Accelerated Drift in Age Structured Populations: Implications for Mutation Accumulation

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 N e . 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.