Why are humans so much weaker than primates of comparable size?

Why are humans pound for pound so much weaker than Gorillas, Orangutans and Chimpanzees. I understand that an adult male chimpanzee likely weighs around 200 pounds, but also that an average adult male chimpanzee is massively stronger than even the strongest humans.

To be precise, what is it about our physiology or anatomy that accounts for this difference. And is there some evolutionary trade off that I’m not seeing. Are we better runners or throwers for example? Of course I know that our intelligence gives us a vast advantage, but I’m asking specifically about the muscular and skeletal systems.

Longer arms w/ muscle attachments farther from the joint ( better lever ), heavier muscle mass and, apparently ( or arguably - I think this might still be at the hypothesis stage ), a different neural structure that causes more of an “all or nothing” contraction of muscle fibers.

On the neural level one trade off would be much finer motor control for humans vis-a-vis the other great apes. The more effective levers of a chimpanzee arm can also pull and tear much, much better than a human arm, but it also slows the overall motion - you could probably throw better than a chimp.

More generally humans are built for endurance running. Very, very few mammals can outpace a well-conditioned human over the long haul. Those multi-day “ultramarathons” covering thousands of miles certain deranged individuals participate in for “fun”? Well, they would kill most critters quickly - certainly no other great ape is even remotely capable of such a feat. They just aren’t built for it.

On the topic of humans being built to run, watch this video of a persistence hunt: the kudu quarry eventually collapses from exhaustion after being chased for eight hours by a bushman hunter.

A point to keep in my mind that is that “much much stronger” is very subjective. Other apes have stronger up bodies, humans have stronger lower bodies, so it’s hard to find a fair comparison.

To give you an example of this, you can look at the example in Cecil’s column. A 165 pound chimp using its entire body pulls 847 pounds, while a man of the same size can only manage 210 pounds. If we are to believe that figure then a 165 pound man can’t walk even two steps while carrying someone his own size on his back, since that would entail his legs alone lifting his own upper body weight plus that of the carried weight, each step. That’s a weight well over 210 pounds. Which is the tip off that something isn’t kosher about these figures. Presumably the human isn’t using their legs.

I’ve looked long and hard for reliable studies on comparative chimp/human strength but I can’t find any. If anyone knows of any I’d love to see them. I’ve seen quite few studies doing comparisons based on muscle physiology but the results there are usually ambiguous, suggesting that for overall body humans and chimps are about on par.

There’s no doubt that chimps are stronger than humans for the reasons that Tamerlane suggests, but how much stronger is something I’ve never seen reliably quantified.

I don’t see that there’s a problem.
The study said “pull,” not “lift.” Lifting a person and walking with them is much different from pulling a load - why would you think they are the same?

I don’t know about those figures in Ceicil’s column. From the Wiki on Powerlifting and deadlifting:

This would seem to indicate that a well conditioned human can manage similar feats of strength as a your run of the mill chimp. I think there might be more at play here than you think , beowulff

“Well conditioned?”
Try “The strongest Human in the world” vs. some average Chimp, who doesn’t even know he’s being tested.

If you read Cecil’s article, it appears that the “one-hand pull” is something like a lat row, where the feet are braced against a wall, and a handle is pulled, using the arms and back muscles. Based on this, it doesn’t seem like there is much to dispute about the strength of primates.

Well…that’s, as you say, a well-conditioned human. The average chimp doesn’t spend several hours a day doing nothing but lifting weights. Yes, it gets more “excercise” than the average human, what with all the climbing, swinging, etc… but it’s nowhere near the level of championship lifters, who spend untold hours not only working out, but eating very high-protein diets, and more often than not use supplements and hormones.

Another factor to be considered is the type of muscle fiber, and how “well developed” it is. There’s two proteins in muscle that work together do the actual contracting, actin and myosin. Myosin has small little “heads” that grab ahold of the actin, and pull it towards the center of the muscle fiber, causing a contraction. If there are more heads on the myosin, or just more myosin in general, you’re going to get a stronger connection, and a larger force per muscle fiber.

This is the reason those two “strongest boys in the world” are so…well…strong. (One is in Germany, the other in the US…both are between 2 and 5, I think.) They both have untold amounts of myosin in their muscle. There’s an enzyme called myostatin that, in a nutshell, eats myosin. One of the boys produces very little myostatin, and the other one isn’t affected nearly as much by the myostatin (I forget which one is which.)

