Among the vast diversity of traits and genes in a population, it is possible to selectively reinforce for certain traits and have them become the dominantly present genotype in a relatively few generations. In a natural setting, the dominant color pattern of that salt-and-pepper moth in England changed from light (historically) to dark (after the industrial revolution, to match coal soot), and now back to light (much less coal being burned nowadays).

In situations with intended human intervention, this is how we got Manx cats, Chihuahua dogs, and Condello-strain BG.

"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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