Re: Alex's gibbon-like CA

Alex Duncan (
8 Nov 1995 12:34:20 GMT

In article <> Paul Crowley, writes:

>We can only guess at the set of fortuitous circumstances that enabled
>a very small group of protohominids to adopt true bipedalism. They
>are most unlikely to have arisen from forces operating on the
>population as a whole. This is where your thinking (and general PA
>thought) is so bad. Does it come from the weakness of the human
>brain at conceiving large numbers? The odds are billions to hundreds
>- or ten million to one.

There is nothing about anything I've written that suggests I think that
the environment changed and an ENTIRE SPECIES made the transition to
part-time terrestrial bipedalism necessitated by the change in habitat.
I agree with you that significant evolutionary change probably happens
within small, isolated subpopulations. Frankly, I don't see how you've
read that ("entire species evolution") into what I've written, as I never
intended it to be read that way.

Conditions during the terminal Miocene were ideal for the isolation of
small subpopulations of once-widespread taxa.

As far as your comment about "general PA thought" goes, again, I can't
help but think that it arises from ignorance about what "general PA
thought" is. The majority of workers in the field think of the origin of
new hominid taxa in terms of punctuated equilibria. The sole major
exception to this are people like Wolpoff, who think that H. erectus
somehow evolved "species entire" into H. sapiens.

Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086