Buddhism has existed in Cambodia since at least the 5th century AD, with some sources placing its origin as early as the 3rd century BC. Buddhism is the official religion of Cambodia. Approximately 97% of Cambodia's population follows Theravada Buddhism, with Islam, Christianity, and tribal animism making up the bulk of the small remainder. The wat (Buddhist monastery) and Sangha (monkhood), together with essential Buddhist doctrines such as reincarnation and the accumulation of merit, are at the centre of religious life, but interact with indigenous beliefs such as the central role of ancestors and spirits.