cavemen etc were not intellectually mature enough to have such concise notions of spirituality/life/DEATH/ and hence after life. im not being condescending, or trying to be. but i think they cudnt put abstract notions into such concise concepts and then extrapolate from such concepts what exactly death implied and what is existance vs non existance or a possibility of the GIVEN personal conciousness from dying. i cud be wrong though.