I'm one of those kind of people that loves science and knowing the scientific reason behind things, so the answers; just because, and that's the way that God intended it aren't good enough reasons for me. Sure they are good reasons but things like; Why does the tail of a cat wiggle when its excited to see you? (I sort of already know why they purr as it's sort of like a Yoga meditative state) or why do dogs' tails wag or seem like they know just when exactly you are going to come home? Why do we smile, laugh and cry and why can't other animals do the same? (Other primates can smile but not for the same reason) Finally, when somebody feels sick why is it that everybody else start feeling the same way?