Re: AAT Theory

Phil Nicholls (
Fri, 03 Nov 1995 19:16:34 GMT

Troy Kelley <> graced us with the following words:

>> (H. M. Hubey) wrote:
>>>OF course, human biped motion is not too efficient.
>>That depends on the speed:
>>"At maximum running speed human bipedalism is twice as expensive
>>energetically as estimated for a quadrupedal mammal of the same body
>>"However,at average walking speed (4.5 km h^-1) human bipedalism is
>>slightly more efficient than is quadrupedalism in the average mammal.."
>>From:Aiello and Dean._An Introduction to Human Evolutionary Anatomy_
>> Academic Press 1990,p.272.

>It seems to me that running speed would be the most improtant variable if
>you were evolving in a savanna type environment.

Only if running were an important component of your adaptation.

> The fact that humans have such a slow running speed coupled with the
>fact that it is very expensive in terms of energy coupled with the fact
>that the savanna is typically a very hot environment makes one wonder why
>bipedalism would have evolved at all. I am sorry, but I don't accept the
>traditional, pat answer of cooling the body through reduced exposure to
>the sun. There are plenty ways to get cool besides "going bipedial", and
>no other animals show this tendanancy.

There are often multiple solutions to any problem. In evolution the
solution taken often has as much to do with previous evolutionary
history as anything else. Not all solutions were available to early
hominids. The important thing is that biomechanically bipedalism is a
form of terrestrial locomotion and it is therefore reasonable to look
for explanations that explain bipedalism as a terrestrial phenomenia.

>Again, I would like to see other people post ideas as to why bipedalism
>evolved instead of the AATers continually having to defend their
>positions. I posted this request once before and I was simply told to go
>read the literature, which was essentually a brush off. If you have a
>good theory to bipealism, please post it.


In other words, you want folks to do your homework for you. You have
taken the position that explanations proposed by anthropologists are
unsatisfactory yet it turns out that you don't know what those
explanations are and have not really investigated them.
Phil Nicholls
"To ask a question you must first know most of the answer"
-Robert Sheckley