Re: An alternative to ST and AAT

Holly Reeser (
Sat, 02 Nov 1996 08:08:06 -0500

Phillip Bigelow wrote:
> 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?
> >They are so
> > specialised that they would find it hard to adapt to any
> > other form of life even if they could find a niche that
> > was not already occupied.
> Obviously at least SOME of these taxa SUCCEEDED at finding
> a different niche! 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. If it happened
> with their ancestors, why not in the hominid clade as well?
> >So the LCA was probably a
> > quadrupedal terrestrial species much like a chimpanzee or
> > gorilla.
> You lost me on this one. WHY?
> <pb>

Have a look at RIchard Foleys book Another Unique shows
that there was an ongoing trend towards cattarhine terrestriality by 15
mya...coinciding with a shift to drier, warmer temperatures. At this
time the gerealized arboreal niche that most primates occupied fractured
into four fairly specialized ones; two were semiterrestrial including
the line that gave rise to our CA and us. Terrestrial locomation was
already ongoing when A. ramidus came around and this creature lived in a
forested environ. It is truly doubtful that open spaces created the need
for a bipedal and terrestrial form of locomotion....I would suggest that
they just provided a way to reinforce an adaptation and thereby alwwoing
it to progress.