Although there is no doubt that religion has been the tool of the con man (and the tyrant) since the early days of humankind, I doubt that what Mark Twain said is true, or even that he meant it as a serious statement.

It seems far more likely that when Homo sapiens came along somewhere around 100,000 years ago, with his enormous, recently developed brain, he began to pose important questions like: How did all this stuff get here?  What causes day and night and the dozens of other features of our world that are now referred to collectively as astronomy?  Why do bad things happen to good people, and vice-versa?  What causes illness?  What happens to us after we die?

The idea of an all-powerful God, or perhaps a number of them, seemed at the time to be the best possible explanation.  But about 2500 years ago there arose a stirring in our species that perhaps we might begin to figure this stuff out by studying it and applying reason to it.

Aristotle told his pupils to design and use experiments, and the scientific method was born.  Ever since, we’ve been chipping away at the vastness of our ignorance of natural phenomena.

The Origin of Religion