On the level of the body, humans are very close to animals. All the basic bodily functions, pleasure, pain, breathing, eating, drinking, defecating, sleeping, the drive to find a mate and procreate, and of course birth and death, we share with the animals. A long time after their fall from a state of grace and oneness into illusion, humans suddenly woke up in what seemed to be animal body, and they found this very disturbing. “Don’t fool yourself. You are no more than an animal.” This seemed to be the truth that was staring them in the face. But it was too disturbing a truth to tolerate. Adam and Eve saw that they were naked, and they become afraid. Unconscious denial of their animal nature set in very quickly. The threat that they might be taken over by powerful instinctual prices and revert back to complete unconsciousness was indeed a very real one. Shame and taboos appeared around certain parts of the body and bodily functions, especially sexuality. The light of their consciousness was not yet strong enough to make friends with their animal nature, to allow it to be and even enjoy that aspect of themselves, let alone to go deeply into it to find the divine hidden within it, the reality within the illusion.
So they did what they had to do. They began to dissociate from their body. They now saw themselves as having a body, rather than just being it.
Reference : The Power of Now. Eckhart Tolle.