The most impressive feature of human evolution is the development of an amazing brain. The effort to develop such an ‘exaggerated’ organ was possible thanks also to limitations imposed on the development of other organs. If one makes an enormous mental effort together with a great physical one, the resulting efficiency of the two efforts is less than the sum of when performed separately. However, the reduced physical efficiency is proportionately greater than the reduction of the mental efficiency. Therefore, when necessary, the brain although accepting some restrictions, manages to impose its agenda on those of other organs. In the evolution of the human species to overcome dangers it was preferable to have a brain that functioned well than muscles at top efficiency. Preserving cognitive function is an absolute priority in extreme psycho-mental situations and it is better if glucose and oxygen, the fuel of mind and muscles, go towards thinking clearly rather than running fast. Also, in cases of chronic malnutrition or extreme famine, the brain is selfish, often preserving itself rather well in relative terms with respect to the rest of the body. However, the fact that, at least in part, the brain is prepared to accept some limitations when competing with muscles for the same resources, means that it performs a cost – benefit analysis and understands when it pays to accept restrictions in favor of muscles without which its survival would be impossible. The brain is so clever that it knows when it pays to be a little less clever.