Animals seem to manifest tendencies seen in human beings. And, apart from the Darwinian theory, from a spiritual perspective we can say that it's not a coincidence. Researches on reincarnation conducted for over 40 years by Ian Stevenson, Chairman of the Department of Psychiatry at the University of Virginia, on nearly 2500 children who reported past life memories, validated the possibility of reincarnation between human beings of different cultural backgrounds but also between humans and animals. Focusing on further hypothesis based on these findings, this book intends to stimulate the reader into thinking about how the instincts of the physical world affect our conscience as human beings. Based on many travelings around the world, and the combination of these experiences with knowledge in spiritual evolution, it was easy to see the correlation between reincarnation and the attitudes observed in animals and humans, just like Darwin saw it, even though in his case while focusing on the physical aspect of it instead of the spiritual. At some point, it's likely that everyone on earth has spiritually occupied the body of an animal, and the characteristics of such evidence may prevail, especially if there isn't any responsibility for our human existence as a conscious and creative being. Joseph "Yellow Kid" Weil, one of the most famous con men in history, said: "The desire to get something for nothing has been very costly to many people who have dealt with me and with other con men, but I have found that this is the way it works. The average person, in my estimation, is ninety-nine per cent animal and one per cent human. The ninety-nine per cent that is animal causes very little trouble. But the one per cent that is human causes all our woes. When people learn -- as I doubt they will -- that they can't get something for nothing, crime will diminish and we shall live in greater harmony". The prevalence of instinctual behavior in so many people leads us to consider different types of bestial manifestations and tendencies. It's interesting to notice that some individuals enjoy the sunshine and activities related to sharing love, like dogs, while others are very independent and emotional, like cats, but we also have a big proportion of individuals that, like monkeys, only care about immediate gaining, even if they have to take it from others, and their whole life is based on that. It's also quite interesting to notice how affiliated we may feel to animals that share similar traits to our own character, and how much most people prefer to be led by their instincts rather than their conscience. With these insights in mind, this topic will be further analyzed taking into consideration its implications and relevancy as a spiritual teaching.