Re: Evolution doesn't "force"...

Tom Clarke (clarke@longwood.cs.ucf.edu)
10 Oct 1995 21:21:55 -0400

j#d#.moore@canrem.com (J. Moore) writes:

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

>You seem to be making a common but incorrect assumption. I would
>guess you don't realize that the question you ask here is a
>non-evolutionary one: "what forced them to change?" Change happens
>during evolution, and nothing need "force" it.

Rhetoric. Shorthand. A way of putting things in smooth English
(I hope).

You have protohominids running around Africa. They are no longer
protohominds. They changed. The standard method of change in biology
is evolution. Evolutionary changes are in response to selection
pressures, they don't just happen. In a manner of speaking these
selection pressures can be said to "force" the change. I am well
aware that there is no teleological force at work.

> It^Hf the change
>isn't excessively harmful, it can endure and even spread. You are
>also getting into some fuzzy ground when you use a phrase like
>"beyond the chimpanzee mode of existence". Chimpanzees, in an
>appropriate environment, have been a pretty successful species.
>Only recent habitat destruction has caused them major troubles.

Oops. I flew off a bit there. You were talking about genetic drift.
Somehow I doubt if a tree dweller proto-homind could just drift into
being a human (and another sub-population drift into being chimps).

About the chimps. I thought that was my point. They were well adapted.
So why change?

>By way of more explanation of this point (from a previous post of
>mine):
>It could be said to be luck that our earliest ancestors more
>often used a method of locomotion that chanced to allow later
>innovations and adaptation to far wider environments. Both
>locomotor biases, if undertaken in an appropriate environment,
>are quite effective. Yet our bias toward more bipedalism later,
>by chance, allowed the ever increasing use of many different
>environments, while the bias toward more quadrupedalism ended up
>restricting the other descendants of the ape stem population to
>smaller and unfortunately now fast dwindling areas.

So you are saying that the environment was locomotion neutral?
Then why did speciation occur? The the two groupsthat will
eventually become the two species have to be isolated long
enough to develop reproduction isolation. Different niches will
do it - but you are saying the niche is the same. That leaves
a different environment or locale. What different locale do you
propose for humans as opposed to chimps?

Tom Clarke

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