Re: Bidedalism (bipedalism)

Pat Dooley (
27 May 1995 21:55:10 -0400

Greg Erwin writes:

>I'm not sure of the units being used in the energy cost, but it should be
>noted that the environmental change to savannah from forested area
>favoured those who could range farther for food. Animals which could
>travel for long distances in search of food sources such as scavenging
>others' kills or roots, berries and seeds did better. This ability to
>travel also developed into the ability to "run down" wounded or
>deliberately injured animals. Now we can run marathons.

There are two problems with this approach.

1) Humans are vey inefficient water conservers. They sweat too copiously
and drink too little when the opportunity arises. We can't run marathons
in hot conditions without providing an adequate number of drinking

2) The primary mechanism used by savannah animals to avoid predators is
speed. Early bipedal hominids, like modern humans, would be no match for
average lion, cheetah or hyena. Later hominids did move to the savannah
but they has brains and weapons to help them survive there.

>It is possible that the driving force behind the increase in brain size
>was temperature regulation. As the brain is very sensitive to
>overheating, redundant areas were a safety feature that were pre-adpated
>to being used in other ways. An upright body exposes much less surface
>the sun than a quadrupedal body. During this same time, hominids
>developed the large number of sweat glands, loss of body hair, and loss
>the venous network respnsible for cooling the brain in many animals,
>including australopithecines.

We don't know whether sweating evolved before or after hair loss. The big
with its hefty cooling requirements evolved long after bipedalism.

>As evolution is blind and does not have any purpose, it is important that
>we understand the immediate causes and forces selecting for various
>traits. Evolution cannot select for future utility.

Good points.

Pat Dooley

-- Greg Erwin, vice president, Humanist Association of Canada.
I saw a person wearing a T-shirt that said "Question Authority", so I said
to him, "Who are *you* to tell *me* what to do?"