Re: Bipedalism and other factors and AAT

Phil Nicholls (
Tue, 27 Jun 1995 21:58:54 GMT (Pat Dooley) wrote:

>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?

Lowland Gorillas wade into swamps on a regular basis. They are not as
well known as Mountain gorillas but a recent Nature special shows them
doing it rather clearly -- water up to their waste covering their

>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.

Macaques, in general, don't go into water so deep they have to stand
bipedally. Some do but the point is they show no special changes in
their muscluloskeletal systems.

>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?

Kawabe, M. and Mano T. (1972) Ecology and Behavior of the wild
proboscis monkey (Nasalis larvatus, Wurmb) in Sabah, Malaysia,
PRIMATES 13:213-228.

>>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.)

Bonobos wade into SHALLOW streams in ankle-deep water.

>Pat Dooley

Phil Nicholls "To ask a question you must first know most of the answer.
Semper Alouatta! - Robert Sheckley