Mutation, drift, migration and natural selection are all unceasing forces that drive the engine of evolution ever onward

From A Troublesome Inheritance by Nicholas Wade. Page 75.

Mutation, drift, migration and natural selection are all unceasing forces that drive the engine of evolution ever onward. Even if a population stays in the same place and its phenotype, or physical form, remains the same, its genotype, or hereditary information, will remain in constant flux, running like the Red Queen to stay in the same place.