I have heard so many times from atheists, agnostics, etc.. that religion is a natural part of human evolution and we will evolve out of thinking there is a God or dogma. Why? There is no way to prove that statement.
The statement doesn't need proving.
It's a speculation based on extrapolating evidence from the past into the future. Before the first wave of scientists, the ones such as Copernicus, Kepler, Galileo, Newton, Vesalius, Harvey, Bernoulli, Dalton, Avogadro, Priestly, Boyle, Coulomb, Lavoisier, Volta, etc., the workings of the world were explained as Apollo pulling the sun through the sky, Thor fashioning and throwing lightning and thunder from the heavens, various sprites and pixies animating the rivers and the wind, etc..
But because of these early scientists, our view of the universe evolved into that of a giant clockwork running on autopilot according to assorted rules and laws. No god was needed to account for the day to day motions of reality. Currents flowed through wires not because angels pushed it, but because of the nature of matter. The ruler god was no longer needed, but a creator god was still necessary to account for how the clockwork came to be. And thus, deism was born. A god built our world to run unsupervised, and then left it.
Next came a second wave of scientists like Hubble, the cosmologists, and Darwin, who explained how our universe could assemble itself from a hot, dense ball without intervention, and how an ancestral population of cells could generate the tree of life and the remains of the extinct forms we encounter. With this, the builder god disappeared as well. All that remained (and still remains) the origins problems - where did that primordial tiny universe come from, and where did that first population of replicators that evolved come from?
As the gaps for this god narrowed, it became apparent to many that there may be no need for any god hypothesis at all to explain any of this. We have naturalistic hypotheses for the origins problems - the multiverse and undirected, naturalistic abiogenesis.
From this comes the rise of atheism. In the United States, we have been tracking the steady rise of the "nones" and concomitant decline of those self-identifying with any god or religion. Within religion, there is a trend toward more Eastern theistic concepts, pantheism, New Ageism, assorted pagan and Wiccan "isms" - each also a step in the direction away from the anthropogenic god concept of Abrahamic monotheism - the all-powerful creator and ruler god..
Even the Abrahamics are softening under the influence of the progress of science. Christians are accepting evolution, rewriting their hell theology, and calling much of their scripture metaphor and allegory. Jews are rarely religious. Most I know are atheists.
All of these trends point in the same direction: the decline of religion in general as the march of science and understanding proceeds
It's pretty easy to extrapolate forward to a time of little or no religion, and to suggest that religion represents the phase in man's cultural evolution where he went from first being able to wonder and ask about where it all came from, to the time that he had his answers, answers which don't include gods.
We don't expect religion to disappear altogether, but to follow the path of say Druidism or Zeusism - once dominant worldviews in other times and places, but now hardly a blip on the radar. Many people don't realize that these traditions aren't extinct, that's how uninfluetial they are. That's what I see being the fate of religion in the West. The Eastern philosophies may remain influential longer, but most don't really resemble religion as I am accustomed to it here in the West in the first place. They seem pretty much like my own humanist worldview with a universal spirit of some sort added.
How could God just have been thought up if He wasn't real?
That's a remarkable question. How was Harry Potter thought up if he wasn't real?
One of the worst arguments for the existence of God is Anselm's ontological argument, which basically says that "if God is a being than which none greater can be conceived, then God cannot not-exist, or else we could conceive of a greater being-one that exists."
What?