There is an instinctive knowledge that there are other levels of existance- a knowledge first attained when we began to evolve the concept of spirit, and realized that we are ensouled beings.
At first, and still largely to this day- this understanding was visualized as a phenomenon akin to Russian dolls- the soul lives inside us, a diaphenous essense that flees with death, and carries our awareness with it.
As humankind began to develop their understanding of this concept, they began to think of it as being projected from a higher realm, into the physical, where it lives inside the housing of flesh that is the body.
Many civilizations respected this housing for the spirit as the "temple" in which the life essense- a gift from the divine- was contained- a precious and mysterious fluid that must not be spilled, misused or wasted in any way (an irony during millenia of human existence when life was cheap, and often spent for entertainment). In such cultures, life-force was often associated with the liquid portions of our physicality, such as the blood, the semen, the tears of physical beings.