Plasticity, Robustness, Development and Evolution

Evolutionary biologists and epidemiologists share a concern with phenotypic variation.For evolutionary biologists such variation is what provides the raw material for selection, selection being by phenotype not by genotype.Epidemiologists focus on the short-term health consequences of phenoptypic variation rather than longer-term fitness, indexed by the probability of organisms transmitting genetic material to future generations.The recent book by Patrick Bateson and Peter Gluckman, Plasticity, Robustness, Development and Evolution, provides an opportunity to reflect upon the implications of recent evolutionary biology for epidemiology and population health.Bateson and Gluckman provide a succinct summary of their book, which centres around the notion that development is both plastic-i.e.responds to circumstances-and robust, in that it can weather environmental change.Their presentation of evolutionary and developmental biology from the joint perspective of evolutionary and biomedical science considers how epigenetic processes may underlie both plasticity and robustness, and how these deeply intertwined processes can provide the material for evolutionary change.Christopher Kuzawa reflects on the implications for medicine of the relationship between development and evolution (sometimes glossed as evo-devo): the inherent complexity of gene-environment interaction over the course of development, relevance for the developmental origins of health and disease (DOHaD) and implications for the transgenerational transmission of disease risk.He considers how the particularities of mammalian life histories may influence transgenerational effects, with attenuated effects in larger and longer-lived species, rendering direct mapping from animal models to human biology problematic.Jonathan Wells focuses on the predictive adaptive response hypothesis, which proposes that there are long-term (including transgenerational) advantages in gearing early development such that adult phenotype is optimal for the anticipated environment which will prevail during the years in which the next generation is produced.He proposes a maternal capital model, in which maternal phenotype, reflecting long-term influences stretching back to grandmaternal status, buffers short-term environmental fluctuations.Tension exists between the interests of the mother and offspring, which will be reflected in their long-term joint responses to pregnancy, with consequences for disease risk and reproductive success.George Davey Smith considers the implications of evo-devo for epidemiological research and population health practice.He maintains that there is no incompatibility between evo-devo and the logic of Mendelian genetics, with the current and justified interest in epigenetics potentially diverting attention from the power of genetic analysis to inform us about the causes and mechanisms of disease ('Mendelian randomization').Classical genetic 'pure line' experiments indicate that the quantitative influence of true epigenetic inheritance is small compared with Mendelian and shared environmental effects, and efforts to understand and prevent disease in populations should reflect this, he suggests.Finally, Bateson and Gluckman respond to the commentaries and reassert the importance of an integrated vision of how developmental and evolutionary processes impact on phenotypic trajectories, health and disease.