It only took a few thousand years for the human ability to digest the milk sugar lactose, after infancy, to spread throughout Central Europe, a study suggests. Researchers analysed genetic material from the bones of individuals who had fallen in a conflict around 1200 BC on the banks of the Tollense, a river in present-day Germany. They found that around one in eight of the assumed warriors had a gene variant that enabled them to break down the lactose in milk. Population geneticist Professor Joachim Burger, of Johannes Gutenberg University Mainz (JGU), said: “Of the present-day population living in this same area, around 90% have this lactase persistence. “This is a huge difference when you consider that there cannot be many more than 120 human generations between then and today.” The study, published in Current Biology, found that aside from lactase persistence and a few other genetic variants, the genomes of the Tollense people are similar to those of today’s inhabitants of northern Germany and the Baltic Sea region. Professor Daniel Wegmann, of the University of Fribourg in Switzerland, said: “The only way to explain this difference between these Bronze Age people and those of today is very strong natural selection.