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Re: "Cope's Rule" Put to the Test

> If it is, then it appears to me that "Cope's Law" is an interesting but
> ultimately unuseful generalized observation, for two reasons.  First,
> most tetrapod clades start out small and get bigger because in general,
> only smaller tetrapod animals survive mass extinctions and re-radiate
> into new lineages.  Second, if evolution is an ultimately unguided
> process, then each lineage will have its own selective reason for
> getting bigger (or smaller) over evolutionary time, and there's no valid
> grounds for extrapolating trends across lineages.  
> Maybe I'm missing something (always very possible), but I keep getting
> this image of somebody somewhere looking at a series of theropod fossils
> and saying, "why did these theropods get bigger over time?  Must be
> Cope's rule at work." and leaving it at that.  

     As I understand it, "Cope's Law" is an observation, not an
explanation for the observation.  In other words "Cope's Law" says
"tetrapods tend to get larger with time more often then they tend to get 
smaller", and the above statements provide an explantion of how Cope's Law
might work.       

LN Jeff