This essay is the culmination of forty-five years as a psychiatrist investigating the relationship between severe mental illnesses and human evolution. I have concluded that the most important changes leading to our evolutionary success occurred inside the mind. Upright posture, large molar teeth, opposable thumbs, large brains, and the onset of culture were additive responses to the evolution of what MOTIVATED early humans. The most important audience for this book are those who have experienced serious mental illness in themselves or loved ones. The inner experiences of major depression, panic disorder, schizophrenia, and bipolar disorder are shown to derive from the breakdown of normal emotions we all know intimately. These everyday feelings are ancient, have played a central role in our evolution, and thus can be viewed as "emotional fossils." Stigmatized for centuries, mental illnesses are revealed to be the price we pay as a species for the extraordinary mental capacities that make us human. Short and explicitly written to be accessible, this essay interprets the scientific findings of human evolution in accordance with an evolving mind.