Recent developments in human organ transplantation have created an interest in the cultural meanings of transplantation. The problem of identity is manifest in the case of a face transplant, but in principle pertains to transplantation of other organs as well. Fundamental to these concerns is an understanding of the meaning of identity for a part and therefore what exactly is being transplanted. The contours of this problem were explored in the ancient and medieval thought experiment of the boat that is replaced piecemeal over a period of time, but in these discussions, identity was directly associated with the physicality of the parts and the relationship between the identities of parts and the identity of the whole. Absent from them is consideration of the functions of the parts and implicitly also the relationship between function and identity. This way of framing the problem of transplantation and identity persists today in considerations of human transplantation. While individual recipients may claim to experience unfamiliar dreams or other affects that they attribute to a transplanted organ and its donor, the scientific world regards the functions of these transplanted parts in terms of homologies and physico-chemical processes. Consideration of functions are in this sense structure-specific, not specific to the individual part as a unique identity. Indeed, the assumption of homology is crucial to the logic of transplantation–one can restore a function by swapping out a dysfunctional part for a functional one. Considerations of individual identities are thus considerations of structures.
Transplantation of functions, however, is fundamental to knowledge-making in the biological science of chronobiology, which comprehends the temporal nature of living substances generally, but more specifically the study of biological rhythms. In this paper I will explore the historical development of the idea that timing is a component of identity–definitive of function and thus behavior–and document the transplantation of timing structures (biological clockworks) as a basic research methodology for investigating the ontology of biological rhythms. The major historical period under consideration will be the decades beginning with surgical transplantation of timing structures in 1950s England and culminating with the successful splicing of DNA segments to elucidate cellular timing mechanisms in the 1980s and 1990s.