About 600 million people around the world live with whipworms. Most are children in the developing world, whose physical and mental development is stunted by these gastrointestinal parasites. The whipworms affect their ability to learn and therefore have a long-term impact on the social and economic situations of some of the world's poorest people. Although the whipworm species Trichuris trichiura is known to inhabit both non-human primates and humans, little is known about the parasite. Indeed, until a recent study by Ria Ghai, a doctoral student in biology at McGill, it was widely assumed that a single species was capable of infecting both primates and humans. But Ghai has discovered that there are three genetically distinct groups of whipworms.