[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: courses



>> I was talking about characters that would be used in a morphological 
cladistic analysis (which presumably would have already undergone 
selective pressure)... No direction, it's just that 
characters - as pieces of morphology - must be functional, which 
reduces the possible characters any organism can evolve (and pathways 
too). <<
 
I disagree.  Just because a feature is present in an organism, does not
mean that feature performs a function.  There's a long list of useless
features in humans and in other organisms as well, and it is _these
useless features that are the best characters on which to base
classification_.  So the best characters to use in cladistic analysis
are the ones subject to the _least_ selective pressure.  That way you
stay away from convergence.

And I actually have a quote to back this up:

" No one regards the external similarity of a mouse to a shrew, of a
dugong to a whale, of a whale to a fish, as of any importance. These
resemblances, though so intimately connected with the whole life of the
being, are ranked as merely `adaptive or analogical characters;' but to
the consideration of these resemblances we shall have to recur. It may
even be given as a general rule, that the less any part of the
organization is concerned with special habits, the more important it
becomes for classification."

(From Charles Darwin, the Origin of Species, Ch 13)

Dan