god as most christians/catholics believe was likely made up long ago when the hunter gathers started to form tribes and they started to talk about where they came from. eventually 'god' became popular and more and more less educated people felt that they had to fit in. societies were smaller and if you weren't with the in crowd, you were out, unless an individual had some sort of influence.
most religions were invented when most people couldn't even read(didn't have the need or desire), so word of mouth made 'god' and most needed some sort of belonging that wasn't too complicated.