Re: Palaeontology (1)
J. Moore (j#d#.moore@canrem.com)
Sat, 12 Aug 95 17:29:00 -0500
El> On Wed, 2 Aug 1995, Elaine Morgan wrote:
El> > They seem to be saying: "The chimpanzee became quadrupedal because it
El> > needed to increase its range. The hominid became bipedal because it
El> > needed to increase its range."
El> >
El> > If they did resemble one another closely, we would need a very good
El> > reason why one lot would respond to the advent of savannah mosaic by
El> > becoming quadrupedal and the other by becoming bipedal.
Elaine should note that they said each was adapting to its
environment; note that the environments were not said to be
identical; that's something she either mistakenly read into the
piece or has deliberately mispresented (I don't know which).
However, my view on this is more like Ralph's. Just as we see
differences in tool use for specific tasks amongst different
populations of common chimpanzees, there is no reason to feel that
differences in locomotor styles could not arise in the ape stem
(last common ancestor) population, even in roughly similar
environments.
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.
Rl> days) regarding its affinities proves almost impossible. The impression
Rl> I have is far different from Elaine's. I see a lot of diversity of
Rl> pongids throughout the Miocene and probably into the Pliocene. I don't
Rl> have any trouble at all believing that two different species of ape,
Rl> living in roughly sympatric regions could show different adaptations to
Rl> roughly similar environmental changes, i.e., one becoming more
Rl> proficient at knuckle-walking, the other becoming more proficient at
Rl> bipedalism. I think Elaine expects too much homogeneity both in the
Rl> fossil record and in evolutionary responses to chaning environments via
Rl> mutation, selection, and drift. Minor differences in habitat
Rl> distribution, gene frequencies, etc, within a species can eventually
Rl> lead to some profound adaptational differences and thus morphological
Rl> components.
Rl> Ralph Holloway
Jim Moore (j#d#.moore@canrem.com)
* Q-Blue 2.0 *
|