ABSTRACT
On the average the human brain increased in size during the last 2.5 million years by one-millionth of a percent per generation. That may not sound like much, but added up, the change was from about 450 cubic centimeters to nearly three times that. Neurophysiologist Paul MacLean provided the evolutionary metaphor when he spoke of the “triune” nature of the brain, suggesting that the mammalian brain retains the anatomical and chemical features of our reptilian and early mammalian ancestors. Some basic truths have been known for centuries—truths acquired through thought and self-examination, many still undeciphered by scientists. Compared to other species the authors possess an unparalleled intellectual capacity. Often a blessing, still at other times it is a constraint of their other drives, making them most uncomfortable. The mind is the brain in action; the brain is an organ of the body.
