Human inhabitation of central Mexico probably began around 12,000 BCE. By the 12th century CE, various ethnicities inhabited the valley. Pre Hispanic, especially pre Aztec history of the area is scarce primarily because the Aztec destroyed many documents of the prior Tepanec Empire when they came to power. One historical document is the "Codex García Granados" from the early colonial period. It categorizes events of the Toluca Valley into three periods: the “legendary period,” the reign of Tepanac king Tezozomoc, and the Aztec period.