A study of DNA from ancient farmers in Europe shows sharp differences from that of modern Europeans — results that are likely to add fuel to the debate over European origins. Researchers led by Wolfgang Haak of Johannes Gutenberg University in Mainz, Germany, argue that their finding supports the belief that modern residents of central Europe descended from Stone Age hunter-gatherers who were present 40,000 years ago, and not the early farmers who arrived thousands of years later. But other anthropologists questioned that conclusion, arguing that the available information isn't sufficient to support it. Haak's team used DNA from 24...