Perspectives on human health and disease from evolutionary and behavioral ecology

Phenotypic plasticity refers to variation in the phenotype that can be attributed to environmental differences rather than genetic differences (WestEberhard 2003); this definition does not, however, invoke the false dichotomy of ‘nature versus nurture.’ Nor does it mean that learning and other phenotypically plastic traits require less genetically transmitted information than do more canalized traits. The same genotype can lead to different phenotypes in different environments, but genes nonetheless play a role in the development of phenotypically plastic traits. Unpredictable and heterogeneous environments select for traits that have a high degree of phenotypic plasticity, whereas stable environments lead to more canalized development. Phenotypic plasticity can be adaptive because it tends to generate a better fit between the organism and the environment. As noted by Alexander (1979: 90), all organisms are to a greater or lesser degree phenotypically variable in ways that enhanced reproduction in the different environments to which they were typically exposed in the past and ‘such plasticity is almost the definition of phenotype.’ Introduction