Gradual evolution and species discrimination in the fossil record.

If species actually arise abruptly and persist for much longer periods essentially unchanged (punctuated equilibria), discrimination of paleontological species should be a relatively simple matter. Alternatively, if there is continuous change wihtin and between successive species (gradualism), species boundaries would be nebulous, and would have to be imposed arbitrarily. We summarize our study of omomyid primates and cite other supportive evidence which suggests that, where the record is sufficiently dense, gradual evolution (requiring arbitrary boundaries) is common between species and even genera.-from Authors primates