Every creature that came before us in our evolutionary chain (and this is true of all sentient creatures we see around us), as a species, its individual members wanted to SURVIVE. I consider this idea to be self-evident. If that were not the case, none of us would be here.
What do all major religions have in common? Two things:
1) Some sort of promise for adherents wherein they effectively never die. The individual, will in some sense, continue to exist, in perpetuity, even after their physical body dies.
2) Some implied protective structure for adherents via supernatural order, beings, or metaphysical law (karma and such). If you follow this belief system, you will be some sense protected from the vagaries of the universe, the things that may try to harm or kill you.
So my theory is that once intelligence evolved to the point where a creature could imagine/conceive of a mechanism by which they are magically protected from harm/danger/misfortune, and by which they could LIVE FOREVER, they constructed such mechanisms for themselves. Then they join together (pack mentality) to convince one another that these ideas are true. The more we perceive that others around us believe a thing, the easier it is for us to also believe in said thing.
Religions have tremendous allure to a great many people because all species arise from previous consecutive ancestors, all of whom had a will (and the means) to SURVIVE.
You take away the "magical protection while alive", and the "eternal life after death" parts of religion, and you will have no adherents. Religions all appeal to our most basic instincts.
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