Learning can influence evolutionary change in a number of ways. First, if the environment changes, learning may allow a population of individuals adapted to the old environment to persist until adaptations to the new environment evolve. This assertion implies that animals can learn to cope with challenges different than those the population evolved to meet. In fact, learning does often enable individuals to solve novel problems (as evidenced by numerous examples of animals learning to coexist with humans and even to flourish in novel urban environments). Once a population has a 'foot in the door' in a new environment, its members may evolve to learn the new behavior faster or to express the behavior congeni-tally. Simultaneously, selection may favor morphology, physiology, or biochemistry that is suited to the new environment. These new morphological/physiological/ biochemical traits must add something beyond what is afforded by the learned behavior and existing traits. Otherwise, learning can actually retard their modification. For example, if learning enables an animal to utilize a new resource perfectly well with its existing morphology, there may be little or no selection to alter that morphology.
Learning can also facilitate evolutionary change in morphological, physiological, or biochemical traits by promoting adaptive linkages among such traits. For example, a genetic variant in bill morphology in a population of birds may learn to exploit food types to which the bill is best suited, food types which are different than those exploited by individuals with different jaw morphology. The new diet will select for gut physiology appropriate to the diet. In this way, gut physiology and jaw morphology may evolve as correlated traits. Such correlated traits can greatly accelerate adaptation to the new resource and rapidly drive genetic differentiation within and among populations.
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