Which was first: Atheism or Religion?

[Brian37]

If atheism was first, then religion was created by atheists.

Can't really put it like this, our evolution had prior forms of sapiens and we also did not evolve to "fact find" as our primary goal. Our species evolved to seek patterns, our flaw is that we tend to gap fill more than fact find.

There were many skeptics even prior to human written language, if there had not been questioners, our species never would have evolved, but it is not a "chicken vs egg" deal here. Our species evolution has always depended on multiple factors.

The only thing you can say is that religion is a result of our flawed perceptions, but that is not the result of one individual doing that.