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"Logic of Cladistics"

Jeff Thorne thorne at stat.ncsu.edu
Fri Jun 10 21:27:32 EST 1994

>Realistic evolutionary models tend to be 
>multivariate stochastic processes that defy analytical solution, and closed 
>form expressions for the character state distributions (i.e., distribution 
>functions or probability density functions) are generally unavailable. 

The knowledge that a statistical model differs from reality is not unique
to phylogenetics.  You will find that is true for virtually every
application of parametric statistics.  If we believed that a model was
perfect, we might call it "reality."  The more pertinent issue
is robustness.  How do violations of the (implicit or explicit)
model affect the inferences?  The hope is to gradually improve
the understanding of evolution by testing assumptions and, if
justified, replacing them. 

>        It is very telling that so few professional statisticians have 
>ventured into the phylogenetics controversy (compare this with the field of 
>theoretical population genetics which has attracted some of the most 
>brilliant probabilists of this century: Bartlett, Feller, Karlin, Kolmogorov 
>and Moran to name only a few). 

There is no doubt that there have been and continue to be many
brilliant population geneticists.  It should be realized though
that the  "phylogenies from sequence data" field is much younger.
How many of the above population geneticists were appreciated five
decades ago?  We should get back to this in fifty years.

Jeff Thorne, Program in Statistical Genetics
North Carolina State University

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