Were people atheists before the concept of God was developed? (If you’re a believer you may prefer the question: Were people atheists before the existence of God was revealed to humanity?)
It depends on how you define that letter a that’s the prefix in the word atheism.
You may define the a as meaning: not; without; lacking the quality of. As in the way that asymmetrical means not symmetrical and amoral means without morals.
If you define it that way, then, yes, before the concept of God entered our awareness everyone was an atheist. Because they simply weren’t theists.
However, if that letter a is given a stronger, more active definition, things are different.
In the stronger definition of the term, an atheist is a person who is in active opposition to theism, rather than simply not being a theist. More like being an anti-theist.
According to this strong, active definition of atheism, you can’t be an atheist until there’s such a thing as theism. This is because you can’t take a stance against something – or be anti something – unless that something exists. You couldn’t, for instance, be an antivivisectionist before there was such a thing as vivisection, or be an anti-abortionist before there was such a thing as abortion.
Similarly, you couldn’t have anti-aircraft guns before there were aircraft.
There’ll be more on these different definitions of the word – non-theism and anti-theism – later.