Investigation of the Role of Mate Choice in the Evolution of Menopause under Serial Monogamy

Abstract

Menopause, the cessation of reproductive capabilities before death, is a detrimental trait for female fitness, yet persists in all human populations. Numerous hypotheses have been published to describe how menopause has been maintained but failed to explain the origin and genetic basis of this trait. In 2013, Morton et al. proposed an influence of the mate choice behaviour, specifically a bias in mating ages that could allow for a trait, seemingly detrimental to fitness, to become neutrally fixed in a population. The goal of our research, presented herein, is to understand the role of the mating system, the sexual behaviour of a group, and especially mate choice, on the origin and evolution of menopause under a serial monogamy scenario. Analysis was conducted using an agent-based computational model that simulated populations. The populations were generated according to specified demographic parameters and reproduced according to a serial monogamy mating system. With the model, parameters were investigated including population lifespan, fecundity, pairing eligibility, age of loss of fecundity, and timing of decay in fecundity. Simulations revealed that, under certain restrictions, menopause can neutrally evolve. When mate choice was restricted to a particular age preference bias, menopause can appear with no diminishment of fitness. This novel mode for the origin of menopause is inferred to result from the accumulation of deleterious mutations in the female genome. By combining this ability of fertility-diminishing mutations to accumulate with research into the genetic basis of menopause, we provide a system for the evolution of menopause in a population of serial monogamy.