I’ve often heard (no cite) that pound-for-pound, chimpanzees are seven times as strong as humans – even though their muscles are not significantly thicker. I’ve also read that this is due to a difference in “neuromuscular efficiency”. However, in a current CS thread – “How superstrength would REALLY work” – http://boards.straightdope.com/sdmb/showthread.php?t=275033 – Blake insisted that it is due to a difference in leverage – i.e. (although he didn’t spell this out), chimps have longer arms. Is this true?
I have no expertise on anatomy, so I’ll let people better qualified explain what makes the chimp’s muscles work better than a humans.
But lest you doubt a chimp’s strength, just imagine how strong YOU’D have to be to support your own body weight while hanging from a branch, or to swing yourself from tree limbs, as chimps and orangutans can.
If chimps only had longer arms it would give them less strength, not more. I believe the difference is in the geometry of joints. Making the attachment point for tendons a little further from the pivot point allows the same muscle to exert more force at the business end.
I don’t have a good cite either, but I’ve heard that only part of it is due to leverage. The other part of it is due to the muscles themselves. The leverage part has more to do with where the tendons attach rather than the length of their limbs, as Padeye said. You would be significantly stronger if your muscles attached an inch or so further down your arm too.
There’s a genetic disease in humans that can turn you into a “superhuman” of sorts. It affects the way the muscles grow and you end up significantly stronger than the average person. I believe there are also some negative health effects assocatiated with the disease but I’m not sure what they are.
First off I never said it was due solely to a difference in leverage. Chimps are stronger than humans in large part because they have larger muscles in the upper body and muscle strength relates directly to cross sectional area. Chimp biceps are about twice the weight of humans of the same size, and the biceps are also about twice as thick. IOW that’s like comparing a fairly skinny guy with 11” biceps to Arnold Schwarzenegger’s 22” arms. Chimps are strong in no small part coz chimps have some damn big muscles.
“(PCSA) reflects the number of sarcomeres in parallel and is therefore proportional to the amount of force a muscle can produce. Muscles with high PCSAs have the capacity to exert large forces (Zajac, 1992)… all forelimb muscle masses, fascicle lengths, and PCSAs are smaller in humans than in chimpanzees”
THORPE et al 1999, AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY
The point about leverage was that pound for pound chimps still remain apparently stronger, although in reality that is largely only true for the upper body.
As for whether chimps have longer arms, the answer to that is undoubtedly yes.
“Since humans have long legs and short arms, and chimpanzees short legs and long arms, it is more realistic to assess the differences in muscle mass by taking into account segment length. Table 7 shows that when muscle masses are scaled on the basis of segment length, chimpanzees possess comparatively larger muscles than do humans for all groups except for the quadriceps, which are approximately the same.”
Thorpe again.
But it’s not the length of the arms I was referring to, it was the ratio of upper and lower arm. Even that was simplification so that we didn’t totally hijack a CS thread. Chimps also have differences in the way the bones of the lower arm interact, as well as the shoulder blade and collarbone. Their lower limbs are also designed so that they can exert force over far wider area than human legs can. But that is all still just a matter of leverage, the bones themselves don’t act as anything but levers on which the muscles can work.
Strength-wise muscle is pretty much the same for all animals from tapeworms to turkeys. Strength is proportional to cross sectional area and to a much lesser extent attachment. Chimp muscle is identical to human muscle. Similarly nerves are also pretty much the same for all vertebrates, the last big evolutionary lead being myelinisation. Chimp nerves are identical to human nerves. Chimp neuromuscular physiology is identical to human.
Chimps are stronger because they have more muscle and because of the leverage afforded by bone structure, not because they have ‘better’ muscles and nerves. That’s like saying that spiders are a thousand times stronger than humans pound for pound, so a man bitten by a radioactive spider would become super strong. It doesn’t work that way because there differences in muscle strength between spider, humans or chimps is tiny.
And that’s why I was referring not to longer arms but rather the ratio of upper and lower arm bones. The upper and lower arms in humans in about the same whereas in the chips the forearm is much longer. That allows the biceps to be attached further from the elbow joint which, as you say, increases strength.
So in short we’re comparing human legs to chimpanzee arms? Designed for different things but comparable in strength, given that distinction?
From what I understand, humans have lost certain genetic traits. If we were apes, we’d be stuck at teenagerhood physically. It is, I suppose, a trade off to pay for the brain’s energy requirements, and that in humans long-distance running was more important than titanic upper-body strength.
Cecil covered a portion of this in the first book when asked about chimpanzees wrestling humans in carnivals. You could look up the article and see if that helps you any.
http://www.straightdope.com/classics/a1_001b.html
Not many specifics, but still an interesting read.
