How did atheism spred?

Answer 1

Although non-belief dates back thousands of years, it was probably the Age of Enlightenment (in the eighteenth century) that started more widespread scepticism and the beginning of a secular society.

Scientific advances (particularly in geology, astronomy and Biology) in the nineteenth century meant that more and more people - particularly scientists and philosophers were atheist. As education has improved through the twentieth century, Atheism has also grown.

Answer 2

Think of a gentle veil covering the Earth and think of it as what we would now call atheism. As humans evolved they began to use imagination to explain the world around them. Their imaginings evolved into the many thousands of religions we find in the world today. It is religions that spread.

Answer 3

Atheism spreads as people become more educated and have the leisure time to examine the inconsistencies and fallacies contained in religious belief. They then use modern communication to discuss their positions and work towards a more rational world view. They then can adopt this world view without being killed by the theists.