In the early 1980s, Luis Alvarez and his colleagues added a new dimension to Darwin's theory of evolution. With evidence from studies of the earth's crust between the cretacious and tertiary layers, they postulated that the traditional slow, gradual mutation of species over eons was also punctuated with occasional major changes, often catastrophic, that caused leaps in evolution in relatively short “moments” of history. The extinction of the dinosaurs and half the other animal species alive between the cretacious and tertiary periods of earth's history was one such momentous change, forever altering the evolution of animal species.
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