"Evolution shows that in the long run, if the superior mixes with the inferior, the product is halfway between, and inferior to what you started with in the original superior group - in other words, mongrelized."

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Evolution, thus, is merely contingent on certain processes articulated by Darwin: variation and selection. No longer is a fixed object transformed, as in transformational evolution, but an entirely new start is, so to speak, made in every generation.

— Ernst Mayr