ABSTRACT
This chapter provides a broad overview of the evidence for genetic adaptation of particular traits to different environments, and also provides examples to discuss in depth, reflecting adaptation to changes in climate, altitude, and diet. It begins an exploration of the phenotypic diversity of modern human populations from an evolutionary genetic perspective. The chapter discusses the genetic bases of phenotypic variation among normal healthy people, but will point out how these may influence the risk of pathogenic consequences. Before discussing phenotypic variation, one needs to distinguish between a number of different underlying mechanisms. First, there are physiological mechanisms representing short-term and sometimes rapidly reversible responses to environmental change, known as acclimatization. Second, there is developmental plasticity, in which the environment influences the long-term development of an individual. Finally, there are genetic mechanisms directly responsible for phenotypic variation.