I’m not arguing that the men mentioned are exceptional. However, I think that the test mentioned is full of opportunities to fail, or have it’s data influenced by other problems. Anyone who works out knows that you can “cheat” isolation exercises, and I find it hard to believe that the chimp was able to understand and perform the action to a fair scientific distinction.

It is also worth noting that Cecil didn’t tell us if the test was performed by lots of humans of all shapes and sizes. I’m the same weight as the man noted and I’m certain I could do better than 210. Mostly because I use that motion a lot in my day to day work, and I’ve pulled cable a deal heavier than that on a number of occasions. My partner who is considerably larger (350 or so and 6’4 ) can double or triple my pulls with little effort.

I’m not arguing that humans and chimps are equal, but rather that it seems that a number of factors are at play here, and it’s not a simple clear cut case of muscles. If that was the case then a human could never even approach a chimps numbers and yet we have some motivated ones who do. We also know that in life or death situations, even non conditioned small humans are capable of enormous feats of strength like lifting logs or small cars off of loved ones.

Evolution develops traits necessary for survival. Things not needed are generally lost to conserve energy. The bountiful food we enjoy now was not always the case. Being able to survive on minimal nutrition plays a strong role in our genetic makeup.

Our communication skills and intelligence obviously gives us enough advantage to be the dominant specias on the planet, able to survive in all environments with the help of our tools. Developing massive upper body strength simply wasn’t required for us, and wasn’t genetically selected for.

Chimps on the other hand, rely extensively on living in trees for protection and food. A scenario that strongly selects for specimens with superior upper body strength for their size. Even gorillas are execellent climbers. That is simply what their genetic history has made them into. You’ll also note significant differences in the digestive systems of most primates. They have a longer gut, putting them closer to the herbivore end of the dietary scale. They are not primarily hunters, so their running ability is limited.

If the muscles of the leg are capable of extending the knee joint under a given load, then they are capable of doing so. Whether the load is applied when the joint is horizontal or vertical is irrelevant. The only difference between “lift” and pull" in this example is orientation. If a person can straighten the knees with a 120lb load on each knee while standing, why would they be incapable of doing so when they are sitting in rowing position?

If anything the lifting limit should be considerably lower because it involves more muscle groups, most of them considerably weaker then the legs.

There was a show, I believe on prime time TV, where a chimpanzee beat a human in tug of war, human falls in water, chimpanzee stands, smiling, waving arms in the air.

The YouTube link’s been posted here before. It’s another classic example of what I’m talking about. The chimp used its legs by bracing itself in a rowing position against a low wall. The human stood up and didn’t even attempt to brace. The the human lay down on his side. I would have beaten the human just as easily under those circumstances.

It’s been about 40 years and I still understand that some Brit explaining everything understands what’s important. It is how things are, ignoring the millenia.

And Blake will never be romantic. :wink:

(thought I could get away with this elsewhere) ;))

Perhaps we did not need strong muscles because we developed tactics and inventions (hand axes, spears, flake tools, etc) that decreased the need for stronger muscles and the metabolic energy that would’ve gone into muscles went elsewhere.

Our teeth are smaller than other apes supposedly because we have been cutting and cooking our food for a while. Could be the same thing.

According to debate on this board:

Issues of A&P that are involved are things like distance of tendon connections from the joint, surface area of bones (allowing more tension w/o ripping tendons off of bone) as well as a mutation in the MYH16 gene (which only applies to jaw muscles, but still).

http://en.wikipedia.org/wiki/MYH16_gene

[Gives Droppy a great big wet, sloppy kiss]Mwah. How’s that for romantic?[/GDAGBWSK]

There’s also the consideration that chimps use their arms for locomotion. Any limbs used for locomotion will be far stronger than limbs that aren’t. One famous example of a human who uses his arms for locomotion is Rene Kirby, who was featured in Shallow Hal. That dude has some seriously strong arms.

How much do you think Rene weighs? His mostly unused legs have to weigh almost nothing compared to the average in-shape person, yet his upper body is no doubt as strong as a bodybuilder. So a straight pound-for-pound comparison is unfair to the average human, whose long, muscular legs add a lot of weight to the total.