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

Then, too, even a trivial human kind, defined by nothing more consequential than what people buy, can call up the intense emotions supposedly reserved for the serious tribes. That's what happened to one owner of a Porsche 911 sports car after he learned that the company had started to make sport utility vehicles. "Every SUV I've seen is driven by some soccer mom on her cellphone," he told a reporter. "I hate these people, and that Porsche would throw me into that category made me speechless. Just speechless."

Speechless! Kind-mindedness can be downright embarrassing. It lacks gravitas. It goes its own way. That's a good reason for scientists to shun the whole business. Who wants to be yelled at for supposedly equating race and religion with soccer hooligans and Porsche owners?

And yelling there will be. Aside from being messy conceptually, human kinds are sticky, emotionally. There's no place to stand outside of them, to look on them without feeling. All people are members of human kinds, and so whenever human kinds are the subject, the conversation feels personal. Reading the news in the morning, we're pained to learn that studies show "our people" are fat, or do poorly on math tests, or don't spend enough time with their children. We're proud and pleased when our athletes win at the Olympics, or when we read that our troops acted nobly. We're scared when we learn about a human kind that threatens ours. Presented with any list of human kinds - in a newspaper article, on a Web site, on a restaurant place mat with the Chinese zodiac printed on it - always, inescapably, a part of us wonders: Which one fits me? Am I metro or retro? Gobbler or nibbler? Snake or horse? Human-kind thoughts are impossible to separate from your feelings about yourself.

Some scientists' distaste for human kinds as a research subject may come from a desire to avoid thoughtless, factless passion. They want to stay within the framework of science, confining themselves to matters their methods can address. Outside that realm, many feel, science can't venture, and scientists shouldn't. As the great physicist Richard Feynman said, "A scientist looking at a non-scientific problem is just as dumb as the next guy."

And what could be less like science than talk of race and nation and religion, family and sexual identity and sports - veined as it always is with vague words and strong emotions? Human kinds are gnarly, demanding, and perplexing, like intimate life. If a human kind matters, people will talk of it as if it were a family: the "brothers and sisters" of houses of worship, union halls, and political rallies; the "children of God" of the preachers; the "brothers" who went through war, or college, or prison together; the friendly office with the family atmosphere.

This doesn't mean, of course, that we think of such groupings as literal families, or that we wish they were. If you call your sexual partner "baby," it doesn't indicate you'd rather have sex with an infant. But it is an expression of something everyone learns as groups sort themselves on the playgrounds of early childhood: being part of a human kind, or excluded from one, can alter your life. Such consequential changes, wrought by being in a human kind, can be conscious and deliberate, as it is for Christians who ask themselves, "What would Jesus do?" Sometimes, though, the effects of human-kind thinking take place outside awareness. In one experiment, for example, Asian American women students at Harvard who were reminded that they were Asian did better on a math test than Asian American women who were reminded that they were women.

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