Accelerated Drift in Age Structured Populations: Implications for Mutation Accumulation

Abstract Modern, industrial populations have demographic parameters that differ considerably from those of non-industrialised, ‘traditional’ or ‘hunter-gatherer’ populations, as well as ancestral populations. In other words, modern industrial populations have undergone a demographic transition. In this work we consider the implications of such a transition for Homo sapiens, which corresponds to a decrease in both birth and death rates, with one consequence of this transition being an increase in population size. Taking explicit account of the decreasing size of successive age-classes (e.g., fewer 50-year old females than 40-year-old females) provides useful insight into how small a genetic sample the elderly age-classes can be. The decrease of size of successive age-classes has implications for diseases of old-age, via the mode of mutation accumulation, and indicates how influential demographic transitions can be, beyond expectations based solely upon estimates of Ne. The results of simulations we present suggest that the genetic background of current laboratory model organisms, that are employed in research into age-related human diseases, may be unrepresentative of human populations and we propose that demographically transitioned captive species may provide more realistic insights into the underlying mechanisms.