Excerpt from Us and Them by David Berreby, plus links to reviews, author biography & more

The important point is that any of these alternatives is possible. Mindless facts - who is a Tutsi, who is a Hutu, who has a veil, who lacks one - cannot predict what people will do. Human beings are unusually alike, compared to most species. We're also, each of us, unique. From those two facts, it follows that measurable, objective differences will always exist between any two groupings of people, and that any two groups, no matter how different, will be the same on many other measures. It will always be possible to find differences between this race and that one, this nation and those, people with this gene versus people without it. But not one of those facts will tell why you divided people into the human kinds you chose to analyze.

People who look at the traits of the kinds themselves, then, are posing the wrong questions. Do American Jews have higher average scores on certain academic tests than other Americans? Do African American marrieds have sex more often than others? Are Hispanics more likely to attend church? Maybe so, maybe not; but people don't start with data and then divide the world into Jews, African Americans, and Hispanics. It's the other way around. First we believe in those human kinds, and then, because we believe, we gather the data. To understand this aspect of ourselves, we don't need any more facts about human kinds. We need facts about human minds.

One way to find those facts is to study human kinds as if they were rules for thinking - methods of sorting out perceptions. You see a woman caring for her child and class her as a mother; you see a white-haired, stooped man and class him as an old person. That's a psychologist's approach. On the other hand, sociologists and anthropologists have looked at human kinds as rules for behavior - methods of knowing what people are supposed to do. In the right circumstances, knowing that someone is in the navy, or a doctor, or a devout Christian, tells you what he's likely to do, and how you should act in your turn. That knowledge serves as a bulwark against the force of ever-changing circumstances. Feeling hurried or stressed makes people less likely to help another person, but a reminder of their duties as members of a human kind can make them turn back. A military uniform, a Hippocratic oath, a bracelet that asks Christians "what would Jesus do?" - such tokens of membership make our actions more consistent than they would otherwise be. They remind us to look beyond the emotions of right here, right now, and act as members should. The navy is supposed to defend the nation, doctors to heal the sick, Christians to be Christlike, no matter what.

So these human kinds offer the joy of belonging to something larger than the little self; they let us thrill to a feeling of existence across centuries and continents, of being alive so long as "we," our kind, endure. The first type of human kind is a category based on traits ("white hair equals old person," for example). The second type is based on obligations ("Soldiers must serve the nation"). An institution of this second sort, we sense, must act consistently, even if individual members fail it. That's what defines human kinds of this second type: the things people do to belong.

That consistency makes it easy to think of this sort of human kind as if it were a person itself - a being with thoughts, plans, and feelings of its own. Nations have moods, schools have spirits, and a congregation can repent. You can say the navy has decided to seek more recruits next year. It's harder to come up with a sentence about how the world's mothers have decided to act.

Copyright © 2005 by David Berreby.  No part of this book maybe reproduced without written permission from the publisher.