One of the strongest proofs for evolution is that the geological record, for all its imperfections, shows a single invariant trajectory. The oldest rocks contain only single- celled creatures. Later strata show the appearance of invertebrates. Then we see the first fishes, then amphibians, then reptiles, and finally mammals. Man appears latest on the scene. The fossils are found in exactly the places and at exactly the times that we would expect if Darwin’s theory is correct.
Not a single fossil has ever been found in a place where it is not supposed to show up. If we ever discover the fossil of a single reptile in a rock so old that fishes had not yet arrived, or if we find human skeletons at the time when dinosaurs also lived, then Darwin’s theory will be proven false and biologists will have to come up with a new one.
Until this happens—and I don’t think it will—evolution remains the best and most persuasive account of our origins. It is impossible to deny the theory’s explanatory power. Evolution by natural selection helps us to explain why pesticides and antibiotics frequently result in the pests and bacteria developing new strains more resistant to human efforts to wipe them out. In a word, they evolve.
Without evolution it would not be easy to understand features of living creatures that seem poorly designed or serve no functional purpose. We see snakes with tiny legs buried inside their skins and flightless beetleswith wings. We humans possess an unnecessary appendix. How to explain these vestigial organs? Evolution says it is because snakes, flightless beetles, and humans are all descended from creatures that needed those organs to survive.
Still, evolution remains a theory with clear limits. When Dawkins subtitles one of his books “How the Evidence of Evolution Reveals a Universe Without Design” he shows no awareness of these limits. When Dennett invokes evolution as an all-purpose explanation in cosmology psychology culture, ethics, politics, and religion, he too goes way beyond the evidence.
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