Stone tools permitted a greater shift to a carnivorous diet because the ability to cut meat into small pieces reduced the amount of chewing required to extract nourishment. Less chewing reduced the need for large, powerful jaws. The advent of agriculture accelerated this trend.

Corruccini reasoned that tooth size is preprogrammed to fit a jaw subjected during growth to levels of mechanical stress in line with a natural childhood diet. Subsequently, when the jaw does not get the needed stimulation during development, the teeth become crowded at the front end and impacted in the rear.