Imagine a world in which there are dinosaurs, monkeys, guerillas, alligators, and all sorts of animals, a world that you are aware of but not part of, yet, you find the world to be so fascinating that you desire to visit it, but you have no physical form to do so, because you are spirit, and because you are spirit you are free to incarnate into physical forms and to thereby experience physical life, its limits, its fascinations, its dilemmas, and so on and so forth.
Tempted, you go aheadand incarnate, and at first, incarnating into physical form is something that is done as a mere sideshow, because you are consciously aware that you are spirit, but as you incarnate from this animal to that animal, from this thing to that thing, you begin to lose sight of who and what you really are, which is spirit, and more and more begin to find yourself becoming to believe that you really are exclusively that physical thing, subject to physical laws, subject to the lusts and needs of a physical body, subject to all the limitations of material life, but in a perverse way, enjoying the thrill of that experience, the power of being able to take from other animals, the excitement, the everyday drama, and the thrill of physical form.
Yet, on the downside, your physical body suffers harm and damage, it ages, it experiences cold and heat, hunger and satiation, victory and defeat. In addition, whereas once you were free to disincarnate from one animal to another, now, your spirit is somehow encased within the physical, and for the most part, forgotten, so that, whereupon the death of that physical form, there is a momentary confusion, as to who and what you really are, before the scales fell off of your eyes, and you know that you are as you always had been, spirit, but your spirit, itself, feels unclean, and unworthy to join itself back with the First Cause, for having lived a life as an animal, you had taken on the characteristics of an animal, of selfishness and of aggression, which are inimical to the attributes of spirit.
This meant, that you felt a need to correct what had gone wrong, thereby having a strong desire to re-incarnate back into animal form, not to continue along the path that you had been on, of pure animal passion, but to take the animal, and to evolve it into something that it had not previously been, so as to make that animal, not only more sentient, knowing right from wrong, but to make the animal more sociable, less selfish, and more in harmony with the First Cause.
Unfortunately, while there were those in spirit form that felt the urge to reform and to uplift the animals that they had incarnated into, there were many others, that felt no need to do so, whatsoever, so enraptured in physical life that they had become, that they preferred not to change a thing, to ignore that still, small voice, and to do the things that gave them pleasure, or power, or satisfied their material lusts and desires, so that, this material world, once a fascinating paradise, became instead a battleground, of which this battleground continues until this very day, good v. evil, right v. wrong, selfishness v. unselfishness, on and on, but the end result will be to come back to how it was, in the beginning.