In the early 1900s, scientists discovered that each person belonged to one of four blood types. Now they have discovered a new way to classify humanity: by bacteria. Each human being is host to thousands of different species of microbes. Yet a group of scientists now report just three distinct ecosystems in the guts of people they have studied.
Far from being a bad thing, these are the very bacteria that help us digest foods, and stay free of bad bacteria and disease.
Read the full article here: New York Times - Bacterial Ecosystems Divide People into Three Groups Scientists Say