There have ALWAYS been atheists.
That is why they, more than any other group, are condemned in every holy text there is.
There were Arabs laughing at Mohammad’s fanciful notions, there were ancient Hebrews that are vituperated in the Bible, and so on.
“The fool has said in his heart, ‘There is no God.’” Psalm 14:1 - if written by David, about 3000 years old. Appears that you are right - there have always been atheists.