Re: AAT Theory

Thomas Clarke (
2 Oct 1995 13:16:57 GMT

In article <44ndmb$> (Clara N.
Fitzgerald) writes:
> (David L Burkhead ) writes:

Actually, this is not my response, probably David's in response
to a query by me.

> >In article <44e7jk$> writes:

> > Okay. Here's my scenario. ... IOW, it's a "just-so" story.

> > Start with a mostly arboreal ape, an animal that hangs from
> >branches and feeds on fruits, nuts, leaves, whatever.
> > Situation changes slightly. The arboreal ape has to spend more
> >time on the ground. For reason, perhaps the forests are thinning and
> >.... On the ground it does
> >some walking on all fours and some walking bipedally (like modern
> >apes). Both modes are clumsy, since it's adapted to neither.

At this point you have a modern chimpanzee which has survived to the
current day, what more changed to force the proto-hominid to go
beyond the chimpanzee mode of existence?

You suggest:

> > Extensive tool use, then, as one of this animal's major survival
> >adaptations, could be favored at the expense of other traits.

As Clare notes, the progression seems to be
common ancestor -> bipedalism (Lucy) -> tools (erectus)
so the evidence seems to be that bipedalism precedes substantial
tools use. Brain size does not increase greatly until after
Lucy as well.

If Lucy had been a knuckle walker so that bipedalism only
arose later along with tool use, I could give more credence to
your story.

> > once bipedalism is established, other traits (such
> >as Wheeler's results wrt heat rejection) can come into play. These
> >traits allow access to niches that were not available before and the
> >new niches would tend to push for greater improvement in the traits.

With this I am entirely in agreement. I just think that the
seashore is probably the ideal environment for bipedalism to
become established - walk uprght or drown!

Tom Clarke