Ah, but have you seen The Conqueror? Where he plays Genghis MFin' Khan?!?!?

My wife's theory, which I think is pretty good, is firewood. Burning logs get that look of glowing scales in the heart of the fire. Humanity, no matter where you're from, grew up gathered around open fires... considering nearly every culture dreamed up dragons of one sort or another the genesis would have to be something universal.