Re: An alternative to ST and AAT

Paul Crowley (
Mon, 28 Oct 96 19:50:51 GMT

In article <> "Phillip Bigelow" writes:

> Paul Crowley wrote:
> > I was mainly objecting to the meaning that bipedalism was
> > an adaptation of an arboreal species to a terrestrial niche.
> > Purely arboreal species that exist today are remarkably
> > restricted in location, niche and habitat.
> Why discuss "purely" arboreal species in the context?

Because it's normal; see your own words:

> How do you think chimpanzees and gorillas
> came to be? At some point, one of their arboreal ancestor taxa
> moved from a purely arboreal niche to one less so.

This is probably true, but a lot depends on how far back it
happened. I take the view that it could have been 20mya to 40mya;
that there have long been largely terrestrial niches for primates;
that it is the largely terrestrial species that are more widely
dispersed and are the most successful and most adaptable; that,
owning to taphonic bias, terrestrial species are the least well
represented in the fossil record and this has inevitably
distorted PA thinking.

The primate species that adapted to the ground probably did it
in the absence of competition. It would not have happened often.

> If it happened
> with their ancestors, why not in the hominid clade as well?

The niche would almost certainly have been already filled.