What is the history of elemental bending?

Answer 1

With the exception of water bending, bending was learned from animals. Fire-bending was learned from watching Dragons. Air-bending was learned from watching Flying Bison. Earth-bending has the longest story. Two lovers (in what would later be called Omashu) from battling countries learned Earth-bending from Badger Moles so that they could be together. They made a cave under a mountain that is lit with crystals when dark so they could find each other and be left at peace. Water-bending was learned from watching the Moon bend waves in the ocean. A fifth bending also exists (*spoiler*) which is bending-bending (or spirit-bending) and is known only by Aang and Lion Turtles. Aang having learned it from a Lion Turtle. I do not know why everyone (except the Avatar) can only bend their native element. Or why only some people are benders. I do know that ALL air nomads were air benders. It SEEMS as though anyone should be able to learn to bend any element, but it does not work that way. Though the implication seems to be that bending has a genetic component, rather than a national one (especially since Air nomads are so spread-out).