Re: AAT Theory

H. M. Hubey (
10 Oct 1995 00:27:06 -0400 (Tom Clarke) writes:

> (Gerrit Hanenburg) writes:

>>Bipedal locomotion in humans is more efficient then quadrupedalism in
>>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.

>This is not what I have read. Are they perhaps distinguishing between
>quadrapedal locomotion and knuckle walking?

Perhaps the wrong measurement is being used to imply things
that it shouldn't imply.

My guess is that the oxygen consumption rate is being measured and
being used for everything that has to do with locomotion.

IT doesn't take into account things like the wear and tear
on the knuckles for long walks on land. It wouldn't take
into account the fact that the apes center of gravity is not
over its hips and that if it did try to lift anything and carry
it would put a tremendous amount of stress on its back. As the
apes are shaped now, they are like cantilever beams and the
type of analysis that's applied to bones such as Euler buckling
of bones is not applicable because the big stresses are not
on the bones in this manner. The animal's stance is more like
a jacknife and it would get worse if it lifted anything.
[Naturally they are not fixed at one end like cantilever beams
but the buckling load calculations or stress calculations would
have to have one end fixed and that would make it resemble
a cantilever beam.]

This is not any kind of efficiency for walking, bipedal,
half-bipedal, third-bipedal or any other kind of less
than full bipedal (i.e. like humans). Only the buoyancy of
the water provides the necessary support to be able to sustain
this position for any length of time, and there'd be no
pressure for them to become bipedal but rather the reverse
they'd be better off reverting back to quadripedalism if
they came off the trees.

>being forced to live on the ground by loss of forest and finding the
>bipedal route better than the quadrapedal route. If the environment
>forces them to run, they will be pretty poor runners and not survive
>very well.

I am in agreement with you fully. They would have gained more
by quadripedalism since the babies already had the clinging
reflex. They would have just ridden their mommas like little
cowboys and cowgirls and they would have retained their grasping
ability but remained quadripedal or stayed the way they are now.
That's probably why the chimps and other apes are the way they
are. There had to be something else for the hominid line.


Regards, Mark