“In the beginning, there were bacteria.... [A] nearly universal assumption is that all subsequent life descended from the original life form through a continuous chain of ancestor-descendant pairs. This assumption looks good because all living organisms share biochemical traits. It is conceivable, of course, that life originated more than once on the early earth but that all except one life form died out early, leaving a single lineage as the ancestor of life as we know it. If this did happen, it was the first important species extinction.” IfsKnowsFirstsLooksImportantHappensEarthFormCoursesShareUniversalDiedOriginalsSpeciesLeavingChainsAssumptionPairsAncestorTraitsOrganismsExtinctionDescendantsBacteriaLineageLiving OrganismsSpecies Extinction Author:David M. Raup
“Now let me step back from the problem and very generally discuss natural selection and what we know about it. I think it is safe to say that we know for sure that natural selection, as a process, does work. There is a mountain of experimental and observational evidence, much of it predating genetics, which shows that natural selection as a biological process works.” ThinkingKnowsDoeShowsProblemProcessNaturalStepsSafeMountainEvidenceLet MeSelectionGeneticsNatural Selection Author:David M. Raup
