Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals. This is accomplished by considering the geographic distribution of individuals in light of genetics, particularly population genetics. This term was introduced to describe geographically structured genetic signals within and among species. An explicit focus on a species' biogeography/biogeographical past sets phylogeography apart from classical population genetics and phylogenetic. Past events that can be inferred include population expansion, population bottlenecks, vicariance and migration. Recently developed approaches integrating coalescent theory, or the genealogical history of alleles and distributional information can more accurately address the relative roles of these different historical forces in shaping current patterns.