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. / Thesis / Master of Science (MSc) / Despite decades of research into menopause, there remains no clear understanding of how this deleterious trait came to persist in the human population. It has been proposed that a bias in mate choice such that only younger females are chosen to mate can result in the accumulation of deleterious mutations, ultimately leading to menopause. We analyzed the evolution of menopause under a mating system of serial monogamy by a computational simulation. We came to three main conclusions. Firstly, under modern demographic parameters, menopause cannot evolve under serial monogamy. Secondly, in a population of shortened longevity, similar to chimpanzee, menopause neutrally appears at an age presently experienced by women. Finally, when mate choice is restricted such that only young females are eligible to mate within a system of serial monogamy, menopause can evolve. This means with the current mate choice shift towards older women, menopause can be postponed or even eliminated.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22829 |
| Date | January 2018 |
| Creators | Gomes, Alyssa |
| Contributors | Singh, Rama, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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