Path dependence and historical contingency in biology

Abstract

As Smith & Morowitz (1982) once aptly wrote, biology is a discipline ‘between history and physics’. On one hand, we do have laws in biology, on top of those coming from physics and chemistry. The model system of population genetics is not very different from laws of theoretical physics, except that it contains more variables and parameters. In mechanics we must know the mass of objects, some key forces and the gravitational constant: in population genetics we must know about population size, allele frequencies, linkage, mutation and migration rates, selection coefficients and so on. But this could still be regarded as ‘ordinary’ theoretical science, albeit a bit complicated. On the other hand the laws (or rules, if we are more modest) of population genetics are of the ‘if A, then B’ nature, and often there is nothing within the theory that could decide whether A in fact holds or not. That decision comes from physics, chemistry, or - crucially for our present enquiry - history.