The burying and reverence for the dead doesn't necessarily imply anything spiritual. The truest belief, and demonstrable, were the Sun worshippers, and where we do actually rely on such for our existence. All the various other aspects of religious belief has mostly been an evolution as to such, with a reasonably logical conclusion as to one 'something' possibly being the cause of existence. All the rest - many tales, some truth, and a lot of woo - which has happened equally in the history of science and much else..