So, nitpicking on definitions, now that’s the answer.
The REAL answer is that there have no civilizations, prior to the mid-20th century, in which there was no general idea of non material beings/existence/gods/spirits/next-world.
Buddhist DO beieve in non-material entities/realities (e.g. reincarnation). Most Confucians are either Buddhists or have a nice slice of ancestor worship.