The Source.

When the council of dragons learnt of the approaching comet, they gathered together and birthed an egg. In the heat of the comet's impact, and amidst the death and destruction of its progenitors the egg incubated. And a millenia later, tetris the one true god, emerged from within into a barren world.

Before the comet fell, dinosaurs birthed an egg.It all began when the comet fell. Or at least once the elders cam to know knthe comet would fall.