Chasing His Tail

Dogs are too funny! Buddy chases his tail all the time and never has caught it, not even once, after four years. He always goes around in little circles, always ends up almost falling over, growling at his own tail like it will stop and wait for him to catch it. Then there is Duncan who has no tail, so what does he do? He chases Buddy's tail! I always wonder what is it that makes a dog chase his tail or what makes a dog chase another dogs tail? I can get them toys and play with them for hours but they must eventually get bored or annoyed because they always revert back to tail chasing. Why do they chase their tail in the first place? If a dog ends up chasing and catching his own tail, what will happen? Will he hurt himself? If he bites his own tail, will he stop chasing it? Do dogs eventually outgrow chasing their tail? Even if I never figure all of this out, it's great entertainment just sitting and watching all the chaos!