If you look at animism, on the surface it seems wildly different in various parts of the world, even though the underlying "philosophy" is the same. That is how I imagine separate cultures to arrive simultaneously at the same conclusions.

On the other hand, the core of monotheism (and the underlying non-duality) in all relevant cultures is almost word for word identical, yet the cultures are still quite distinct in their exoteric form in this day and age. That tells me that the cultures must have originated from a common ancestor before they split into their separate cultural branches.

Sure, you may argue that specific entheogen equals specific worldview, but the question then remains why there's no native monotheism/non-duality in east Asia, Americas, or Africa even though Cannabis was present in those regions, too.