Human
The Science Behind What Makes Us Unique
by Michael S. Gazzaniga
Ecco, 464 pp., $27.50

It's a familiar comic scene. A man is searching for something under a street lamp. A passerby approaches:

"What are you looking for?"

"My keys."

"Where did you lose them?"

"Back over there."

"Then why look for them here?"

"The light is better here."

Academic experts--economists, lawyers, philosophers, theologians--often seem to have the same attitude: Whatever you need you can find in their corner, where all the light is. Supply and demand, legal regulation, the Categorical Imperative, Original Sin can explain everything. Perhaps no discipline is more likely to claim explanatory omnipotence and unique objectivity than science. Before the altar of science, all other disciplines must bow. And its high priests are evolutionary biologists and neuroscientists: Everything about us, ultimately, can be explained by natural selection and the brain.

Am I being unfair? Only a bit. For an exemplar of this attitude, take Michael S. Gazzaniga's new book, Human: The Science Behind What Makes Us Unique. Don't let the subtitle fool you; it's not as if "science" is one among many branches of knowledge that shed light on what distinguishes us. No, Gazzaniga thinks that we can put away philosophical inquiry, poetic rumination, and prophetic revelation: Recent advances in neuroscience are finally providing us with what Gazzaniga regards as real answers to life's deepest questions, which (like everything human) are ultimately, he is absolutely sure, about biology.

In reality, Gazzaniga and his colleagues overreach and under-deliver. This is not to deny that science is making

Director of the SAGE Center for the Study of the Mind at the University of California at Santa Barbara, and a member of the President's Council on Bioethics, Gazzaniga is an authority on neuroscience, especially split-brain research. In Human he offers a useful one-stop shop on the latest scientific findings, even if his endless name-dropping and hedging of claims with conflicting theories make for a cumbersome read and leave some of his own conclusions elusive. Trying, too, is his overly conversational style: "How can one little change do so much damage? Take a deep breath. Blow it out slowly. OK, now you're ready." With proper editing, the text could have been half as long as it is.

Gazzaniga's main aim is simple: to show how human beings can be "hugely different" from other animals despite having "all of these connections with the biologic world, and .  .  . in some instances similar mental structures." The differences are the result of many small brain developments eventually reaching a biological tipping point, what Gazzaniga calls "a phase shift." After a tour of our brain's hemispheres and lobes, cerebral cortex and neocortex, cerebellum and corpus callosum, Gazzaniga concludes that "the human brain is a bizarre device, set in place through natural selection for one main purpose--to make decisions that enhance reproductive success."

He similarly explains human practices like the arts, noting that we alone make music as such. "It boils down to this: .  .  . Sensations and perceptions that have adaptive value .  .  . often become aesthetically preferred." Admitting (because scientific research confirms) that "art can put a smile on your face," Gazzaniga lets us in on the secret: We are smiling "because our cocky brain is pleased with itself, because it is fluently processing a stimulus, but you don't need to tell the artist that."