In a message dated 96-01-31 02:49:11 EST, pharrinj@PLU.edu (Nicholas J. Pharris) writes: >The *most* active fish (sharks, tuna, sailfish) have evolved some level >of endothermy. :-) > > Right. But the endothermy surely came later. We're talking about _necessity_ here. Endothermy should be considered an evolutionary improvement to an already active lifestyle.