Eugenics and individual phenotypic variation: to what extent is biology a predictive science?

Eugenics, in whatever form it may be articulated, is based on the idea that phenotypic characteristics of particular individuals can be predicted in advance. This paper argues that biology's capacity to predict many of the characteristics exhibited by an individual, especially behavioral or cognitive attributes, will always be very limited. This stems from intrinsic limitations to the methodology for relating genotypes to phenotypes, and from the nature of developmental processes which intervene between genotypes and phenotypes. While genetic studies may generate valid population predictions for conditions which impact human health, neither genetics nor developmental biology are likely to generate useful individual predictions about variation in non-disease-related human behavioral and cognitive phenotypes in the foreseeable future.