You put three facts together - that all organisms produce more offspring that can survive, that there's variation among organisms, and that at least some of that variation is inherited - and the syllogistic inference is natural selection.
Stephen Jay GouldAlways be suspicious of conclusions that reinforce uncritical hope and follow comforting traditions of Western thought.
Stephen Jay GouldLife is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress.
Stephen Jay Gould... many folks take them seriously because they just 'know' that evolution can never be seen in the immediate here and now. In fact, a precisely opposite situation prevails: biologists have documented a veritable glut of cases for rapid and eminently measurable evolution on timescales of years and decades.
Stephen Jay Gould