GRANADA, SPAIN—Researchers from the University of Granada have shown that the shrinking of the teeth of primates from the genus Homo is linked to their increase in brain size, even though a growing brain would require more food. “We have established that they are two opposing evolutionary trends that have been linked for 2.5 million years, when our first ancestors within the Homo genus first appeared on the evolutionary stage,” Juan Manuel Jiménez Arenas told Science Daily. Arenas credits higher amounts of animal food in the diet for the increase in brain size, which in turn fostered social and cultural development.