The ability for humans to digest milk as adults has altered our dietary habits and societies for centuries. But when and how that ability—known as lactase persistence or lactose tolerance—occurred and became established is up for debate. By testing the genetic material from the bones of people who died during a Bronze Age battle around 1,200 BC, an international team of scientists including Krishna Veeramah, Ph.D., of Stony Brook University, suggest that lactase persistence spread throughout Central Europe in only a few thousand years, an extremely fast transformation compared to most evolutionary changes seen in humans. Their findings are published in Current Biology.