The concept of atheism is entirely dependent on the concept of a God. If the concept of God had not arisen, there would be no atheists.
While atheists of one sort or another have, no doubt, existed since the dawn of humanity, it is significant to note that purpose, meaning, and morality have always been closely tied to religion – even those religions, such as Buddhism, that don’t admit to a personal God.
Divorced from the concept of God and the practice of religion; a vacuum occurs, within which purpose, intelligence, and morality must find some other meaningful grounds. –