An ancient ancestor of ours who had rudimentary logic skills coupled with little information about his surrounding environment. He came up with the best explanation for the nature of the universe as he knew it that could have been expected of him. These days, we have more data, and logically our explanation should change to fit that data.

God

i believe it was the nerd of the stone age. he saw the big bad hunter/chief and how he got all the things he wanted by scaring everyone through physical prowess in to giving it to him. So he thought i can scare people too but he chose invisible forces that no one understood. It worked out he got to sacrafice "virgins" and got them to give him money. In the end he became more powerful then the chief because the unknown is scarier then the known.

Men who wanted to control other men/women and what better way than using fear and brainwashing

Define "religion". The human species is evidently naturally religious and superstitious; primitive (and even modern) men naturally go through life in certain repetitious rituals to which they attach some transcendant significance and value (and sometimes magical effect), and that they at some level of their consciousness feel that "the whole world will come to an end" (or at least the world they know and love) if the rituals are neglected or - worse - desecrated. Just consider ongoing reactions to flag-burning and you'll see we're not so far removed. We build deep sentimental attachments (or aversions) to symbols and symbolic acts - some more than others - and different ones for different cultures and sub-cultures (a gun MEANS one thing to an urbane liberal professional living in Seattle, and it MEANS something completely different to a 6th generation mill worker in the hills of western Pennsylvania). Also, we at some level naturally believe that the universe and all that is in it is alive - just as a child knows his Teddy bear is real and alive, that it loves and cares and has feelings that can be hurt. We also are naturally a story-telling, pattern-making species - NOT a logical one. (Our "reason" evolved not to find the truth but to play social games.) We have a natural bent/susceptability for sympathetic magic, omens, and divination. On the whole, people believe things not because of logic or evidence but on the basis of 3 sometimes conflicting, sometimes reinforcing factors: (1) how tantalizing the story is/how well it's told; (2) how well it fits with our inculturated plausibility structure; and (3) social group identification. Fact is, modern, urbane, educated, "enlightened" men don't have fewer superstitions and taboos than primitive anamists: they just have different ones. Finally, we naturally assume that there is some order to the universe and even purpose for it. Even those who have come to reject the latter intellectually none-the-less routinely act on the basis of that assumption.