It is interesting to note how various spiritual teachings developed throughout the world. It would seem that nearly every ancient culture started off as "animist" (i.e.: everything having an associated "spirit"). These were sometimes personified as "gods" and "goddesses", symbolized by animals, or some other recognizably "living" thing. Historically speaking, there is a general tendency of people moving from polytheistic "tangible" dieties, to a progressively more "abstract" monotheistic diety. On the one hand, these developments might have been accompanied by actual physiological changes that helped people to perceive reality in entirely new ways (e.g.: Julian Jaynes' Bicameral Mind concept).
On the other hand, spiritual teachings often act as a form of social cohesion, so this change seems to correspond to the move from smaller tribes to larger nation-states. This is still apparent even within the most well-known religions. For example, what many people call "Hinduism" in the west, is not a single religion but actually a collection of spiritual teachings from many different tribes. The various forms of Buddhism were a way of systematizing all of those teachings by either completely removing or replacing all of the polytheistic components of it.
Similarly, the spiritual teachings of ancient Greece started off as polytheistic (e.g.: what we normally view as Greek "mythology") with their associated local rituals (e.g.: the "Eleusinian Mysteries"). These were later united by the Pythagoreans into a single system through their doctrine of "Emanationism" (i.e.: all the seemingly separate gods and goddesses were considered aspects of The One, a genderless abstract diety that transcended them all). Many spiritual teachings have followed this type of trajectory and we could point out several more examples (e.g.: ancient Egypt, Persia, etc.).
This connection between physiology, perception, and social structure, especially as it relates to the development of spiritual teachings, does not seem to be well studied. However, it has deep relevance to life now. The "Abrahamic religions" (i.e.: mainly Judaism, Christianity, and Islam) are literally the most predominant social forces in the world, but a peek into their history shows that the intentions behind them were very different from what they are now.
For example, as strange as it might sound, I believe that the original intention of Christianity was "anarcho-communism". The early Christians were Jewish "anarchists" in the literal sense of the term (i.e.: the prefix "an-" + the root "archos" = "no rulers"). They did not accept any human-run kingdoms as legitimate as per the instructions in 1 Samuel 8 of the Old Testament. But they also did not believe in "lawlessness" (in the sense of "might over right"). All laws were to be based in ethics, of personal striving towards virtuous thought and moral behavior as a sincere expression of love towards others.
In order to survive independently of the kingdoms around them, they were "communist" in the sense of "no classes" (i.e.: they made self-sustaining communities where there was no hierarchical structure and where nearly all property was held in common). Nowadays this is referred to as "cenobitic monasticism". Both the Buddhists and Pythagoreans had done similar things before them, and there are many instances where their teachings and practices overlapped (e.g.: the Therapeutae sect of Alexandria). There are others.
...It is probably needless to say that nearly all of these groups were persecuted and their teachings twisted by various despotic rulers in order to keep people as slaves. People sometimes practice with little understanding of the history, meaning, or purpose behind their rituals and metaphors.