Path: utzoo!attcan!uunet!mcsun!ukc!harrier.ukc.ac.uk!sss3
From: sss3@ukc.ac.uk (S.S.Sturrock)
Newsgroups: sci.bio
Subject: Hominid evolution
Message-ID: <6781@harrier.ukc.ac.uk>
Date: 31 Jan 91 10:09:49 GMT
References: <106@tdatirv.UUCP> <6763@harrier.ukc.ac.uk> <111@tdatirv.UUCP>
Reply-To: sss3@ukc.ac.uk (S.S.Sturrock)
Organization: Computing Lab, University of Kent at Canterbury, UK.
Lines: 46

In article <111@tdatirv.UUCP> sarima@tdatirv.UUCP (Stanley Friesen) writes:
>..... the discovery of Australopithecus afarensis has changed that, now
>even cladists are tending to accept that species as either a direct ancestor,
>or a very close relative of our direct ancestor.  ...................... 
>
>Note that even the place of A. africanus in our family tree is hardly settled.
>Some still consider it a potential ancestor of Homo habilis.
>
>>Primate evolution is a rather difficult subject due to the sparse
>>fossil record, man does not die in very good places!
>
>Actually, it is by far the *most* complete fossil record of any vertebrate.
>Much of the current problems are, in my opinion, caused by the fact that
>we are actually picking up subtle geographic variations without having
>access to the intermediate populations.  I know of no other group were
>such a welter of minor variants of all sorts are known.  The main problem
>is to figure out which variants belong together in one species, since the
>variants show extensive discordance in features.  (I.e. it is impossible
>to generate a consistant cladogram that includes all of them).
>

HOLD IT, where did you get that?  The most complete fossil record of any
vertebrate?  What about the mammoth, we actually have complete specimens
of that.  How many specimens of hominid species are there?  Not many, no
wonder they can't generate a decent cladogram, not that it would mean anything
if they did!

You said yourself that A. afarensis may be a close relative of our direct
ancestor, as I did.  What about A. robustus if we are going to discuss
hominid evolution, there have been all sorts of mistakes made with that
one due to sexual dimorphism.  Look, there aren't enough specimens, no
matter what you might think.  Besides I'm inclined to think that a lot of
the problem is due to inadequate dating of specimens.

While we are at it, the reason cladistics does not work is because it relies
on similarities of morphology, what about homomorphy?  Also, how can it
be applied to fragmentary remains of hominids?  Cladistics relies on
primitive and advanced features to produce a tree, the problem today is that
all species are equally evolved, they are at the same point in time.  Some
species may have a primitive feature (according to us) but may also be
advanced in other ways.  Also, a similar external feature may evolve
more than once.  I don't object to evolutionary trees but they aren't
gospel (come to think of it neither is the Gospel :-) )  Species are just
arbitrary groups *we* made, nature couldn't care less!  Before you get too
anoyed, I am just playing devils advocate, I don't know one way or the other,
there are people out there who think they do, I remain sceptical.


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