There is ample prrof that polytheism can follow monotheism, like many a muslims/christians that started beleiving in various dieties etc.
There is proof of man practicing religion tens of thousands of years before Zoroastrianism - the first monotheistic religion - was introduced.
ZOroaster life is dated around 1000 to 1500 BCE, how can then it be called the first monotheistic religion?
Concept of one all powerful God is present in even the most ancient religions in one way or another, like Hinduism which i think predates Zorastrianism and the Greek who beleived in Zeus the King of all gods.
I didn't say that religion is predisposed, I have been saying that the worship of one God ie the concept of Tawheed (if you are familiar with that term) is already in our heads when we are born, and it is our environment which steers us away from this. This is actually the paraphrased version of a Hadith of Muhammad salAllahualaihiwasallam. The Islamic belief is that all religions initially preached the same message but it were the people who distorted the teachings, so from the Islamic perspective even religion is to some extent preprogrammed. If you read about Arabs in the pre-Islamic period, there were some who used to believe in monotheism and rejected the polytheistic beliefs that existed among the Quraish, and those people were referred to as Hanifa. They had the correct concept of God, but they didn't know how to worship God.
Even if you look at the polytheistic religions, they generally have one main god, and everyone else is a sort of sub-god. From the Islamic perspective the main god is God, and the sub-gods are attributes of the God. And it is the people who at one point starting worshipping the attributes of God and considered those attributes to be a different being.
I thought I had made it clear that my belief was that worshipping of one God is the Fitrah of mankind. If I haven't then, I hope that I have made it clear now.
I believe that mankind could not have created this idea of God, and my intention was to reason that, so that the atheists who believe otherwise would understand.
I think I have already answered this. And if you want a more specific answer then I will start quoting from the Quran and Hadith (if you want me to do that then I will).
I think we are on different pages here. I believe I am talking about belief in God being innate in humans. I think what you said is true as well. The purpose of life, how it began and what should we be doing forward in the life we are given is answered through religion only.
In quest for these answers you will find the notion of God is innate in humans, which is why every religion till date is all about God. All those who professed religion whether they were real Prophets or false Prophets came to the same conclusion i.e. God may it be One or Many but there is a God. Even those who did not believe in the notion of God ironically had themselves called God proving that though they did not believe in the true God still they accept the notion of God.