Temporal trails of natural selection in human mitogenomes

Abstract

Mildly deleterious mutations initially contribute to the diversity of a population, but later they are selected against at high frequency and are eliminated eventually. Using over 1,500 complete human mitochondrial genomes along with those of Neanderthal and Chimpanzee, I provide empirical evidence for this prediction by tracing the footprints of natural selection over time. The results show a highly significant inverse relationship between the ratio of nonsynonymous-to-synonymous divergence (dN/dS) and the age of human haplogroups. Furthermore, this study suggests that slightly deleterious mutations constitute up to 80% of the mitochondrial amino acid replacement mutations detected in human populations and that over the last 500,000 years these mutations have been gradually removed. © The Author 2009. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved.