I believe that the idea of a after-life came rather late in the development of religion. Even the idea of the "soul" was a late development.
Provocative but extremely terse. How late is late? Could you give a brief outline of your theory of the development of religion? Do you think Homo Erectus was religious? Neanderthal? early Sapiens?
I think the experience of dreaming about deceased persons of significance to the dreamer would suggest that they lived on and the burials with objects would indicate that some notion of an after life was anticipated. So what do you imagine religion was like before the idea of an afterlife?
I don't know about H.erectus, but I think Neanderthal and Sapiens were religious and believed in an afterlife of some sort relating to the dream world and burial.
I think language and an ego (a self referential abstract model of the human organism/brain)are necessary for religion.
lfen