Re: Hominid speciation
Phil Nicholls (pnich@globalone.net)
Wed, 09 Aug 1995 03:28:53 GMT
j#d#.moore@canrem.com (J. Moore) wrote:
>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.
I'm not saying it should happen. Ian Tattersall made an excellent
point a few years back concerning the Neandertal/Middle Pleistocene
hominid picture. We have "archaic Homo sapiens" "Homo sapiens
neandertalensis" etc., everything being grouped into a single species.
It is interesting that this all happened in the sixties. Perhaps are
reluctance to name species of Homo has less to do with the data and
more to do with egalatarianism and anti-racism.
Look to the points at which the fossil record begins to get muddled.
Yes, the whole thing is somewhat muddled but when we get to about 2
million years ago and then again around 500,000 years ago we get a lot
of variation. Could it be that these periods represent homiod
speciation events: punctuations, so to speak?
>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].)
I'm not sure it's so bad. After all you have a lot of distance
between Australopithecus boisei and Parathropus robustus.
>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.
But by lumping everything together we may be missing indications in
the fossil record of something important. After all, there is no real
correlation between speciation and morphological variation.
>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.
No. That suggests that a species is an arbitrary catagory.
Phil Nicholls pnich@globalone.net
"There is a grandeur in this view of life, with its several powers, having
been originally breathed by the Creator into a few forms or into one; and
that, whilst this planet has gone cycling on according to the fixed law of
gravity, from so simple a beginning endless forms most beautiful and most
wonderful have been and are being evolved."
[Last sentence from _On the Origin of Species_, by Charles Darwin
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