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FW: A Perspective on Cope's Rule

Jaime Headden wrote:

>   Cope's Rule predicts that a trend to increase size is present in
> biology, and in a lineage, smaller animals will tend to become larger. 
> But
> it is possible this is a selection bias. We will tend to find larger
> animals because of the access to larger animals than smaller in an 
> area,
> given the ecology of Ngorogoro Crater or the exposure at Como Bluff. 
> Thus
> we will more easily see larger animals and a replacement over smaller
> animals because of the access to smaller animals will be less obvious 
> or
> less inherent in fact.

But, Jaime, seeing a Replacement doesn't make sense to me.  If you are 
considering the collecting bias toward larger animals, you will always have 
that bias present.  Thus you will not see a transition from smaller to larger, 
just the largest animals present at any given time.  Any sample, older or 
younger, would only have big specimens.   

If I'm misunderstanding you, please clarify.

Happy to chew on bias possibilities,

Yvonne Wilson
Carnegie Museum of Natural History
Section of Vertebrate Paleontology
4400 Forbes Ave
Pittsburgh, PA 15213