Re: Bipedalism and other factors and AAT

Pat Dooley (patdooley@aol.com)
28 Jun 1995 23:19:29 -0400

I wrote:

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

pnich@globalone.net (Phillip Nicholls) wrote:

>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.

Me:

And the wading is a relatively recent innovation for them. Evolution
doesn't
work that fast.

Me:

>>What are the real advantages of wading compared to quadrupedalism?

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

Him:

>Data?

Me:

Try a little geometry, or trigonometry if common sense doesn't tell you
why.

Me:

>>2) Lower energy usage compared to swimming.

Him:

>Data?

Me:

How long can you tread water, compared to simply standing in it? How long
can you wade compared to swimming?

The energy efficiency of wading reduces as water depth increases. The
energy
cost of swimming is constant once the water is deep enough to sustain
swimming. For a bipedal ape, the point of equal efficiency is likely to
be between knee-deep and chest-deep. For a quadruped, the range within
which they can choose between swimming and wading is much more limited.

In circumstances in which wading is more efficient, whether that be
measured in terms of energy expenditure or food gathering efficiency,
primates often wade bipedally rather than swimming quadrupedally.

>>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.)

Him:

>Bonobos wade into SHALLOW streams in ankle-deep water.

Me:

It's a bit hard to tell from the reference you gave previously. However,
if the water was only ankle deep, there would have been no advantage
to the Bononbos wading bipedally to catch fish lurking amongst floating
leaves.

Pat Dooley