Re: Hominid speciation
J. Moore (j#d#.moore@canrem.com)
Thu, 10 Aug 95 17:34:00 -0500
Pn> >present species names becoming sub-species names and so on. I
Pn> >think this would be useful in letting us point out the diffs we
Pn> >see but not lose sight of the relatedness we tend to take for
Pn> >granted and therefore forget. But I don't think it's gonna happen.
Pn> I'm not saying it should happen. Ian Tattersall made an excellent point
Pn> a few years back concerning the Neandertal/Middle Pleistocene hominid
Pn> picture. We have "archaic Homo sapiens" "Homo sapiens
Pn> neandertalensis" etc., everything being grouped into a single species.
Pn> It is interesting that this all happened in the sixties. Perhaps are
Pn> reluctance to name species of Homo has less to do with the data and more
Pn> to do with egalatarianism and anti-racism.
Could well be, at least in part. Although my argument was that,
as long as we use the names that categorize the differences that
we see, this isn't bad. We have to be able, as easily as
possible, to recognise the differences, but I think also that the
opposite, obscuring the possibility of relatedness, is of equal
importance.
Pn> Look to the points at which the fossil record begins to get muddled.
Pn> Yes, the whole thing is somewhat muddled but when we get to about 2
Pn> million years ago and then again around 500,000 years ago we get a lot
Pn> of variation. Could it be that these periods represent homiod
Pn> speciation events: punctuations, so to speak?
That was my point in the initial posting; perhaps it was unclear.
I think we are always likely, at major speciation points, to see a
lot of variation. Much of this will be within an interbreeding
population, and some will be offshoots that never really made it
into the later periods, and some holdovers will also remain, as we
see with very late holdover robust australopithecines up till
around 1.3-1.1 mya.
Pn> >There's even been, at least a few years back, a concerted attempt
Pn> >by some to push all robust australopithecines into a different
Pn> >genus entirely by bringing back the genus *Paranthropus*. I think
Pn> >that's a *real* bad idea.
Pn> I'm not sure it's so bad. After all you have a lot of distance between
Pn> Australopithecus boisei and Parathropus robustus.
Distance? In terms of time, or physique?
Pn> >The obvious justification, which has validity, is that there are
Pn> >differences in these, and other, hominids and that we would very
Pn> >likely see a species difference between, at the very least, habilis
Pn> >and sapiens if both lived today. And in using these names to make
Pn> >explicit the differences we see, and to sort out and diminish the
Pn> >confusion of all those specimens, we're doing a good thing. When
Pn> >the names themselves start confusing us, by obscuring relatedness
Pn> >and by making the phylogenies we've created seem too certain,
Pn> >we're doing a bad thing.
Pn> But by lumping everything together we may be missing indications in the
Pn> fossil record of something important. After all, there is no real
Pn> correlation between speciation and morphological variation.
That's why I think we always need the names to indicate the
differences. The difference between my position is that I think
both the differences *and the similarities* need to be easily
identified, whereas the standard naming setup in use seems to have
moved toward making only the differences easy to identify, with
the attendant suggestion that therefore presumably only the
differences are truly important. It makes the whole issue seem
more settled than it is (more then it *can* be, actually), and I
think that is unfortunate.
Pn> >This also gets into what exactly is a speciation event, which is
Pn> >problematic, not least because the term "event" helps confuse the
Pn> >issue, sounding a little too much like Tooby and DeVore's
Pn> >insisting `that hominid evolution be regarded as a discrete series
Pn> >of branches and stages' (Tooby and DeVore 1987:203) and that we
Pn> >should simply `characterize each hominid species at a given point
Pn> >in time' (Tooby and DeVore 1987:200). Phil's suggestion is more
Pn> >like Tanner's idea of "process and sequence", that is, dealing, as
Pn> >evolutionary theory should, with the whole of a population in the
Pn> >midst of an ongoing changing world.
Pn> No. That suggests that a species is an arbitrary catagory.
Pn> Phil Nicholls pnich@globalone.net
How so? It's a construct, that's for sure, but I wouldn't suggest
it's abitrary. I don't see how thinking about a species as a
population should make that species category seem arbitrary.
Nor do I see how thinking about that species living in an
evolving, changing world with other evolving, changing species
rather than in a static period as "discrete" and therefore
unconnected stages would make a species category seem arbitrary
either. Perhaps I simply didn't explain the idea fully enough.
Jim Moore (j#d#.moore@canrem.com)
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