People with long, thin arms and legs can also be strong, so there must be more involved than just how thick the muscle is in the middle. Chimpanzees probably have the best of both worlds, through millions of years of evolution and adaptation in the forests.
I suppose the OP could have asked the question in the opposite way, namely, why are we so weak by comparison? I think the answer to that is, as soon as we learned how to use tools and grew our brains a bit, the resources our bodies had formerly put into muscle now went into brain development. As we began to rely more on a long bone or heavy stick to inflict punishing blows on our enemies, our musles…atrophied as it were.
I don’t think anyone is comparing that, I certainly haven’t seen it if they have. I for one was directly comparing chimpanzee upper body strength with human upper body strength. Specifically I noted that chimp biceps are to normal human biceps what Schwarzenegger biceps are to Bill Gate’s biceps.
Since this is GQ I’m going to ask for a reference. Can you actually name one person who has the same strength as someone else despite having significantly thinner muscles? Muscle strength is necessarily related to area simply because muscles work as multiple linear motors. The thinner the muscle the fewer motors and the less power. There is some room for leeway because some muscle conations some superfluous connective tissue, but it’s not great.
I didn’t say that cross sectional area isn’t a factor at all, only that it isn’t the only factor. Think of how your biceps works to bend your arm at the elbow, which is its primary function. A tendon runs from the biceps to each of the two bones in your lower arm. By the principles of simple mechanics, if that tendon attaches, say, an inch closer to your wrist, then that gives you a mechanical advantage over someone who has the exact same muscle mass, but whose tendon attaches closer to the elbow.
Abraham Lincoln was tall and weedy looking, but the biographies all agree that his physical power was remarkable.
OK, so what you are basically saying is that strength is a combination of cross sectional area and leverage? No argument there. Humans have a strength disadvantage and speed advantage over chimps in part for precisely that reason. That’s the whole point here, the difference is not due to chimps having any difference in muscle or nerve physiology but simple anatomy.
And you’ve used Lincoln as a possible example. Note however that Lincoln was notably abnormal in his body proportions just as I said in the original post in CS. Even if we accept that Lincoln was stronger than normal for his size due to different muscle attachment points that reinforces my point that anybody trying to derive higher strength is this manner would appear grotesque and unable to pass for a normal human. Everyone who ever met Lincoln was stuck immediately by his abnormally long limbs, oversized hands and peculiar walk. And this was a man at most twice as strong as normal, not seven times stronger, which would require even more pronounced changes.
However it isn’t true to say that Lincoln was weedy looking. Nor is it immediately apparent that his strength was unusual relative to his muscle size. It may have been but it’s impossible to ascertain.
Lincoln may have appeared thin but only because he was preternaturally tall die to a genetic defect and his legs were disproportionate to his body size. Lincoln was 6’4” but much of that came from his disproportionately long legs and when seated he was described as being of normal hight for that time. IOW had his legs been proportioned he would probably have been only 5’6” and yet he weighed 185 pounds at his peak. Any 5’6” man weighing 185 pounds is by no means weedy. Indeed there are plaster casts of Lincoln’s hands that show that he was an exceptionally powerfully built man.
I have never actually seen a description of the young Lincoln as weedy and precious few of him as even skinny. He was often described as lean, spare, sinewy or angular but that is very different from skinny. Just as often though Lincoln is described as stout, muscular or powerful. In fact Lincoln being so powerfully built is often used as evidence that he did not suffer from Marfan’s syndrome as often believed, but that he suffered from other rarer genetic defects or possibly even hormonal imbalances brought on by childhood cancer.
I don’t have a cite for this, but I was under the impression that a large part of the difference was due to differences in the type of muscle tissue. I believe there are at least two types of muscle tissue, fast twitch and slow twitch. The former gives you dexterity, and the latter gives you strength. Chimps have lots of slow twitch muscle tissue and not much fast twitch tissue, so are stronger than humans with similar muscle mass. Humans have more fast twitch muscles, so have more dexterity. That’s one of the reasons I can type or play a musical instrument better than a chimp.
Before I could believe that more I’d have to see some evidence that fast and slow twitch muscles even have different peak tension. Fast twitch muscles contract faster and they run better anaerobically but I’ve never seen it suggested they are significantly weaker before, much less 3 times weaker.
And as for the idea that muscle type dictates why chimps can’t play the piano, that’s totally implausible. Chimps can’t play the piano because they lack the intelligence to be trained to do so. It’s not like chimps are just bad at playing the piano which could be accounted for by muscle type, they display no ability at all to even recognise what a piano is for. Humans are better at playing the piano with their feet than chimps are with their hands and that’s says everything we need to know about the impact of physiology IMO.