Re: Hominid speciation, w
J. Moore (j#d#.moore@canrem.com)
Sat, 5 Aug 95 19:37:00 -0500
Rl> I sure don't disagree here. Complete reproductive isolation simply
Rl> cannot be proven from the fossil record, and I think your point about
Rl> being too rigid regarding such possibilities of interbreeding is
Rl> injurious is probably true.
I think this is mostly an unfortunate happenstance due in large
part to much of the working out of what these creatures were and
redoing their names having occurred during the 60s and 70s, at
which time it was thought (still is, mostly) that hybridization as
a source of variation was a phenomena seen in plants but not in
animals. I don't think the idea was really given its due at that time.
That makes doing it now more difficult, and especially so since we
don't have massive numbers of hominids (too bad they weren't
aquatic shoredwellers or something ;-) and because the specimens
we have that are particularly suggestive, esp. 1805 and 1813
(which you mentioned) are anything *but* unequivocal.
Rl> KNM-ER 1805 is one such difficult specimen. It has a parasagittal
Rl> crest on one side (not really midsagittal) which some believe to be an
Rl> injury, and it does have a large nuchal crest. The mandible associared
Rl> with it appears disproportionally small, particularly with regard to the
Rl> height of the horizontal ramus, and the teeth are small. The thing that
Rl> drove me nuts was when I was trying to use discriminant analysis on the
Rl> endocasts (1978 Royal Society Conference) 1805 was continually
Rl> classified as a gorilla! Sort of embarrassing for paleoneurology....
So much for the inevitable supremacy of numbers, eh? ;-) I proposed
a magazine article once about 1805, calling it a "Skeleton in Our
Closet". The mag later used that title for something else (not
that it isn't a natural joke for the subject matter) but there are
definitely things in the habilis pile that people aren't quite
sure what to do with; too often they don't talk about them.
Rl> Others thought it was the male counterpart to KNM-ER 1813, but the shape
Rl> of the endocast is quite different between the two, so the sexual
Rl> dimorphic position doesn't appear too convincing to me.
Rl> Ralph Holloway
That seems kinda forced to me, too. Folks sometimes forget, as I
think I mentioned before, that the specimens we have are *part* of
a population, not the whole population. Much as we might like to
do so, it's unlikely we can fit each and every one into their
proper relation to the others. Each specimen with a variable
feature could be an oddball one-of-a-kind freak, a member of a
fairly large similar population, or simply a (perhaps rare)
variation, except in those few cases when we can definitively
state that a variation is due to injury or disease.
Jim Moore (j#d#.moore@canrem.com)
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