by Nicola Bertoldi
The problem addressed in this paper concerns the epistemology of chronobiology, i.e. the study of biological rhythms,... more
The problem addressed in this paper concerns the epistemology of chronobiology, i.e. the study of biological rhythms, especially circadian ones, and their influence on organisms and ecosystems. I take this particular field of biology to be an instance of a scientific paradigm with two largely complementary concepts at its roots : the concepts of “program” (especially “genetic program”) and of “mechanism”. My analysis argues the case for this paradigm having emerged in the field of molecular biology, as a result of the interplay between biologists, physicists and philosophers. Hence, this paper defines it “the molecular paradigm”.
The first part of my work tracks the evolution of the concept of “genetic program” along a period stretching from the seminal work of Erwin Schrödinger (What is life ?) to the later writings of Jacques Monod and François Jacob. I argue as well that this concept is deeply connected to the notion of “mechanism” and that this special relation has been brought out in the last thirty years by a host of philosophical analyses, focusing mainly on molecular biology and neurobiology. These works have thus set a new trend in contemporary philosophy of science, “new mechanistic philosophy”, whose main concern is to describe and asses the way practicing biologists try to detect mechanisms and explain their workings.
The second part argues that chronobiology has assimilated this paradigm, thereby conceiving the study of biological rhythms as the search for molecular clocks. This claim is supported by the analysis of some founding papers in this field, like the one of Colin Pittendrigh on the existence of “free running” circadian rhythms in insects and microorganisms. To substantiate further my point, I review a paper of William Bechtel and Adele Abrahamsen, who account for the discovery of drosophila's “clock gene” per, located in some neurons of the Suprachiasmatic Nucleus (SCN), and of the corresponding system of regulation through a negative feedback loop in fully mechanical terms. I contend that this account is no more tenable, since the complex function of this gene cannot be reduced to the interaction of a cluster of independent mechanisms. Then, alternative accounts must be taken into consideration, such as the one of Denis Noble and the one of Pierre Bailly, Giuseppe Longo, Mael Montevil, the latter proposing to represent biological time not as an oscillatory pattern, but by use of a two-dimensional geometrical model. The paper interprets this model on a philosophical background that extensively draws on the tradition of french “historical
epistemology”, as well as on the “biological thought” of Immanuel Kant. Concerning the latter one the paper aims to highlight the link between his reflexions on finality and organization in the living world and the emergence of new trends in the biology of his time, such as the embryological theory of Caspar Friedrich Wolff. In doing so, the argument turns to the studies of Philippe Huneman, in order to show how Kant connects three fundamental concepts – finality, self organisation and contingence – in a coherent conception of the organism. This short detour into kantian philosophy proves useful to the paper's last conclusions, via the concept of “organisational closure” introduced by Matteo Mossio and Alvaro Moreno. In these conclusions, I propose a radically new conceptual interpretation of biological rhythms, not as properties of biological clocks, but as properties of “temporally closed systems”.
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