Tracking human migration patterns through the oral bacterial flora

As modern humans (Homo sapiens) migrated out of Africa to different parts of the world, their obligate indigenous bacterial biota accompanied them. As both evolved, the accumulations of mutations in their DNA can reveal their phylogenies. Here, we describe the evolutionary history of an indigenous bacteria, Streptococcus mutans, from the oral cavity. Using several genetic markers, four distinct clusters of S. mutans genetic traits coincide with individuals of distinct geographic or racial groups comprised of two African clades and an Asian and a Caucasian clade. The evolutionary lineage of S. mutans is in agreement with anthropological artifacts marking the trail of human migrations.