Since the publication of Darwin's "On the Origin of Species", we have had an outline for how evolution can occur by natural selection. There must be variation in a trait between individuals, that variation must be heritable, and more individuals must be produced than can survive and reproduce. Natural selection can then act on that variation, leading to changes in population frequencies of the trait value. Theoretically, this scheme makes sense, but empirically it is difficult to observe, since evolution acts over large time scales. Enter Peter and B. Rosemary Grant.The Grants went back to Darwin's birds, the Galapagos finches, to try to peek at evolution in action. Beginning in 1976, they and their students spent months of every year in the Galapagos, measuring everything they could about the finches and their habitat. Then, between 1982 and 1983, the most extreme El Nino event in 400 years occurred, and the Grants finally got their chance. Their 1993 paper reports their findings.
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