I loved the way Douglas Adams thinks religion came about

Basically, mankind evolved into using tools and everything he therefore makes also has a purpose.
So then he starts to think what the purpose is of caves and rivers and trees and mammoths (mammoths are great! you can make clothes out of its fur, you can eat its meat and you can use its tusks to make weapons to kill other mammoths!).
"Well, they seem to make my life much easier, so they must've been made for me! But who made them? Must be someone who looks like me, because we're the only kind that makes tools. He has to be bigger, because he can make really big things that I can't. And he has to be invisible, because I can't see him."
It all started from the misconception that something has to have been "made".