The Dragon Time

From about 12000 years ago to about 5000 years ago was the period of history known as The Dragon Time. During this period of time, dragons were much more populous and much more active in the affairs of species they consider lesser (which is to say, all of them.) Dragons of that era became warlords, emperors, and conquerers, and other dragons who took pity on the lesser species rose up to become leaders of cities and nations themselves in order to protect and fight the threat of the more aggressive dragons. It was a time of chaos and strife, for even under the protection of a dragon, other dragons would still wage war.
Many dragons died out during this period, usually at the hands (claws?) of other dragons contesting their lands and hoards. Numbers dwindled throughout, and the dragons who remained became more and more disillusioned. No longer did it seem worth the effort or risk to take so much at once by force, and so gradually, they retreated to more private lives.
The end of the era is traditionally marked with the foundation of Androcas, a nation of humans, for humans, by humans, as the first King Androcas cast of the chains of the dragons and declared himself independent. This is noted as Year 0 in the currently most-popular date system, the Androcian Calendar.