A Nutritional Basis for the Spread of Indo-European Languages

Indo-European languages are native to populations from Ireland to Afghanistan and India and, in historical times, to the Tarim Basin in China. This spread occurred within a few thousand years carried by people who were mostly horse pastoralists and who carried a mutant regulator of the lactase gene so that they could as adults digest milk sugar.  Individuals with such lactase persistence are able to extract 40% more calories from milk, while others usually ferment away the milk sugar lactose by making cheese or yogurt.  While superior technology of invaders can be adapted by indigenous people, such a biological advantage cannot be copied.