Re: synapomorphies not created equal

["Tim Williams" <twilliams_alpha@hotmail.com>]

Ken Kinman wrote:

>      I've been thinking very hard about this, and I am still not convinced
> that all synapomorphies are created equal.  Some are "stronger" than others
> no matter how long or big the evolutionary gap happens to be in which it 
> falls.

This is a slippery slope - and I'm quite frightened of what might lie at the 
bottom of it.

I can foresee such an approach leading to a situation in which characters 
are assessed as "strong" or "weak" according to how they fit a given 
evolutionary scenario.  Like: "I'm convinced tyrannosaurids evolved from 
secondarily flightless birds, so any characters that contradict this 
interpretation are weak because they are obviously giving a misleading 
signal."  (This is just an example; no malice is intended toward those who 
actually hold the view that tyrannosaurids evolved from secondarily 
flightless birds.)

The only anatomical characters I can see being justifiably termed as "weak" 
are those which (for some reason) appear to be non-independent of other 
characters.  Some of these are in the process of being weeded out.  
Currently, there's a lot of solid research going on to uncover the molecular 
and development bases behind the expression of mammalian teeth.  Certain 
dental traits that have been traditionally coded separately in cladistic 
analyses may really be iterations of a single character expressed down the 
entire tooth row.

Now, if only InGen would hand over some of that dinosaur DNA of theirs we 
could do some *really* fun stuff...



Tim

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