Our distant past has revealed clues to that bad feeling in your gut

New research has shed light on the mysterious past of a common bacteria that infects more than half the world’s population, and suggests how it became so pervasive.

Helicobacter pylori, also known as H. pylori, is a very successful pathogen that makes its home in the human digestive tract and stomach. It is commonly found in people from Africa to Europe and in the Middle East. Once established, it can lead to chronic conditions like gastritis and stomach ulcers, and in some cases, stomach cancer.