Humans and apes

[B.J.Tindall]

Jason,
This would imply that a DNA sequence is not susceptible to corruption by
selection. Isn't this wishful thinking? If a gene has a product, such as an
enzyme then the selective pressures on that enzyme will potentially lead to
"corruption by selection", which in turn will potentially lead to
corruption of the gene sequence. You appear to be implying that gene
sequences are not subject to convergent or parallel evolution (among other
effects). There is certainly growing evidence for the eukaryotes acquiring
certain genes from their prokaryotic symbionts (in extreme cases these
"symbionts" are now mitochondria or chloroplasts). It is unclear to me how
the Neighbor-Joining, Maximum Parsimony or Maximum Likelihood approaches
take convergent or parallel evolution into account. Certainly gene transfer
is not part of any of these models, and is usually evident only when the
end result is "way off track" compared to other data. This of course
touches on what John wrote concerning the phenetic and cladistic approaches
to handling data.
Brian

>At 15:50 15.3.2003 -0500, Jason de Koning wrote:
>I also renew my claim that neutrally evolving characters should be
>preferred to those susceptible to corruption by selection.  If we are
>interested in extracting historical signal from traits that change
>through time, the ones that evolve on neutral trajectories have the
>lowest probability of being misleading.  Another advantage of using
>molecular characters (apart from their abundance, and their relative
>selective neutrality) is that we know a lot about their rates of
>evolution, and have realistic models to aid in phylogenetic inference.
>We also have models that can account for variable selection pressure
>along lineages.  The models are not perfect, but it is true that we
>have a much more comprehensive understanding of the strengths and
>limitations of molecular data, than we currently have for morphological.
>
>> John:
>> If that is to be the case, it would seem that there is no point in
>> doing any morphologically based systematics, no point in making
>> comparisons between neutral gene trees and morphological trees, and no
>> point in comparing molecular trees with morphological trees
>
>I don't agree.  There is a point, and the point is to weigh all
>evidence when it can be obtained, in order to do our work with
>integrity.  (Also, of course, to learn about the continuity of
>phenotypic transitions, and the rates of morphological and molecular
>evolution, which are interesting for non-systematics reasons.)
>
>Cheers,
>- Jason
>
>
>________________________________________________________________________
>__
>   A.P. Jason de Koning, Doctoral student        Email: apjdk at albany.edu
>     Department of Biological Sciences             Lab:  (518) 442-4347
>     University at Albany, SUNY                    FAX:  (518) 442-4767
>     1400 Washington Ave., Albany NY 12222, USA  Mobil:  (518) 210-4504
>________________________________________________________________________
>__
>


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