Re: An alternative to ST and AAT

Phillip Bigelow (
Fri, 08 Nov 1996 18:47:58 -0800

> Thomas Clarke wrote:

> > There are lots of saltative bipeds in Australia.

Are they saltative in EXACTLY the same way?

> > There were lots of bipedal (tripedal?) dinosaurs.

Were they bipedal in EXACTLY the same way?

> > But only one who walks like a man.

This is not true. Brachiating arboreal primates "walk like a
man" when they find themselves (infrequently) on the ground.
The only difference is that, morphologically, they don't
locomote EXACTLY in a human style gait. But that is to be
expected. After all, Tom, they ARE different species.

> > Does this not suggest the possibility of special evolutionary
> > circumstances? If the circumstances were not special then why
> > are there not lots of animals that walk like a man?

Why are there not lots of birds that walk (and run) JUST like an
ostrich? Why are there not lots of birds that walk JUST like
a stork? Why are there not lots of birds that walk JUST like
a grouse?

The answer (at the risk of sounding like I am teaching a pre-
schooler) is that every species has it's own unique character
traits. These character traits (such as style of gait, and
length of gait) can be (and usually are) acquired through
adaptive radiation from a common ancestor.
Remember Tom, that uniqueness DEFINES a species. If we used
your "logic", then all species alive would have had
to have had "special circumstances" that molded their adaptation.
This can be demonstrated to clearly NOT be the case all the time:

Example: Rheas and ostriches both shared a common adaptive
circumstance that led to their loss of flight (geographic
isolation; abundant ground food; loss of major predation).
Yet, these runner-specialized birds have a different pedal
count (three for the rhea; two for the ostrich), and a different
stride pattern and different stride length.

Similar environmental pressures for each of them; yet two different
morphological outcomes. They don't even run the same way! (see the
research done on this by Dr. James Farlow).

Tom, it amazes me that you still insist on some type of "special"
origin for hominids. It also amazes me that, in spite of us having
a similar conversation on this topic last year, you still make the
same statements today.