The term ‘atheism’ originated in France back in the 16th Century. However, ideas that make up the base of atheism can be seen from as far behind as the classical antiquity period.
Atheistic schools of thought can be found in Indian subcontinents history with beliefs that there is no God. In fact, the human being himself is powerful enough to determine the course of their life, action himself to create necessary changes that would allow him to become successful in life. This materialistic approach to life originated in India back in the 6th century but is not part of the six orthodox schools of Hinduism today.
The Enlightenment Era is generally credited as the time when atheism emerged in the western world but when you look in deeper you see roots of the concept in pre-Socratic Greek Philosophy times. They viewed religion and belief in accountability to a God as a man-made invention meant to keep human beings on the morality track. It is from these times that scholars such as Socrates became public with what was considered atheistic beliefs and resulted in him being sentenced to death. Another thought process that emerged during this era was that the ‘gods’ were past’s heroes, conquerors, etc that had cult fan following which transformed into religious devotion over time. Many atheists also thought that even if there were gods, these supernatural beings were actually unconcerned with humanity and hence, all the trouble in the human world exists. Over the course of the classical antiquity, the precise meaning of atheist changed.
Europe was relatively atheism free in the Middle Ages with focus on religion, theology and metaphysics. However, different views emerged in terms of nature, transcendence and knowledge of God. Come the time for Renaissance and we saw expansion in the ideas of freethought and allowing religious skepticism. This is the time that the Christian Church faced a lot of opposition from individuals like Leonardo Da Vinci, Niccolo Machiavelli, etc who all were deemed atheists, illuminati, etc for their forward thinking.
In recent times, the atheism lifestyle has flourished in many societies in terms of Marxism, feminism, anarchism, secular humanism and the science based rationalistic movement. This time also saw an increase in religious freedom for minority religions. Communism and states like the Soviet Union actually propagated state atheism, sometimes even with violent measures.
Atheists today are more knowledgeable about the religions of the world than an actual follower of the belief. A 2010 survey in U.S.A revealed that non-believers scored better on religious questions than actual Christians and Protestants. One can only suppose they want to be better prepared with religious knowledge to defend their own non-faith.