On age-specific selection and extensive lifespan beyond menopause.

Tin Yau Pang

doi:10.1098/rsos.191972

Abstract

Standard evolutionary theory of ageing predicts weaker purifying selection on genes critical to later life stages. Prolonged post-reproductive lifespan (PPRLS), observed only in a few species like humans, is likely a result of disparate relaxation of purifying selection on survival and reproduction in late life stages. While the exact origin of PPRLS is under debate, many researchers agree on hypotheses like mother-care and grandmother-care, which ascribe PPRLS to investment into future generations—provision to one’s descendants to enhance their overall reproductive success. Here, we simulate an agent-based model, which properly accounts for age-specific selection, to examine how different investment strategies affect the strength of purifying selection on survival and reproduction. We observed in the simulations that investment strategies that allow a female individual to remain contributive to its own descendants (infants and adults) at late life stages may lead to differential relaxation of selection on survival and reproduction, and incur the adaptive evolution of PPRLS.

Highlights

The theory of evolution posits that natural selection favours the traits that enhance one’s reproductive success, which depends on how frequently one reproduces and on time and effort invested into the future generations [1]
If we properly account for the effects of ageing, post-reproductive lifespan (PPRLS) emerges under some of the investment strategies
We introduced a modelling framework that can account for the deleterious nature of mutation, and quantify age-specific selection on survival and reproduction, and it is suitable for investigating the effects of ageing

Summary

Introduction

The theory of evolution posits that natural selection favours the traits that enhance one’s reproductive success, which depends on how frequently one reproduces and on time and effort invested into the future generations [1]. The evolutionary theory of ageing further predicts differential selection at different stages of life. Because old individuals have lower overall reproductive output and lower survival prospect than young ones, the strength of selection on age-specific loci weakens with increasing age. There are a few exceptions, such as humans and resident killer whales, whose female individuals experience prolonged post-reproductive lifespan (PPRLS), i.e. a royalsocietypublishing.org/journal/rsos R.

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Conclusion