Behavior and the Dynamic Genome

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Science  03 Jun 2011:
Vol. 332, Issue 6034, pp. 1161-1162
DOI: 10.1126/science.1203295

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When circumstances change, an organism's first response is often behavioral. But how does adaptive behavior evolve, given that it requires constant and often instantaneous interactions between an individual and its environment? The dominant view emphasizes new random DNA mutation as the starting point. This may lead to behavioral variation. If the resulting variants have different fitness values, then natural selection could result in behavioral evolution through changes in allele frequencies across generations. An alternative theory proposes environmentally induced change in an organism's behavior as the starting point (1), and “phenotypic plasticity” that is inherited across generations through an unspecified process of “genetic assimilation” (2). Despite numerous examples (3), the latter as a driver of behavioral evolution has never been widely accepted, perhaps as a reaction against Lamarckianism—the idea that characteristics acquired by habit, use, or disuse can be passed on across generations. However, behavioral genetics and genomics, especially for animals in natural populations, lend some plausibility to the phenotypic plasticity view.