This is a brilliant overview of all the research work that has gone into deciding what makes human beings unique (if we are, but the evidence is strong that we are, among Earth's creatures).

It covers everything from the evolution of our social awareness and moral standards to the debate over whether intelligence must remain embodied -- that is, do you need a physical body to develop the kind of consciousness and intelligence that humans have? -- or whether it can be disassociated from the flesh and incorporated into a computer or robot of some type (the Ray Kurzweil approach).

It also explores what role the arts play in human life and where they may have come from, in an evolutionary adaptive sense, and looks at the raging debate over how consciousness arises (one leading theory today is that our sense of self-awareness actually emerges from several different modules of the brain that supply different parts of it).

Gazzaniga, director of the SAGE Center for the Study of the Mind at UC-Santa Barbara, is an erudite and occasionally funny writer who seems to have consulted every relevant study under the sun, and footnotes them extensively.

As someone who regularly produces story ideas for myself and the rest of my newspaper, I found that I filled several small notebook pages with possible articles from ideas in this book. Just two: At Meiji University, Tohru Suzuki and his colleagues are developing humanoid robots that imitate human actions they observe, record the facial and vocal emotions humans are expressing and imitate them as well and can even tell when a human points to an object what emotional salience he attaches to it; Malcolm Donald, a theoretical neuroscientist, believes our language and culture came from our evolving fine motor control, because that is what enabled us to produce gestures, which were the forerunners of language, which is the bedrock of culture. And on and on.

If you are looking for one book that gives you a cook's tour of the human brain, this would be an excellent choice.

In his conclusion, Gazzaniga writes: "Maybe those people who see humans as only slightly different from the rest of the animals are right. Just like other animals, we are constrained by our biology. We may not have the capacity to be any better than their worst appraisal. But the ability to wish or imagine that we can be better is notable. No other species aspires to be more than it is. Perhaps we can be. Sure, we may be only slightly different, but then, some ice is only one degree colder than liquid water. Ice and water are both constrained by their chemical composition, but they are very different because of a phase shift."

And humans, he persuasively argues, have undergone a phase shift from their nearest primate relatives -- and may do so again in the future.