American Scientist

HUMAN: The Science Behind What Makes Us Unique. Michael S. Gazzaniga. xiv + 447 pp., HarperCollins/Ecco, 2008. $27.50.

The fine intellectual adventure that is Michael Gazzaniga’s latest book, Human: The Science Behind What Makes Us Unique, opens with these sentences:

The great psychologist David Premack once lamented, “Why is it that the [equally great] biologist E. O. Wilson can spot the difference between two different kinds of ants at a hundred yards, but can’t see the difference between an ant and a human?” The quip underlines strong differences of opinion on the issue of human uniqueness.

The fact that Gazzaniga added the phrase in brackets suggests less than complete concurrence with Premack.

But since this “quip” is meant to frame the book, it’s interesting to recall that Wilson wrote in his most famous work, Sociobiology (1975), that “the development of human speech represents a quantum leap in evolution comparable to the assembly of the eukaryotic cell,” which is tantamount to calling it one of the most important events in the history of life. Ironically, Premack is best known for his elegant work teaching a keyboard-based symbolic language to chimpanzees. In reality, though, neither Premack nor Wilson—nor, certainly, Gazzaniga—doubts for a moment that humans are unique, and in more than just the sense in which any species is. Gazzaniga’s goal in Human is to find out what makes us so.

It’s a tall order, but a much more tractable one than the effort to explain, say, consciousness or free will. “What is the deal with humans?” (as Gazzaniga engagingly puts it) is an empirical question, and he is past master of the empirical materials, bringing to the task a 45-year career as a neuroscientist. A pioneer in the split-brain research that helped lay the foundations of our understanding of lateralization of function, Gazzaniga went on to make many discoveries on the frontier of brain imaging. He is editor of the comprehensive reference work Cognitive Neurosciences, now in its third edition, and is author of The Ethical Brain and many other books.

Here he is a helpful, amusing and modest guide. In the acknowledgments to Human he remembers his housemates in graduate school at Caltech, most of them physicists, as having been “all much smarter and wiser than I. . . . They thought hard about hard problems and they cracked many of them.”

Smarter, perhaps, in some ways; wiser, I doubt very much. Gazzaniga is about as wise as humans get, and wisdom is not about cracking hard problems. It’s about judgment in the face of immense complexity. However hard a puzzle in physics may be, the solution is in retrospect elegant and clear. Human uniqueness is not a puzzle in that sense; rather, it is a domain of understanding, and however much understanding we gain, a great deal will remain messy and unclear—which is where wisdom comes in.

I can only give a sketch here of the compendium of unique human traits considered in this rich and rewarding book. The human brain has tripled in size over the 6 or 7 million years that have passed since humans diverged from chimpanzees. A certain amount of reorganizing went along with that increase in size, increased lateralization being a prime example. Many genes and noncoding RNAs are expressed only in human brains, and many of those have to do with wiring up the brain during development. Bipedal walking freed our hands and allowed us to develop our unusually opposable thumbs for making tools. Our brains uniquely evolved for language and for an exceptional ability to think about the mental states of others.

We are the only species that can gossip, an important means of social control, and only a human will expend energy punishing a cheater who has cheated someone else. We are the only creatures that show disgust (hence our peculiar concern with purity), blush in embarrassment or shed tears of emotion. We display levels of empathy attained by no other species. We mentally imagine and simulate the actions and experiences (pain, shame) of others to a remarkable extent. Our lives are pervaded by aesthetic choices and preferences unknown to other species. We create art, religion and narrative, and we are self-aware to the nth degree. Only we can autocue, deliberately remembering and reminding ourselves of things.

These are just a few of the interesting points made, whose effect is to make you feel superior to all other species. You are, and you can enjoy sifting through the experimental evidence for that claim. Increasingly, these unique behavioral and psychological features are being tied to brain structure and function. Quite properly, Gazzaniga believes that these findings will lead in time to a coherent psychobiological theory, although his emphasis on modularity in the brain makes it possible to imagine a persistent lack of coherence.

One might have wished for more attention to animal field studies and cross-cultural comparisons, but even those are here to some degree. As most ordinary people throughout the world have long believed, humans are quite different from other animals. And Gazzaniga has not neglected the views of nonscientists. He asked a lot of acquaintances what they thought was unique about humans, and two of the responses he got are especially instructive.

A five-year-old said, “Animals don’t have birthday parties for themselves, you have to give them one.” And someone in an obstetrics clinic said, “I think at the core humans are no different from animals. We all have the bestial urges of expanding our hunting range, controlling resources, and spreading our DNA.” The five-year-old offers one of an infinite number of things that only humans do, something that is particularly salient for him. You might say that many of the things discussed in this book are like that birthday party—unique, but too particular to make much sense of—although many are more interesting and may in time figure in a theory of how we are fundamentally different.

The dour observer at the obstetrics clinic offers a small number of characteristics that we share with other animals. The difficulty is that these may be more important than the infinite number of characteristics that we don’t share. The question is not how we are fundamentally different, but how fundamental the differences are. That is what motivates many of us to consider what people have in common with chimpanzees, peacocks or, for that matter, ants. Countless unique human qualities were used by cultured Germans to murder millions. And only a human would advertise on the Internet to try to make a profit by bringing men seeking sex to an entrapped 13-year-old girl. In the core of our uniquely human brain is a set of structures brought down from our evolutionary past, and it is far from clear that they are really controlled by the newer structures. Too often, our unique human qualities seem to end up in the service of baser motives that we share with many other species.

But enough of the dark side. One of the special human qualities is taking pleasure in contemplating big scientific and philosophical questions. If you want to find out what we know today about how human brains and minds transcend those of other species, and particularly if you take pleasure in contemplating our superiority, you can’t do better than Michael Gazzaniga’s Human. And although I myself may spend more time contemplating the dark side, I completely agree with Gazzaniga when he says,

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.

If we are to turn our unique features into such a phase shift, surely we must thoroughly understand them, and this book is an excellent place to start.

Melvin Konner is Samuel Candler Dobbs Professor in the Department of Anthropology and the Program in Neuroscience and Behavioral Biology at Emory University. He is the author of, among other books, The Jewish Body (Shocken, 2009); The Tangled Wing: Biological Constraints on the Human Spirit, 2nd edition, revised and updated (Times Books, 2002); Becoming a Doctor (Viking 1987); and Childhood Evolving: Relationships, Emotion, and Mind (forthcoming from Harvard University Press).