A friend found a tooth.

This tooth mated to another molar creating a grinding surface.

Occluded molars resulted in increased caloric extraction and this energy surplus then permitted increased physiologic complexity resulting in the development of mammalian species including hominids.

The hominids took this a step further through the domestication of fire. This again resulted in increased caloric extraction. This energy surplus permitted increased physiologic complexity notably in the creation of cognitive tools that permitted the greater exploitation of external resources.

Chief among these external resources was the exploitation of fossil fuels (frozen sunlight) which permitted increased caloric consumption and led directly to the recent phantasmagoria we call modern civilization.