Never.

The reason is simple, and it is cultural evolution, control theory and meme theory. Religion is an immensely important memeplex for society which contributes societal survival. It cannot be substituted with anything else.

CAUTION: This is now an INTJ speaking! You may find the following stuff extremely disturbing!

It all boils to the fact that human beings are biological creatures and the biological evolution states the question is not about who is right but who is left. Those people who produce the greatest number of surviving offspring propagate their genes to the future generations. Those who do not breed, go extinct.

The observation is that religiosity is the strongest indicator of fecundity. The most religious people produce the greatest number of offspring. They produce them regardless of what their social standing or living standards are. This was first observed in Israel. Israel was founded by secularist Jews, most of which them were Atheist and Socialist. Jews of all standings moved there, also including extreme ultra-Orthodox Haredis, who are religious to the boot. When David ben-Gurion was asked what to do with the Haredis, he said “Time will deal with them”. Didn’t happen. The Haredis breed, and they breed a lot, and in seventy years they have pretty much outbred the secular Jews, and have become an influential menace in Israel. The result is that Israel is on its way on turning yet another religious “-stan” state as its neighbors.

TL;DR: Religious people breed. Atheists do not breed. The future does not belong to the brightest, but to the frummest.

Moreover, on Donella Meadows’ control theorem of 12 point of leverage, religion is the most fundamental. Religion represents the very mindset where paradigms spring, the power to transcend the paradigms, the leverage point #1. Transcending paradigms may go beyond challenging fundamental assumptions, into the realm of changing the values and priorities that lead to the assumptions, and being able to choose among value sets at will.

This is the reason why KGB and Soviet Union considered spreading Atheism and anti-religioius work so important. As long as the Western world had sound religious and spiritual basis, it was immune to Communist subversion. Conversely, the people most eager to adopt Communism and Communist agenda were Atheists. Destruction of religion was an essential step on getting the Western societies to prone to collapse and conquest. This is something the Westerners never understood - and never will.

Religion is the very basis where societies are founded. Marx was wrong. The society does not create a religion. Weber was right. Religion creates a society. Each religion creates a society of its own image. Every Lutheran society is a Sweden. Every Calvinist society is a Switzerland. Every Anglican society is an UK. Every Catholic society is an Italy. Every Orthodox society is a Greece. Every Shia society is an Iran. Every Sunni society is a Turkey. Every Wahhabi society is a Saudi-Arabia. Every Hindu society is an India. Every Jewish society is an Israel. And so on. Religion dictates the very set of values, the very concept of right and wrong, valuable and worthless, approvable and disapprovable, good and evil, the way to relate to the society, government and outsiders and to each other. There never has been a religionless society and never will. It will collapse.

TL;DR; Society does not create a religion. Religion creates a society.

And this all is due to meme theory. Meme theory is the same foundation for the cultural evolution as gene theory is to biological evolution. Those two are really analogous - the only difference is that the cultural evolution is Lamarckist and biological evolution Darwinist by its nature.

Memes are the information carrier units in the cultural evolution like genes are in the biological. Together they form meme systems, memeplexes (analogous to organisms). And the very same concepts of ecology, struggle of existence, survival of the fittest, ecosystems and ecological niches apply. And religion is a memeplex par excellence. Religion exists because there is an ecological niche and function for religion, which nothing else than a religion can occupy.

Religions are not “viruses of mind”, like Richard Dawkins suggested, but they are fundamental memeplexes, as Susan Blackmore has suggested.

Religions are there because there is an ecological niche. Like in biological evolution, you can exterminate the occupants of an ecological niche, but it sure will get re-occupied. An empty ecological niche is an unnatural state.

Atheism represents an empty ecological niche.

And an ecological niche which is vacated is sure to get occupied. In a case of a religion, if not by a sensible religion, then by one which is completely nuts.

Remember when I said the question is not about who is right but who is left? This applies verbatim to cultural evolution. The question is not of which meme or memeplex is materially correct, but which can propagate itself most vigorously. This is the reason why I studied astrology as a teen: to make me more popular among other girls. I knew since beginning it was all Bravo Sierra, but I also knew it was me a way to enhance my status on the pecking order. Studying astronomy was a social disaster among other girls - it was ‘nerd’ stuff and very uncool.

And this also means Atheism is a social suicide. Atheism means difficulties on finding a spouse, and if Atheists marry, they do not breed. Atheists tend to have few children, 1 or 2 perhaps, and many are voluntarily childless.Religious people breed. My mom said my brother: “Rather get yourself a wife of faith than a faithless one”.

And religions do not propagate by conversion, but by breeding.

And no, it is not about prohibiting abortion or contraception. It is that religious women themselves want large families. Every child is a gift of God. My sister-in-law has six kids: she said she wanted a large family and when there are enough of them, they take care of themselves. [Let’s say her own name means “gift of Lord” in certain language.]

This is the same in all religions - not Christianity only. Religiosity and fecundity go hand in hand. Which means the Viljanen genes are very likely to survive in the biological evolution and struggle of existence, unless a genocide occurs.

This is also the reason why Europe is facing a societal disaster. Atheism is nothing new in history, and it is tightly linked with anacyclosis. Atheism is a phenomenon which emerges at the last stage of anacyclosis, before the societal collapse or upheaval; it means the society has turned from democracy into ochlocracy. It means people, having lost faith in the supernatural, have lost the faith in the future - and on themselves. “For behold, the days are coming in which they will say, 'Blessed are the barren, and the wombs that never did bear, and breasts that never nursed.” It all has occurred already so many times before. Every time a society which has lost is religion, has also lost its faith on itself , birthrates declined and collapsed - and the result has been a societal collapse.

And each time, the result has been re-emergence of religion. Not necessarily the same as before the collapse.

Europe is heading to demographic catastrophe and collapse. It will be seen which religion will emerge as the victor and which will occupy the empty memetic ecological niche. I wish it will happen only when I’m dead and I won’t be seeing it, and I wish it will not be Islam.

Can science occupy the same ecological niche? No. Religion and science belong in different domains in cultural evolution - and they have different ecological niches. This is something the Atheists never realize - and never will. They keep propagating the gospel of science - with notoriously poor results. Conversely, each time science has been attempted to fill that ecological niche, the result has been a disaster - as in the Nazi Germany and Soviet Union. Holocaust would not have been possible without scientific Weltanscahuung.

Why there has never been a religionless society? Why there never will be? The reason is that the religion memeplex is not about being right. It is about being left. Religion is not for individuals; it is for societies. Religion is the mortar which binds the individual human bricks of the society into a stout brick wall. Remove it, and all you have is a heap of bricks which will collapse at slightest push. This is the reason why all non-religious ideal societies have collapsed at third generation latest - and why religious ideal societies can last for millennia. Monte Cassino monastery had been founded 529 AD, and Heian 711.

And this is the reason why religion is there and always will remain there.

TL;DR; Religions are memeplexes and there are ecological niches for them. Religions are for societies, not for individuals.