Evolutionary scientists are increasingly turning to an unusual tool to explore ancient human history: bacteria. Some microorganisms, like Helicobacter pylori, take up residence in our stomachs. Since they go where humans goand undergo genetic changes along the waythey provide a way to track ancient human migration patterns. A study by a team of international researchers, recently published in the journal Science, shows how genetic investigation of H. pylori in modern-day East Asian and Pacific people has cleared up questions about how that region of the world was first settled.