title: Towards a mechanistic foundation of evolutionary theory.
abstract: Most evolutionary thinking is based on the notion of fitness and related ideas such as fitness landscapes and evolutionary optima. Nevertheless, it is often unclear what fitness actually is, and its meaning often depends on the context. Here we argue that fitness should not be a basal ingredient in verbal or mathematical descriptions of evolution. Instead, we propose that evolutionary birth-death processes, in which individuals give birth and die at ever-changing rates, should be the basis of evolutionary theory, because such processes capture the fundamental events that generate evolutionary dynamics. In evolutionary birth-death processes, fitness is at best a derived quantity, and owing to the potential complexity of such processes, there is no guarantee that there is a simple scalar, such as fitness, that would describe long-term evolutionary outcomes. We discuss how evolutionary birth-death processes can provide useful perspectives on a number of central issues in evolution.
authors.affiliation: Department of Zoology and Department of Mathematics, University of British Columbia, Vancouver, Canada.
authors.forename: Michael
authors.identifier: 0000-0002-5975-5710
authors.initials: M
authors.lastname: Doebeli
authors.affiliation: Departamento de Fisica, Universidad de Santiago de Chile, Santiago, Chile.
authors.forename: Yaroslav
authors.identifier: 0000-0002-0201-3396
authors.initials: Y
authors.lastname: Ispolatov
authors.affiliation: Department of Mathematical and Statistical Sciences, University of Colorado, Denver, United States.
authors.forename: Burt
authors.initials: B
authors.lastname: Simon
mesh_terms: D005075:Biological Evolution; D056084:Genetic Fitness; D008957:Models, Genetic
keywords: adaptive dynamics; birth-death process; ecology; evolutionary biology; evolutionary theory; fitness; genomics; multi-level selection