As a DM, I have to park my fantasy ideology on something. I decided that an ancient cult worshipped reptile serpents and raised the thing with a spell that the beast would someday eat one of us and our soul and intellect would manifest in the thing. this began the dragons evolution away from the dinosaur. the dungeon masters detested the cult of the dragon and saw no way stop their need to design winged serpents that can fly by with breath weapon, often negating any defense. pitting species against species with accurate manuals, the dungeon masters decided to cause high levels in sentinet humans by causing dungeons to have features such as the eternal stand off of the giant ant and the kobold, things like this. and then it all made it up to the module we are playing tonight. what have you come up with for the underlying reality behind your D&D thing?