This seems also to go along with the development of man. I was watching a documentary on TV weeks ago which stated that one of the missing links in mans pregression from ape was by eating the brains of animals killed originally by other animals.
We had developed the capability, at that time, to figure out how to extract the brains, which are high in fat and protein. This developed our brains even further and promoted our growth, not only physically but mentally also.
Interestingly the archeologists can also find evidence of other developing human beings who were bigger than the strain we evolved from. These appeared more physically developed brain cavity was smaller and they were still very ape like in statue and vegetarian. According to this program, this line of developing human died out.