Re: AAT Theory

H. M. Hubey (
13 Oct 1995 17:12:53 -0400 (J. Moore) writes:

> (Gerrit Hanenburg) writes:

>>apes.Apes are bad quadrupeds especially on the long distance.
>>However the study of Rodman and McHenry(1980) has shown that for a
>>chimpanzee walking bipedally is no more and no less energetically expensive
>>than walking quadrupedally.If selection for cursorial locomotion was
>>significant then any slight variation in the direction of more efficient

>It's strange to question empirical results but a simple
>mechanics contradicts the conclusion that they'd be
>equal. The only possibility is that the use of the arms
>offsets the use of the muscles of the back but over long
>distances it would make a difference.
> Regards, Mark

>It's not "strange" to question empirical results, but it's really
>stupid to dismiss them in favor of unsupported armchair whimsy
>(i.e. a "Hubeyism").

What is really stupid is to question things one doesn't understand.

I doubt that you are in any position to give lectures on
mechanics or biomechanics to anyone. I guarantee that you
cannot give them to me.

First you have to understand what is being discussed. What
exactly is "energy efficiency" or being "energetically expensive"?

Second you should understand if the thingamagic being measured
should be called this (whatever it is).

Third you should understand whether this variable that has been
so-named is really the variable that should be used as proxy
to answer some burning question.

Fourth, an expert not only knows what he knows, but also knows
what he doesn't know. And you ain't one because you fall on your
face when you confuse physical concepts, physics with some
words and phrases you memorized.

Now let's look into it.

>You should consider using the sorts of mathematical models that
>paleoanthropologists use to rigorously test their theories.

If it didn't come from someone who's spent the last few weeks
filling up the newsgroup with verbiage I could take this more
seriously. But let me play along. Let's see the "sorts of
mathematical models paleoanthropologists use to rigorously
test their theories" (as if you know what rigor is).

Do they use

1) small sample theory -- statistics?
2) linear algebraic models?
3) deterministic differential equation models
4) stochastic differential equation models
5) correlation-regression analysis

So which of these were being used? It's in your court.

so now, let's get back to energy efficiency. What is it? Is it
not the amount of oxygen consumption divided by something (usually
mass)? So then what is it? It's how much energy is being used
per lb of mass (assuming that the experiments have been done
correctly). Is this the only way of measuring efficiency of
locomotion? What about taking into account other factors like
total distance traveled, or the speed at which it travels? And
what is it being measured against?

So then what does the result of the empirical study mean? If the
chimp walked 100 feet and used X amount of oxygen that's all it
says. A human could probably travel 100 feet on all fours with
a heavy weight on his back and not expend appreciably more energy
than on two feet. So what?

Now reread what I wrote. The chimp is bent over already. his back
muscles have to hold up his frame in the biped position and his
muscles will tire. If he has to lift things the situation gets
worse; now his back muscles have to do more work to hold up his
frame in biped position. Common sense (and mechanics) says so.

That also explains the other common sensical observation; chimps
spend more time in quadped position and not biped because it is
more difficult (in walking).


Regards, Mark