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A key question for evolution has always been: How does biological variation arise? Darwin’s theory of evolution explained that natural selection killed off the less-fit variations, but how did the variation arise in the first place? In the nineteenth century the mechanisms of biological variation were not well understood and it was possible to imagine a sort of simple, perturbing force at work which gradually altered designs. This model did not match up very well with what Gregor Mendel was discovering about change in pea plants. About the same time that Darwin was working on revisions to his book Mendel was uncovering the fundamental laws of genetics. But Mendelian genetics would call for discrete jumps in biological variation rather than gradual modifications. It would take much work but about half a century later Mendel’s findings were integrated with Darwin’s theory of evolution. This neo-Darwinism was thought to be a great advance. Was not the poorly understood source of biological variation now revealed and reconciled with Darwin’s theory? But the neo-Darwinists had turned a blind eye to the elephant that was now in the room: Evolution now required a complex Mendelian machine to generate the needed biological variation. Read more