The dynamics of cohort selection

The dynamics of cohort selection in age-structured populations is explored in a series of computer simulations using a single-locus two-allele model. Cohort selection is a directional process which is a consequence of genetically determined inter-cohort variation in the magnitude of expression of interference behavior; its essential premise is that all genotypes of a given age are equally susceptible to interference and that no advantage accrues to the interfering genotype. In these simulations, allele frequency, population size, intensity of interference, and reproductive apportionment are all major determinants of evolutionary rates. The generality of this process is demonstrated and an analysis of the observed frequency-dependent effects is presented. Cohort selection is distinct from other kinds of selection and may be an important cause of the persistence of interference behavior (culminating in acts of spite) within animal populations.