direct tests of that idea. Such a difference would be surprising, given what we know about how similar muscle fiber properties are across species of similar body size, such as humans and chimps."

He explains that muscle fiber comes in two general types, fast-twitch, fast and powerful but fatigue quickly, and slow-twitch, which are slower and less powerful but with good endurance. "We found that within fiber types, chimp and muscle fibers were actually very similar. However, we also found that chimps have about twice as many fast-twitch fibers as humans," he notes.

For this work, the team used an approach combining isolated muscle fiber preparations, experiments and computer simulations. They directly measured the maximum isometric force and maximum shortening velocity of skeletal muscle fibers of the common chimpanzee. In general, they found that chimp limb and trunk skeletal muscle fibers are similar to humans and other mammals and "generally consistent with expectations based on body size and scaling."

Umberger, whose primary scientific contribution was in interpreting how muscle properties will affect whole-animal performance, developed computer simulation models that allowed the researchers to integrate the various data on individual muscle properties and assess their combined effects on performance.

O'Neill, Umberger and colleagues also measured the distribution of muscle fiber types and found it to be quite different in humans and chimps, who also have longer muscle fibers than humans. They combined individual measurements in the computer simulation model of muscle function to better understand what the combined effects of the experimental observations were on whole-muscle performance. When all factors were integrated, muscle produces about 1.35 times more dynamics force and power than .

Umberger says the advantage for chimps in dynamic strength and power comes from the global characteristics of whole muscles, rather than the intrinsic properties of the cells those muscles are made of. "The flip side is that humans, with a high percentage of slow-twitch fibers, are adapted for endurance, such as long-distance travel, at the expense of dynamic strength and power. When we compared chimps and humans to muscle fiber type data for other species we found that humans are the outlier, suggesting that selection for long distance, over-ground travel may have been important early in the evolution of our musculoskeletal system."

The authors conclude, "Contrary to some long-standing hypotheses, evolution has not altered the basic force, velocity or power-producing capabilities of to induce the marked differences between chimpanzees and humans in walking, running, climbing and throwing capabilities. This is a significant, but previously untested assumption. Instead, natural selection appears to have altered more global characteristics of muscle tissue, such as muscle fiber type distributions and lengths."

Explore further: Muscle fibers alone can't explain sex differences in bird song

More information: Matthew C. O'Neill el al., "Chimpanzee super strength and human skeletal muscle evolution," PNAS (2017). www.pnas.org/cgi/doi/10.1073/pnas.1619071114

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rderkis
not rated yet Jun 26, 2017
This kind of conflicts with what I read a few years ago. I am 70 and get things mixed up but the study/research I read said that there is a mechanism in the brain that governs our use of muscles. That governor like most things in nature "If you lose one thing you gain another and vice versa.
According to the study I read, that governor can ether give you the ability to use all the muscle fibers in a muscle at once or give a species much better control of those muscles at the cost of apparent strength.
We call that ability to control the muscles coordination. Humans chose to go with coordination for survival while the apes chose strength. That is why apes seem to walk so uncoordinated and have you ever seen a ape throw somthing? :-)
Now don't confuse spatial awareness with coordination because a ape has much better spatial awareness than us. Just watch them swing from branch to branch.
The article said gray matter was where the governing took place. We know more about the brain now.
rderkis
not rated yet Jun 26, 2017
After thinking about it they did not specifically use the word coordination, the words they used were "fine motor skills".
jonesdave
not rated yet Jun 26, 2017
Fair points, rderkis. However, as I assume you know, nobody "chose" anything. It was evolution that led the ancestors of both chimps and humans to develop different traits in different environments, after they split.
And yes, I have seen chimps throw stuff. Mainly their faeces! I wouldn't have them opening the bowling for a cricket team, but they can chuck stuff! And are extremely strong. I wouldn't mess with the buggers.
rderkis
not rated yet Jun 26, 2017
And are extremely strong. I wouldn't mess with the buggers.

But this article; makes it clear they are only ~.35% stronger than a man. Yet we see them rip trees out of the ground. Since their muscles are essentially the same as ours there is somthing else going on.
I don't know if it has been proven or verified but supposedly there have been examples of superhuman strength under extreme pressure is some people. (Lifting car off loved one etc)
If true that would bolster the edea that there is somthing else in play besides the makeup of the individual muscles.
rrwillsj
1 / 5 (1) Jun 27, 2017
As the writer Mackey Chandler so cleverly put it; Humans adapted to the ecology and the environment of the veldt by evolving endurance to become the 'sweaty' "Remorseless Predator".
Gigel
not rated yet Jun 27, 2017
And are extremely strong. I wouldn't mess with the buggers.

But this article; makes it clear they are only ~.35% stronger than a man. Yet we see them rip trees out of the ground. Since their muscles are essentially the same as ours there is somthing else going on.

The article says that for similar sizes chimp muscles are 1.35 times stronger than those of humans. But above that chimps are far more muscular than humans (they "walk" by their hands in trees). Maybe they also have larger arms, giving them more leverage. And as you pointed out there may be a neural basis for their strength if they sacrificed coordination for force; that would make sense if motor centers in chimps' and humans' brains are of comparable size, because then it all reduces to using the same brain capacity for 2 competing performances.
Dingbone
Jun 27, 2017
This comment has been removed by a moderator.
antialias_physorg
5 / 5 (1) Jun 27, 2017
If you evolve for swinging in trees then I don't find it surprising that 'arm strength' is something that is selected for.

Getting up a tree to escape a predator is a powerful selector. Something humans haven't had to do in quite some time.

As they note
The flip side is that humans, with a high percentage of slow-twitch fibers, are adapted for endurance, such as long-distance travel, at the expense of dynamic strength and power.

Hunting and gathering (both of which require long range travel) selects for endurance. And with the use of tools we more than make up for the lack of strength.
rderkis
not rated yet Jun 27, 2017
Here is the article I was referring to in the first comment on this article.
https://www.lives...ans.html
dnatwork
not rated yet Jun 27, 2017
This kind of conflicts with what I read a few years ago....
According to the study I read, that governor can ether give you the ability to use all the muscle fibers in a muscle at once or give a species much better control of those muscles at the cost of apparent strength.


I remembered the same article when reading this. I think both things could be going on at the same time, but these researchers seem to want their explanation to be the only one (all too common arrogance and reduction in academia).

If you combine 35% more intrinsic power per muscle cell with firing two to six times as many cells at once, you quickly get twice as much power or more. So if a human could lift 50 pounds all day, a same-size chimp could probably lift 500 pounds for a few seconds and be done.

That should be expected. Chimps have to dominate other chimps physically but briefly, humans compete more in other areas.
rderkis
not rated yet Jun 27, 2017
Hmmmmmm I call bullshit on this - mostly.

IF you spend your time climbing trees and ...
When I used to use steel tongs and ...
That and riding a racing bike ...
I could have grabbed this guy ...


I don't think that is bullshit! I think you probably actually did this stuff or at least think you did. :-)

P.S. We know what you were trying to say. :-)

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