Explaining a full history of dragons would take too much time, and too many words. Therefore, I will provide a brief and (hopefully) helpful history of dragons.
Dragons have been around since the beginning of time. Their original birth or creation is unknown, though some legends call them primordial beasts- nearly gods. And so it would seem, to those who have seen a dragon in its full glory. Few things can match the splendor of a dragon in flight.
The first dragons were wild and savage beasts. They roamed the earth as an unstoppable predator, carried aloft on massive wings. They had no breath weapons then, and no magical properties. They were little more than winged lizards. However, at some point in their exploring, dragons found a deep and ancient source of magic. The dragons that visited this source came away changed. They were intelligent, and gifted with strange talents. The breath weapons were one of these gifts. The weapon reflected the personality of the dragon, and their scales changed as well, shimmering in iridescent colors, rather than drab browns.
The dragons lived in power, until humans came along. This was known as the Age of Glory- an age where dragons ruled the earth. The humans then were little more than toys to the dragons, and they enslaved them, and stole from them whenever they chose to. However, this was also an age of death, for dragons killed one another for dominion. And so it continued, until a gold dragon by the name of Avana Goldscales gave humans the gift of knowledge, allowing them to fight off the dragons, and defend themselves. Avana was later executed for treason. However, her death and her life's work helped the dragons to construct a new ruling system.
Instead of fighting one another, dragons joined together in a single community, ruled by a council of 12. On the council were six metallic dragons, and six chromatic dragons, to have equal representation of both types of dragons.
For the next several centuries, dragons interacted often with humans. In each generation, the dragons would bless one individual, who would be given dragonlike strength and abilities. This human became known as The Dragon Hero, and could be anyone at all, from the greatest lord, to the weakest peasant. The Dragon Riders were also formed, as a way of keeping peace between the dragons and the humans.
Next, however, came the age of the slayers. Humans, seeking to gain glory and power, sought and killed dragons. The dragons responded in fury, laying waste to cities as punishment for the slayers actions. A common saying lives to this day: 'Those that slay dragons do not die quietly'. In a rage, the dragons withdrew all contact with humans, and so hid themselves away for countless centuries.
After this came the reforming of the riders. Some humans and dragons, braver than most, sought each other out, and bonded, hoping to reform the lost riders, and therefore resume the peace. They were permitted, and gradually became messengers between the dragons and the human world. However, the Dragon Heroes were no longer, for the dragons blessed no more humans. The riders continued, and continue to this day to keep a quiet peace between the two races.
And so concludes the brief history.