GENETIC EVIDENCE FOR A PLEISTOCENE POPULATION EXPLOSION

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.