GENETIC EVIDENCE FOR A PLEISTOCENE POPULATION EXPLOSION

TLDR

Population size expansions leave characteristic signatures in mitochondrial mismatch distributions, which can be used to infer historical changes in population size. The study aims to model sudden changes in female population size and estimate the timing and magnitude of such events from mitochondrial data. Statistical methods are developed to estimate θ₀ = 2uN₀, θ₁ = 2uN₁, and τ = 2ut, and to construct confidence regions for these parameters. Application of these estimators to published mitochondrial data shows they are robust to simplifying assumptions and reveals a major human population expansion during the late Pleistocene.

Abstract

Expansions of population size leave characteristic signatures in mitochondrial "mismatch distributions." Consequently, these distributions can inform us about the history of changes in population size. Here, I study a simple model of population history that assumes that, t generations before the present, a population grows (or shrinks) suddenly from female size N0 to female size N1 . Although this model is simple, it often provides an accurate description of data generated by complex population histories. I develop statistical methods that estimate θ0 = 2uN0 , θ1 = 2uN1 , and τ = 2ut (where u is the mutation rate), and place a confidence region around these estimates. These estimators are well behaved, and insensitive to simplifying assumptions. Finally, I apply these methods to published mitochondrial data, and infer that a major expansion of the human population occurred during the late Pleistocene.