GENETIC-EVIDENCE FOR A PLEISTOCENE POPULATION EXPLOSION

Expansions of population size leave characteristic signatures in mitoc hondrial ''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 gene rations before the present, a population grows (or shrinks) suddenly f rom female size N-0 to female size N-1. Although this model is simple, it often provides an accurate description of data generated by comple x population histories. I develop statistical methods that estimate th eta(0) = 2uN(0), theta(1) = 2uN(1), and tau = 2ut (where u is the muta tion rate), and place a confidence region around these estimates. Thes e estimators are well behaved, and insensitive to simplifying assumpti ons. Finally, I apply these methods to published mitochondrial data, a nd infer that a major expansion of the human population occurred durin g the late Pleistocene.