Re: AAT - energetics

Alex Duncan (
7 Jul 1995 21:46:50 GMT

In article <> Elaine Morgan, writes:

>Alex Duncan argues very reasonably that in the open spaces bwtween the
>trees those hominids "that were most adept at moving from tree to tree
>on the ground would have been selected for". Sure. And the most adept
>primates at covering the ground rapidly are (and would then have been)
>the quadrupedal ones. Four legs are faster than two. Stamina doesn't
>come into it. Until you have learned to walk the first hundred
>yards you cannot know that in a few million years you're going to
>be good at the marathon. After five million years and extensive
>remodelling of skelt[eton and muscles we are quite good at moving on
>two legs- but we are talking about the ancestral ape. We have been twenty
>times reminded that for an ape walking on two legs takes no more energy
>that walking on four (no less either) Okay, but running on two takes a
>hell of a lot more energy for an ape - something like four times - and
>it is SLOWER.

First off, I'm not suggesting "preadaptation" with its connotations that
somehow the ancestral critter "knew" what its descendants would need to
survive and evolved accordingly. I'm suggesting "exaptation" -- which
implies that a feature that evolved for one purpose (or as an
epiphenomenon of another feature -- like bipedalism in gibbons) was later
coopted to serve another. The best analogy I know of is feathers, which
probably evolved to help small carnivorous dinosaurs maintain
homeothermy, and later proved to be useful for flight.
Second, what is your citation for statements about energetic
efficiency and speed for bipedal apes. I have one. Try Rodman & McHenry
in AJPA 1981 (I can be more precise if you want). Chimps use no less
energy walking quadrupedally than they do walking bipedally. They don't
slow to a crawl when moving bipedally either, as anyone who's seen a
bipedal threat display can attest.
You seem remarkably misinformed. I guess you would have to be to
support your position, because the facts certainly don't support it.
Actually, I guess I'm encouraged that many of the AAT supporters cite
you, because it sure is easy to shoot down.

Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086