Evolutionary metastability

From the molecular to the geological scale, evolving populations are often seen to change by leaps and bounds rather than “steadily, slowly, and continuously”, as Darwin imagined. Such “punctuated equilibria” can be traced back to the irregular structure of fitness landscapes: depending on the mutation rate, it can take a long time for a population to cross a fitness valley (genotypic stasis) or exit a large neutral network (phenotypic stasis). In this talk I will show that punctuated equilibria may be viewed as an instance of Markovian metastability—as fluctuation-activated jumps over potential barriers. Importantly, the relevant potential is not the fitness landscape itself, but rather a mollified version of it that also includes mutational robustness as an evolutionary optimand. Evolutionary potentials enable a coarse-grained description of evolutionary dynamics in complex fitness landscapes—a prerequisite to any meaningful notion of evolutionary prediction.