Something was amiss at the ruins of Iglesia Colorada, an ancient Incan village in the foothills of the Andes. In the remains of what had been a garbage dump, among ancient food scraps and shards of discarded pottery, researchers discovered four skulls. No bodies, no formal burial, no jewelry to carry on to an afterlife — just the skulls. No one knew why they were there. For over 15 years, since the skulls were uncovered in 2003, the mystery has baffled archaeologists. But two researchers at the National Museum of Natural History in Santiago, Chile, have proposed an explanation: The...