What came first, the atheist or the theist?

[Tiberius]

in order for me to not believe in the fadgdvaet, i need to first know the concept of the fadgdvaet to deny it. before you mentioned it, i neither believed nor didn't believe in it.

You talk about "not believing" and "denying" like they are the same thing. They are not. Not believing in X is when you have no belief in X. Denying X is when you state categorically that X is not true. Yes, to deny something you need to know the concept, but the same is not true if you don't believe in something. There are no requirements for not believing in something, other than not having a belief in that something.

Your final statement (I neither believed nor didn't believe in it) is a violation of the third law of logic, the law of excluded middle. For any proposition, it is either true or not true. So yes, I'm afraid that either you did believe or did not believe.

the definition of an atheist is someone who doesn't believe in god. so before this concept arose we first needed the concept of believing in god in order to deny it.

before the concept of god was created, humans were not non believers in god, because they had no idea what it was that they weren't believing in. wow, that's one hell of a sentence right there!

You are confusing the actual belief (or non-belief in this case) with a description of the belief / non-belief. Yes, in order to talk about a belief or disbelief, the concept must be known and understood. However, this requirement is non-existent in order to have a non-belief, since anything that is not a belief is a non-belief.

would you say that all monkeys and other animals are atheists too? nonsense. they have no concept one way or the other, neither would humans have.

By the definition of atheism, they are, or at least they appear to be since science tells us they have no advanced thought on the level that we do. You do not need to have know the concept in order to not believe in it. Here's an often used analogy for you:

Does one have to know about the concept of stamp-collecting in order to not collect stamps? The answer is no. Amazonian tribes that have no contact with the outside world and don't have any concept of a "stamp" are categorically not stamp collectors. People who don't have any concept of a God are categorically not believers.

definition of an atheist: someone who denies the existence of god.

before the concept of god was created, people were not denying that he existed, so there were no atheists until the first theist arrived.

That is the definition of a strong atheist, not an atheist in general. Ask all the atheists here if they agree with that definition, and I guarantee that 90% of them will say no. Atheism is the non-belief in the existence of Gods. As long as you don't believe in God, you are an atheist.

Before the concept of God was created, nobody believed in God. Hence, everyone was an atheist.