Re: AAT Theory

chris brochu (
30 Sep 1995 12:35:20 GMT

I'm out of here after this one, and I mean it this time - this is getting
too silly, and I really have more important things to do.

"AAS" vs. "non-AAS" is a rather simplistic summary of the issue. It
sounds like you're saying, "I cannot visualize how other models work,
therefore they cannot work."

We in the archosaur business faced the same problem when the dinosaurian
nature of birds was resurrected in the 1970's - some had a hard time
seeing how one could go from a bipedal runner to a flyer, and thus stated
that the abundant evidence that it had happened nonetheless was
misinterpreted. That birds are dinosaurs is accepted now by the vast
majority of vertebrate systematists, but there are those who maintain
alternative views, largely because they have channelized themselves into
a particular idea and refuse to accept alternative explanations.

"Non-AAS" could be summarized, from my non-anthropological perspective,
thus: the immediate ancestors of hominids were arboreal animals that
were facultative bipeds on the ground. Chimps and gorillas are like this
today, though admittedly they are not our direct ancestors. As the
continuous forest cover in eastern Africa began to break up, they found a
need to move from one grove to the other. As they were already capable
of bipedal locomotion, they may have found this to be a good way of
moving on the ground, especially if carrying things like infants or food.

As stated earlier, the phylogenetic history of primates, as we understand
it, suggests nothing more elaborate than that. Neither, quite frankly,
does the anatomy of Homo sapiens. Anything beyond that would be
speculation - hence, AAS rather than AAH.

(I would welcome corrections from *serious* anthropologists - like I've
said, I don't normally do mammals.)

I find this no less explanatory, in your definition, than the AAS. That
you see it as "explaining nothing" suggests to me that _any_ reasonable
alternative would be declared such.

Finally, I *urge* some of you to read Brooks and McLennan's _Phylogeny,
Ecology, and Behavior* for an explanation as to how we reconstruct
evolutionary history.

Peace and long life,