The prehistory and history of Kentucky span thousands of years, and have been influenced by the state's diverse geography and central location. Based on evidence in other regions, it is likely that the human history of Kentucky began sometime before 10,000 BCE. A gradual transition began from a hunter-gatherer economy to agriculture c. 1800 BCE. Around 900 CE, the Mississippian culture took root in western and central Kentucky; the Fort Ancient culture appeared in eastern Kentucky. Although they had many similarities, the Fort Ancient culture lacked the Mississippian's distinctive, ceremonial earthen mounds.