2 percent of the body but consumes more than 20 percent of its energy. Extra gray matter is useful only if it enables an animal to get enough extra calories to power it, and scientists didn’t understand how the brain was paying for itself.
Dunbar eventually concluded that the large brain did not evolve to deal with the physical environment, but rather with something even more crucial to survival: social life. Animals with bigger brains had larger and more complex social networks.
the smartest nonhuman primates can mentally project perhaps twenty minutes into the future—long enough to let the alpha male eat, but not long enough for much planning beyond dinner. (Some animals, like squirrels, instinctively bury food and retrieve it later, but these are programmed behaviors, not conscious savings plans.) In one experiment, when monkeys were fed only once a day, at noon, they never learned to save food for the future.
Much of self-control operates unconsciously. At a business lunch, you don’t have to consciously restrain yourself from eating meat off your boss’s plate.