The Cahokia Mounds outside St. Louis are the remains of one of North America’s largest indigenous population. Many archaeologists estimate that at its peak around the year 1100, Cahokia housed 10,000 to 20,000 people, with up to 50,000 inhabitants living in the surrounding area—a population size rivalling or surpassing concurrent European cities. But archaeologists are not sure how they were able to feed all of those people because their original studies indicated that they ate mostly corn, squash and beans. Now a new look at the evidence indicates that the archaeologists may have missed the presence of a lot of smaller grains like marsh elder because they used a sieve for sifting through the ruins that had too large an opening to catch the smaller grains. This article from Atlas Obscura looks at the new evidence and discusses what it tells us about MesoAmerican farmers.