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Re: Cladistics (was Sci. Am. - present)



>It is a pity we cannot have DNA details of dinosaurs since I  do not
>believe >there was such a sudden burst of DNA changes on loss of flight,
>as there was >of morphological changes.  I would place much greater faith
>in  a DNA cladogram >for birds and related dinos.  

I'm not sure why this is.  In the vast majority of cases, DNA sequence data
and morphology tell  you more or less the same thing.  Molecular data are
no less subject to selective pressures, and levels of homoplasy given data
sets of the same size are no different.

10 years ago, the question was "should it be molecules or morphology?"
Today, the answer is "yes!"




> Incidentally there is absolutely no reason why we cannot use a  bit of
>>brainpower to improve the performance of cladistics.  When I said
>"blind" cladistics, I did NOT mean all cladistics is blind.



How would you "improve" a parsimony analysis?  I'm not trying to be
patronizing - this is a serious question.  Given the principle of total
evidence, the hypothesis that best matches all the available data is the
preferred one - are you advocating some sort of significance test for
character data?  If so, on what objective basis would this be based?  And
bear in mind, switching to molecular data won't necessarily "improve" the
analysis, except by adding additional relevant information.



chris


=-=-=-=-=-=-=-=-=-=-=-=-=-=
Christopher Brochu

Postdoctoral Research Scientist
Department of Geology
Field Museum of Natural History
Lake Shore Drive at Roosevelt Road
Chicago, IL  60605  USA

cbrochu@fmppr.fmnh.org