Historicizing the homology problem

Abstract

There is widespread agreement that “homology” designates something of fundamental biological importance, but no consensus as to how precisely that “something” should be defined, recognized, or theorized. Philosophical observers of this situation commonly focus on tensions between historical and mechanistic explications of homological sameness by appeal, respectively, to common ancestry and shared developmental resources. This paper uses select historical episodes to decenter those tensions and challenge standard narratives about how they arose. Haas and Simpson (1946) influentially defined “homology” simply as “similarity due to common ancestry.” They claimed historical precedent in Lankester (1870) but seriously oversimplified his views in the process. Lankester did prioritize common ancestry, but he also raised mechanistic questions that resonate with contemporary evo devo work on homology. The rise of genetics inspired similar speculations in twentieth-century workers like Boyden (1943), a zoologist who engaged Simpson in a 15-year debate over homology. Though he shared Simpson's devotion to taxonomy and his interest in evolutionary history, he favored a more operational and less theoretical homology concept. Their dispute is poorly captured by current analyses of the homology problem. It calls for further study of the complex relationship between concepts and the epistemic goals they serve.