The overall field is called allometry. Kleiber's Law is another reason behind our size and shapes: http://en.wikipedia.org/wiki/Kleiber%27s_law http://en.wikipe

The overall field is called allometry. Kleiber's Law is another reason behind our size and shapes: http://en.wikipedia.org/wiki/Kleiber%27s_law http://en.wikipedia.org/wiki/Kleiber%27s_law "for the vast majority of animals, an animal's metabolic rate scales to the ¾ power of the animal's mass."