FW: A Perspective on Cope's Rule

["Wilson, Yvonne" <WilsonY@CarnegieMNH.Org>]

In response to Michael Milbocker:

> The smallest animals evolve
at one or two orders of magnitude faster pace than the largest animals.

Isn't part of the reason for needing huge litters because many fewer of the 
offspring live to sexual maturity?  Otherwise populations would be growing 
exponentially, overwhelming available resources.  If so many offspring die,  
then their rate of evolution won't keep pace with the rate of producing 
offspring. The rate of evolution wouldn't be so wildly different from that of 
larger animals.



>The subgroup that goes on to increasing size rapidly experiences
evolutionary stasis by virtue of higher sexual maturity, fewer litters and
smaller litters. 

Stasis seems like a very strong word.  It would only be a halt in size 
increase, while the critter may continue to change in a hundred other ways 
(thus retaining the diversity that you say it would lack).   Stasis ala 
Eldridge ain't happening here.  Many VP'ers fight the reality of stasis anyway 
(I don't, but many do).



>Hence, when the
inevitable extinction event occurs, the large animals lack the genetic
diversity to cope (no pun intended). 

Well, that would explain why the sauropods were so unsuccessful, correct?  ;-)
I do not accept that size is such a disadvantage.  There are numerous 
trade-offs certainly.



>I'm also suggesting that "convergent" evolution is far more
common than suspected, and results from extinction events that return life
over and over to the same perpetually underlying, fast-evolving, gene pool.

This sounds almost like recapitulation.  Are you really going there? 
OR
Can you explain yourself more clearly?



Yvonne



Yvonne Wilson
Carnegie Museum of Natural History
Section of Vertebrate Paleontology
4400 Forbes Ave
Pittsburgh, PA 15213
412-578-2463