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ten thousand years old. If that were the case, we’d be able to stand on the west coast of Spain and see the skyline of New York City, for Europe and America would have moved less than a mile apart!)
    When Darwin wrote The Origin, most Western scientists, and nearly everyone else, were creationists. While they might not have accepted every detail of the story laid out in Genesis, most thought that life had been created pretty much in its present form, designed by an omnipotent creator, and had not changed since. In The Origin, Darwin provided an alternative hypothesis for the development, diversification, and design of life. Much of that book presents evidence that not only supports evolution but at the same time refutes creationism. In Darwin’s day, the evidence for his theories was compelling but not completely decisive. We can say, then, that evolution was a theory (albeit a strongly supported one) when first proposed by Darwin, and since 1859 has graduated to “facthood” as more and more supporting evidence has piled up. Evolution is still called a “theory,” just like the theory of gravity, but it’s a theory that is also a fact.
    So how do we test evolutionary theory against the still popular alternative view that life was created and remained unchanged thereafter? There are actually two kinds of evidence. The first comes from using the six tenets of Darwinism to make testable predictions. By predictions, I don’t mean that Darwinism can predict how things will evolve in the future. Rather, it predicts what we should find in living or ancient species when we study them. Here are some evolutionary predictions:
    • Since there are fossil remains of ancient life, we should be able to find some evidence for evolutionary change in the fossil record. The deepest (and oldest) layers of rock would contain the fossils of more primitive species, and some fossils should become more complex as the layers of rock become younger, with organisms resembling present-day species found in the most recent layers. And we should be able to see some species changing over time, forming lineages showing “descent with modification” (adaptation).
    • We should be able to find some cases of speciation in the fossil record, with one line of descent dividing into two or more. And we should be able to find new species forming in the wild.
    • We should be able to find examples of species that link together major groups suspected to have common ancestry, like birds with reptiles and fish with amphibians. Moreover, these “missing links” (more aptly called “transitional forms”) should occur in layers of rock that date to the time when the groups are supposed to have diverged.
    • We should expect that species show genetic variation for many traits (otherwise there would be no possibility of evolution happening).
    • Imperfection is the mark of evolution, not of conscious design. We should then be able to find cases of imperfect adaptation, in which evolution has not been able to achieve the same degree of optimality as would a creator.
    • We should be able to see natural selection acting in the wild.
     
     
    In addition to these predictions, Darwinism can also be supported by what I call retrodictions: facts and data that aren’t necessarily predicted by the theory of evolution but make sense only in light of the theory of evolution. Retrodictions are a valid way to do science: some of the evidence supporting plate tectonics, for example, came only after scientists learned to read ancient changes in the direction of the earth’s magnetic field from patterns of rocks on the seafloor. Some of the retrodictions that support evolution (as opposed to special creation) include patterns of species distribution on the earth’s surface, peculiarities of how organisms develop from embryos, and the existence of vestigial features that are of no apparent use. These are the subjects of chapters 3 and 4.
    Evolutionary theory, then,