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On the T.rex forelimbs as toothpicks scenario:
Cute, but remember:
1) Keep in mind the phylogenetic nature of the forelimbs. The ancestral
condition of the forelimbs has alot of influence on what they are used for
later (a change of usage would create a co-opted condition (i.e. an
exaptation vs. an adaptation), as in bird wings from theropod forelimbs).
2) Definitely, absolutely, positively remember that nothing needs a use
necessarily. Looking at a structure and asking "Why?" is one of the
toughest questions in paleontology. You have the aforementioned
phylogenetic issue, allometric processes, other non-adaptive
characteristics, and then a whole messy web of adaptive processes that
combine somehow to create the structure. In every case the relative
influence of different processes is variable. Yeah, it's not satisfying
really, but it just shows how weird and wonderful evolution is, and helps
explain why those creationists can't (or won't) understand us.
John R. Hutchinson
Evolving Evolutionary Biologist
Department of Integrative Biology
University of California - Berkeley
Berkeley, CA 94720
Check out the continually evolving exhibits at the UC Museum of Paleontology!