How the Choice of Model Phenomena Matters: Pigmentation and the Conceptualization of Gene Action in Early Genetics

Much has been said about how the choice of experimental organisms matters, how they open possibilities and impose constraints on a research program and often push an inquiry in an unexpected direction. The same might be said about the kinds of phenomena researchers come to study as representative of a broader class of phenomena. Geneticists in the early twentieth century studied many characters to understand the patterns of heredity and their underlying cytological basis. Nonetheless, the color of flowers, seeds, or other parts of plants, as well as the color of fur and eyes in animals, were particularly prominent objects of study. Some researchers relied entirely on the phenomena of pigmentation in their projects; others worked with many characters but used the inheritance of color as a prime example in theoretical considerations. Most interestingly, the focus on pigmentation afforded possibilities for interfield transfer and collaboration between genetics and organic chemistry. In that way, it played an important role in shaping the conceptualization of gene action in early genetics. I will follow pigmentation as a research object in genetics from early Mendelian debates to the work of Beadle and Ephrussi in the US and France, and Kühn, Caspari, and Butenandt in Germany.