Re: ANCESTRY QUESTION?
Boris Borcic (borbor@divsun.unige.ch)
Tue, 24 Jan 1995 14:16:57 GMT
In article <3g0h5p$fnd@hammer.msfc.nasa.gov>, whorton@berea.msfc.nasa.gov
(Mark S. Whorton) wrote:
> In article <MAVERICK.95Jan22201827@cork.cs.berkeley.edu>,
maverick@cs.berkeley.edu (Vance Maverick) writes:
> |> Because it's an irregular and *extremely sparse* sample of all the
> |> animals that have ever lived. [...]
> |>
> Yes Vance, but doesn't it seem odd that there are no clear transitional
> species in the fossil record?
Archeopterix. Speaking of birds, you don't need to go the fossil record
to view cases of complete and continuous transition between two species.
There are multiple cases of extended populations of birds, around the
globe or around mountains, that constitute two species on some part of
the area they occupy. If you choose one form in this subarea, there is
a path round the globe (or mountain) along which this species transforms
continuously into the other. A complete set of locally interbreeding
intermediate forms exist *today*.
This is an inescapable direct proof of transformism.
That it hasn't effectively been used to eradicate creationist
nonsense against evolution is perhaps a consequence that
such populations don't fit directly in the simple-minded ultra-
-mechanical "gene pool & frequency" axiomatisation of evolution
lecturers barricading themselves against creationist intrusion.
It's a pity, 'cause I have a hunch that these cases could
be integrated as natural illustrations in a model a bit less
concerned with showing evolution as stupidly mechanical
(and thus less attached to a description in terms of current
state/evolution equation for a species).
Somehow, the above case of "roundabout" species looks similar,
(except for the fact that gene-flow is probably bidirectional),
to what a cut through the evolutionary tree passing by two
sibling species and by the heart of the branches to their common
ancestor (e.g. with all the intermediates), should look like.
A modelisation of evolution that used as primitive concepts
such cuts through the tree (linking distinct species by
intermediate forms) instead of oversimplified uniform gene-pools,
could presumably have the above-mentioned species as central
(instead of marginal) evidence. Which is important 'cause they
can't be denied as the partial fossil record can.
> I know that this is a standard complaint against darwinian evolution and
> some will tell their sophmore students to respond, but as a scientist, the
> simplest theory that agrees with the observed evidence is usually the
> correct one.
You are right, sophomore-level population genetics is probably
too simplistic.
Regards,
Boris Borcic
==
L'homme descend du cygne
|