Re: Hominid speciation

J. Moore (j#d#.moore@canrem.com)
Sun, 6 Aug 95 17:22:00 -0500

Pn> A species is a group of ancestor-descendent populations, not just
Pn> populations in the here and now. In my opinion, a species may undergo
Pn> directional change over time in terms of morphological characteristics
Pn> but this itself is not enough to justify calling it a new species. For
Pn> example, if we are going to maintain that a single unbranched lineage
Pn> connects Homo habilis, Homo erectus and Homo sapiens, what is our
Pn> justification for using three species names? If no speciation event
Pn> has occurred then no new species has emerged.

Hmm, yes, well, etc. ;-) In other words, I'd tend to agree, or at
least to say that you're making a real good point, but this may be
a completely lost cause. Actually, my own wish list would be to
just shove all known hominids into *Homo*, with the various
present species names becoming sub-species names and so on. I
think this would be useful in letting us point out the diffs we
see but not lose sight of the relatedness we tend to take for
granted and therefore forget. But I don't think it's gonna happen.
There's even been, at least a few years back, a concerted attempt
by some to push all robust australopithecines into a different
genus entirely by bringing back the genus *Paranthropus*. I think
that's a *real* bad idea. (Tanner tried hard for calling habilis
*Australopithecus/Homo habilis*, to emphasize the transitional
nature of the beast, but that was a lost cause, in spite of the
fact that her view was borne out by at least the first
post-cranial bones found, which seemed to give habilis a pretty
australopithecine-like body. Is that still the case? [my info
there is old].)

The obvious justification, which has validity, is that there are
differences in these, and other, hominids and that we would very
likely see a species difference between, at the very least, habilis
and sapiens if both lived today. And in using these names to make
explicit the differences we see, and to sort out and diminish the
confusion of all those specimens, we're doing a good thing. When
the names themselves start confusing us, by obscuring relatedness
and by making the phylogenies we've created seem too certain,
we're doing a bad thing.

This also gets into what exactly is a speciation event, which is
problematic, not least because the term "event" helps confuse the
issue, sounding a little too much like Tooby and DeVore's
insisting `that hominid evolution be regarded as a discrete series
of branches and stages' (Tooby and DeVore 1987:203) and that we
should simply `characterize each hominid species at a given point
in time' (Tooby and DeVore 1987:200). Phil's suggestion is more
like Tanner's idea of "process and sequence", that is, dealing, as
evolutionary theory should, with the whole of a population in the
midst of an ongoing changing world.

Tanner's conceptualization of `Process and Sequence' is that life, and
evolution, is a process, and that the sequence of innovation is vital to
understanding that process, since later innovation are built upon
earlier ones.

Even amongst living species we have difficulty at times with saying
this is a species, and this one over here is a separate species,
etc. The idea that we can definitively do this with a collection
of bones can be charitably described as problematic, but that's
what our present naming system suggests. With living species
their behavior, if studied assiduously, can help verify or falsify
these notions, but with ancient bones we can only hope for a lot
more bones to perform the same verification/falsification. This
makes it more essential, when dealing with the past, to keep an
open mind about relatedness... much more critical than when
dealing with living species.

Refs:
Tooby, John, and Irven DeVore
1987 The Reconstruction of Hominid Behavioral Evolution Through
Strategic Modeling. The Evolution of Human Behavior: Primate Models.
Warren G. Kinzey, ed. pp. 183-237. Albany: State University of New
York Press.

Pn> Phil Nicholls pnich@globalone.net
Pn> "There is a grandeur in this view of life, with its several powers,
Pn> having been originally breathed by the Creator into a few forms or into
Pn> one; and that, whilst this planet has gone cycling on according to the
Pn> fixed law of gravity, from so simple a beginning endless forms most
Pn> beautiful and most wonderful have been and are being evolved."
Pn> [Last sentence from _On the Origin of Species_, by Charles Darwin

Here's one of my favorite Darwin quotes:
"False facts are highly injurious to the progress of science, for
they often endure long; but false views, if supported by some
evidence, do little harm, for everyone takes a salutory pleasure
in proving their falseness: and when this is done, one path toward
error is closed and the road to truth is often at the same time
opened."
Charles Darwin, 1871 *The Descent of Man and Selection
in Relation to Sex*, Chapter 21, page 909.

Jim Moore (j#d#.moore@canrem.com)

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