When Mexican police found a pile of about 150 skulls in a cave near the Guatemalan border, they thought they were looking at a crime scene, and took the bones to the state capital. It turns out it was a very cold case. It took a decade of tests and analysis to determine the skulls were from sacrificial victims killed between A.D. 900 and 1200, the National Institute of Anthropology and History said Wednesday. Frontera Comalapa in southern Chiapas state has long been plagued by violence and immigrant trafficking. And pre-Hispanic skull piles in Mexico usually show a hole bashed...