Re: Bipedalism and other factors and AAT

Pat Dooley (
26 Jun 1995 22:22:33 -0400

Jim Moore writes:

>Some gorillas, various macaques and the proboscis monkey spend
>varying amounts of time in all those places, but show none of the
>supposed AAH adatations. They utilise common ape and monkey locomotor
>behavior (a combination of quadrapedalism, brachiation, and bipedalism)
>in each of these places. All are overwhelmingly quadrapedal on the
>ground and in the water, despite claims by some AAH proponents that they
>inevitably effect bipdal posture when in the water.

I didn't know gorillas spent much time in the water. A simple moat seems
to be enough to keep them confined at many zoos. Where did you get
that information?

I've seen plenty of information on Macaques wading into water. I've never
anything about them going in to any depth on four legs. Where did you get
that information.

Proboscis monkeys are not often observed in the wild. I've not seen
that suggests they are "overwhelming quadrupedal" in the water. Where did
you get that information?

>Various environments have been suggested by different AAH proponents;
>all state that a major reason that these water environments were
>necessary for the evolution of bipedalism is to help support the body
>weight of the animal. Note that this necessarily means that the animal
>must be well over waist deep in the water during much of the time that
>it isn't sitting or lying. Knee-deep water isn't going to help support
>body weight. Another major reason used is the claim that this
>chest-deep water environment is much safer than being out in a
>relatively open area where you have a chance to spot predators, hence
>the other post(s) on the subject of predators.

That "supporting weight" reason is a new one on me. Archimedes would
soon tell you that quadrupedal entry into the water would provide more

What are the real advantages of wading compared to quadrupedalism?

1) Better vision across the surface of the water and back to land.

2) Lower energy usage compared to swimming.

3) Less disturbance of the water while looking for prey (.c.f. earlier
post on Bonobos wading in streams and catching small fish hiding
under floating leaves.)

Pat Dooley