The concept of a norm of reaction was introduced in 1909 by Richard Woltereck as both a theoretical concept and a visual depiction to capture phenotypic plasticity: the variability of the phenotypic response of genetically identical organisms subjected to different environmental regimes. The new concept was also supposed to reconcile Mendelian variation with Darwinian selection and help resolve a sometimes virulent dispute about the nature of evolution. The norm of reaction largely disappeared from Western genetics for the next thirty years, though its use flourished in the Soviet Union until the suppression of genetics there during the Lysenko era. Repatriated to the West by Theodosius Dobzhansky in 1937, the norm of reaction began to be used sporadically in the West after 1950 and until the 1970s, when its evolutionary etiology emerged as a locus of significant theoretical research and controversy. In the 1990s molecular techniques began to be deployed to resolve the question whether reaction norms arose as a result of direct selection for genes for plasticity or whether they arose as a result of selection on other traits. Meanwhile, the precise conceptualization of the term norm of reaction went through at least three significant shifts.
The main objective of this project is to trace the history of the norm of reaction from 1909 to 1999, and to investigate why its use flourished or disappeared in different intellectual and social contexts, why its meanings shifted, and what methodological lessons can be gleaned from the controversy over its evolutionary etiology. The key questions include: (i) whether the ambient conceptual framework of genetics in different research traditions (especially in the case of Soviet evolutionary genetics) can explain these changes; (ii) if so, what intellectual and other factors (for instance, dialectical materialism) may be responsible for these ambient frameworks; (iii) whether the choice of model organisms (especially animal models instead of plants) can explain some of the mentioned changes in the popularity of the use of reaction norms; (iv) to what extent the disputes over the evolution of phenotypic plasticity and reaction norms were over substantive issues and to what extent they were methodological; (v) why specific modeling strategies (such as optimization and quantitative genetic techniques as well as explicit genetic models) were introduced, and sometimes rejected, while exploring the evolutionary etiology of reaction norms; and (vi) whether molecularization is similarly leading to shifts in the meaning and scope of the term.
Besides one paper by Raphael Falk (Hebrew University of Jerusalem) and Dr. Sarkar's preliminary work, there is almost no historical or philosophical analysis of the norm of reaction. This project seeks to remove this lacuna in the history of genetics and evolutionary biology. Dr. Sarkar intends to produce a number of historical and philosophical papers, and the results eventually will be synthesized into a book-length monograph.
