Re-examining heritability: genetics, life history and plasticity.

Human life-history traits (growth, maturation, nutritional status) are increasingly associated with risk of chronic degenerative disease. Twin studies suggest high heritability of such traits; however, although sophisticated approaches have identified genetic variation underlying a proportion of this heritability, studies also increasingly demonstrate significant plasticity, and many life-history traits are able to change by one standard deviation (SD) over 3-6 generations. Developments in our understanding of the contributions of genetics and plasticity to human life history are likely to improve understanding of the growing burden of chronic diseases. We argue that a life-history approach to understanding variation in the human phenotype must integrate these two risk components, and highlight the important contribution of plasticity to changes in disease prevalence.