Chimpanzees are 2 X as strong as humans

So says John Hawks in Slate.

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Greg - do you have a source for that? Hawks makes the case that the higher claims are based on a flawed outlier study and that more recent studies support about a factor of 2.

It does strike me as underestimate. There was an incident a few years back where a chimp got loose from the Central Park Zoo and was overturning garbage cans like they were ashtrays.

In any case no one should have been surprised by Travis' rampage. Why do people allow chimps to be owned as pets? This is insane.

Why do people allow chimps to be owned as pets?

Come on: the comedy potential is incalculable. You can laugh and laugh at chimp antics for years (decades, even) before it finally snaps and goes on a rampage. Is the fun worth the risk of death or disfigurement? I think we all know the answer is yes.

MRW, Hawks doesn't exactly make the case that the higher claims were based on a flawed outlier study - he mentions two studies and asserts that one is right and the other is wrong, without giving any reasons for preferring the lower figure. (There's also a study based on jumping ability he mentions which shows that bonobo muscles generate twice as much force, but when we compare chimps to humans we're probably more interested in upper body strength).

Here's Frans de Waal quoting the 5 times figure for arm pulling strength, probably from the Bauman study, and the 2X figure for power output per pound of muscle from the jumping study:…

He also says that a chimp can do one-finger pull-ups. I really don't think that a human is only a factor of 2 away from being able to do that.

This kind of figure would need to be based on some kind of population average - the average humans versus the average chimp (therefore _not_ a high centile human football player versus an average chimp).

And there would need to be different figures for males and females - since chimps have a much greater ratio of male to female weight/ strength than humans.

If they are strong enough to tear you limb from limb, measurement of their excess strength above that doesn't much matter.

By bioIgnoramus (not verified) on 26 Feb 2009 #permalink

I don't get why he links to the original 1926 study, but then doesn't link to any of the studies he says refute it.

I can find the Finch paper, but where are the "repeated tests [from] the 1960s"? Were they published?

By Jason Malloy (not verified) on 26 Feb 2009 #permalink

This seems rather odd - why would chimpanzees be stronger than humans? Offhand, the only thing I can think of is simple leverage, and that what is at work here is mechanical advantage. But from what's being written, it seems that the muscle fibers themselves generate a greater force. That seems wrong. They're our cousins, after all, and still use the same actin/myosin setup. What am I missing?

By ScentOfViolets (not verified) on 26 Feb 2009 #permalink

OK, well, we do know one thing: 2X stronger or 5X stronger, an angry chimp can rip your face off, no sweat. (Also pull off hands and other floppy stuff, from previous chimp attacks.)

So I'd say avoid them if at all possible. Not very funny, IMO, to need a face transplant.

Check out his recent blog post - there, though not in the Slate article, he mentions they have a different mechanical advantage for at least some motions. As for the muscle itself, perhaps there are trade-offs between strength and things like endurance, speed, energy efficiency in use, energy efficiency at rest - I don't know. Certainly, muscles shouldn't get weaker per unit mass just for the sake of getting weaker.

By Eric J. Johnson (not verified) on 26 Feb 2009 #permalink

The one-arm pull strength figure I recall from Physical Anthropology in 1955 was 1150 lbs for a female chimp vs 200 lbs for a Harvard football player.

By Jim Thomerson (not verified) on 26 Feb 2009 #permalink

Thanks all.

The 1960's work was started by a guy named William Edwards, who did research for the army. He ran the first real controlled experiments, and had a detailed critique of the earlier work. None of it is online but abstracts. The Finch work in 1943 was thorough enough to convince Ernest Hooton that the 5x figure was an exaggeration; everything since then has been adding significant digits. There's a fairly deep anatomical literature on muscle in primates.

Muscle is surprisingly complicated. There are different heavy-chain myosins with partially overlapping expression in different muscles. Clark et al. (1993) found seven genes involved in "energy production from muscle protein under starvation conditions" had recurrent positive selection on the hominid lineage. So our ancestors had self-digesting muscles, I suppose. Gregory Wray's lab has been doing some work on regulation of muscle energetics; I expect they'll have a paper sometime this year. In living people and birds one of the more interesting components of variation in strength is mitochondrial volume; but I haven't yet found a good reference on this for non-human primates.

Anyway, I think ACTN3 is a good model to consider. Why the null allele? Consider all hypotheses, and see if they work in the Pleistocene, because it's very likely we're looking at multiple similar instances.

I'm not sure why people find these anecdotes like one-fingered pull-ups so persuasive. If my arms were on a 40-kg body with 8-inch fingers that lock, I could do one-fingered pull-ups too!

There's another point besides just muscular strength. Not to put too fine a point on it, Travis the Chimp mauled the lady - he took her face off with his teeth. Sorry, but there's no nice way to say that. Modern humans can't do that stuff, not even Hannibal Lecter. Take the speed of movement and the teeth, plus 2x pulling strength, plus dominance, and it adds up to a nightmare waiting to happen.

Diana's right, it's insanity. Plus it's not respecting animals for what they are - they're not us. Closest living relative still means very different.

By Sandgroper (not verified) on 26 Feb 2009 #permalink

coldequation -

I didn't say he *proved* the case, just that he made one. In that contest, Greg's simple assertion seems a little lacking. That doesn't mean he's not right, it just seems like Hawks' article requires a bit more than a one word refutation. Additionally, he did not just cite 3 studies.

While Rob Bishop may well be quite stupid, his actual quote was that the law would be ineffective "unless the monkey was willing to chase the woman from Connecticut over to New York State."

It seems he was making the point that the law falls short of prohibiting keeping primates as pets.

The following statement by the reporter was a paraphrase for which no quote was provided.

He compared the 100 attacks over 10 years to the 100,000 people who go to the hospital every year with dog bites.

Personally, I support the law as written and would also support a law banning the keeping of all dangerous wild animals as pets. Legislators may have felt that using commerce was the most effective legal means of eliminating the practice.

The point is that the law does not prohibit keeping primates as pets.