The Shifting Meaning of Mutation

Mutatis Mutandis: The Shifting Meaning of Mutation

Luis Campos

This project centered on the shifting meaning of mutation in the early twentieth century, a remarkable shift from the phenotypic to the genotypic level that has gone relatively unanalyzed to date. The quest to discover ever-more-minute levels of evolutionarily significant variation (classical genetics) came into conflict with established practices that recognized species at the phenotypic level. Steady improvements in the fields of karyology, on the other hand, presented intermediate levels of variation the significance of which remained contested throughout at least the 1910s and 1920s and into the 1930s—were these “chromosomal mutations” (or as Albert Blakeslee once called them, “chromosomations”) or were they simply chromosomal aberrations?

Growing out of Luis Campos' earlier work on the place of shared cultural understandings of radiation in the study of heredity, the project's focus on the shifting meanings of mutations centered particularly on the work of Hugo de Vries, D.T. MacDougal, R. Ruggles Gates, and Albert F. Blakeslee, and with an eye to the later developments in cytogenetics by C.D. Darlington and Barbara McClintock. Campos was particularly interested in replacing Whiggish accounts of the death of de Vries’ mutation theory—which would hold apparent irregularities and unusual phenomena in his model organism of choice, the evening primrose Oenothera lamarckiana, responsible for the dismissal of this theory—with an account that recognizes the fundamental role studies of Oenothera played in the emergence of cytogenetics. Campos also sought to explore the reasons for the sedimentation of “mutation” as a term based on studies of point mutations in animals, rather than the other evolutionarily significant levels of variation that are common in plants—including the chromosomal dynamics of Oenothera.

A pluralistic understanding of mutation, one drawing more from botanical investigators than from the well-covered terrain of the drosophilists, does more to capture the range of practices scientists engaged in than the fly-centric, reductive, point-mutation accounts we are most familiar with. In this project, Campos sought to recover for our historiography some of these multiple meanings of mutation as important and dominant features of the study of genetics in the first half of the twentieth century.