Why are Chimps So Strong?

November 11, 2011 6:41 AM

How is it chimps are stronger than humans?

Chimps are known to be much stronger than human beings. How is that? Presumably their individual muscles are more or less comparable to ours, ounce for ounce.

Is this something we gave up in the nerve department when we evolved towards fine motor control, or is it a matter of leverage, or what?

posted by musofire to pets & animals (13 answers total)

This Slate article lists several reasons. For example:

Even though chimpanzees weigh less than humans, more of their mass is concentrated in their powerful arms. But a more important factor seems to be the structure of the muscles themselves. A chimpanzee's skeletal muscle has longer fibers than the human equivalent and can generate twice the work output over a wider range of motion.

posted by mullacc at 6:47 AM on November 11, 2011 [5 favorites]

Our surplus motor neurons allow us to engage smaller portions of our muscles at any given time. We can engage just a few muscle fibers for delicate tasks like threading a needle, and progressively more for tasks that require more force. Conversely, since chimps have fewer motor neurons, each neuron triggers a higher number of muscle fibers. So using a muscle becomes more of an all-or-nothing proposition for chimps. As a result, chimps often end up using more muscle than they need.

The Secret To Chimp Strength
posted by griphus at 6:47 AM on November 11, 2011 [2 favorites]

Your premise may be flawed. On preview, see mullacc's response, though I took a different reading. Yes, chimps appear to be relatively stronger than humans, but not five to eight times more so (figures I had heard before dipping into that Slate article).
posted by Terminal Verbosity at 6:51 AM on November 11, 2011

In addition to biology, chimp's psychological differences also make them seem stronger. We don't expect a burst of violent energy from most humans, but chimps come from an environment where a decisive melee is necessary. The ability of a chimp to lash out emphasizes their strength. Even if humans are potentially very strong, our modern comforts have made us relatively soft.
posted by marcin_zissou at 7:06 AM on November 11, 2011 [2 favorites]

A couple things to think about: Muscle tissue burns calories just by existing. If you have a lot of muscle mass you'll need to eat more. Lets assume that muscles with stronger strength/weight ratios are also burn more calories then weaker muscles.

If that's the case, then from an evolutionary perspective it makes sense that you'd have weaker muscles, overall, if you don't need the strong ones in your ecological niche. So humans on the plain, mostly using tools rather then brute strength wouldn't need the same level of muscles as chimps spending a lot of time in trees.

I was going to say that humans have some muscles (like the jaw) that are stronger then others in terms of strength density, but according to wikipedia all of our muscles have about the same density of fibers, with each fiber pulling 0.3 micro-newton, apparently.
posted by delmoi at 7:07 AM on November 11, 2011

I've heard it explained as a difference ratio between fast and slow twitch muscles. The trade-off was that a human can run a marathon.
posted by RobotHero at 8:01 AM on November 11, 2011 [1 favorite]

The arms of chimps are very muscular and the way in which they're connected to the skeleton, as well as the structure of the joints, has evolved to maximise torque and mechanical advantage. Chimps don't need quite the same degree of dexterity and fine control that humans do. They trade some of that for the ability to exert larger forces.

Plus other reasons people have mentioned.
posted by le morte de bea arthur at 8:02 AM on November 11, 2011

Don't forget the role of the media in these kinds of stories. Yes, chimps are stronger. But they're also aggressive, wild animals with claws and fangs. That part seems to be cast to the wayside, with an image of Bedtime for Bonzo.

Even if chimps weren't stronger than humans, getting attacked by one would be devastating.
posted by Cool Papa Bell at 8:22 AM on November 11, 2011 [1 favorite]

Chimps also don't have much of anything in the way of subcutaneous fat, so an average human arm looks bulkier than a chimp arm because of our padding, while a chimp's arm is solid muscle and bone.
posted by The otter lady at 9:03 AM on November 11, 2011 [1 favorite]

I think that there is a lot of perception of the attack here too. They may or may not be 10 times as strong as a man but they are 10 times as ferocious when they attack. A resolute human attacker is going to be much stronger than a surprised timid defender.

Griphus has an interesting answer. Chimps are always using all of their strength. How about a comparison between a strong human in an act of all out strength and a chimp? Maybe it isn't fair because the humans are training and don't represent normal individuals?

Other similar chip numbers:
http://www.straightdope.com/columns/read/2/can-a-90-lb-chimp-clobber-a-full-grown-man

1260lb two hand pull
847lb one hand pull (would a two hand pull be 2500lb?) (straightdope indicates that this was leveraged so it is sort of like a dead lift?)
600 lb dead lift (they must be able to do better)

With world's strongest man numbers:
http://en.wikipedia.org/wiki/World's_Strongest_Man
1100lb dead lift (sort of like a leveraged two hand pull?)

Or power lifting:
http://en.wikipedia.org/wiki/Powerlifting
700-900lb dead lift

If only we could get chimps to weight train.
posted by bdc34 at 9:41 AM on November 11, 2011

Only if you ignore our access to .50 machine guns.

All kidding aside, these stats are bunk. In every possible situation a chimp is stronger? This is crap journalists write. The average chimp cannot bench anywhere near what the average human can. They do have stronger arm strength. Only journalists make dumb comparisons like "a chimp is stronger than a human.". Like everything else, it depends.
posted by Ironmouth at 12:01 PM on November 11, 2011

Yeah, I think the strength thing is way overblown. Pretty much any wild animal bigger than a mouse is dangerous. Hell, a *squirrel* will fuck you up if you get in its way. They've got claws, teeth and a lack of the sort of existential dread that holds humans back. Multiply that nastiness by a factor of 50 and it's obvious why they have the reputation they do.
posted by pjaust at 1:21 PM on November 11, 2011

Nitpick: Chimps do not have claws. As members of the Order Primates, they have nails.

Unfortunately, I cannot find the image online they showed me in several of my primatology classes of de-fleshed great apes side by side. The chimp's upper body consists of more muscles than a human body does. As a species, we are more gracile in our skeletal and body structure than chimps, who are basically short and stocky.

For what it's worth, I was taught in class that the secret behind chimp strength is the same that griphus mentioned: humans fine fine our muscles in order to do detailed work.
posted by avagoyle at 6:26 AM on November 12, 2011