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Close-up of a voting machine
Close-up of a voting machine at the U.S. National Museum of American History.

Photograph by Scott J. Ferrell, Congressional Quarterly via Getty Images

Maggie Koerth-Baker

for National Geographic News

Published March 3, 2010

Your apelike ancestors probably aren't top of mind when you enter the polling booth. But a new study suggests that human evolution may have a big influence on whether you're liberal or conservative—not to mention how smart you are, whether you believe in God, or whether you've got a cheatin' heart.

It's all linked to the evolution of intelligence, says author Satoshi Kanazawa, an evolutionary psychologist at the London School of Economics and Political Science.

(Also see "Future Humans: Four Ways We May, or May Not, Evolve.")

Kanazawa's theory is that intelligence—particularly our ability for on-the-spot problem solving and reasoning—arose as an adaptation to deal with the unusual and unexpected, such as a sudden forest fire.

Since disasters like that are rare in daily life, responding to them wouldn't likely be something our ancestors were hard-wired to "know" how to do. Surviving the fire required both the ability to think up a new behavior, and the willingness to try it out.

Passed down via genetics, those two traits are still the calling cards of an intelligent brain—expressed as a tendency toward adopting nontraditional social values and preferences, Kanazawa says in his new study, published in the March 2010 issue of Social Psychology Quarterly.

As a result of their iconoclastic ancestry, he suggests, people with higher levels of intelligence are more likely to adopt social values and behaviors that are relatively new to human life—liberalism, atheism, staying up late, and (for men) monogamy, for example.

This tendency toward iconoclasm stems from smart people's brains being better adapted to dealing with new situations, according to Kanazawa.

(Related: "Did Discrimination Enhance Intelligence of Jews?")

Liberals Are Smarter Than Conservatives?

Kanazawa's evidence is in the National Longitudinal Study of Adolescent Health, or Add Health, which has been tracking the same group since 1994.

The study used a picture-based vocabulary test to estimate the IQ of participating teenagers. Seven years later, the same people were asked about their religious and political beliefs.

People who later admitted to being "not at all religious," and who classified themselves as "very liberal" politically had higher IQ scores as teenagers than those who were "very religious" and "very conservative."

The difference isn't huge. Only 11 points, on average, separate the liberal from the conservative, for instance. But Kanazawa believes it's significant.

"Liberalism"—which Kanazawa defines, in part, as caring about the well-being of vast numbers of people you'll never meet—"is a very new thing for humans," he said.

"Historically, humans cared about the welfare of immediate family and friends but not complete strangers."

(See "Was Darwin Wrong?" from National Geographic magazine.)

Faulty Evidence?

The new study is intriguing, if speculative, other psychologists say.

"Kanazawa has done interesting work, but there are other hypotheses out there for the evolution of intelligence that are equally interesting," said Douglas Detterman, a psychologist at Case Western Reserve University and editor of the journal Intelligence.

For instance, other researchers have advanced the theory that intelligence arose as a way of competing for sex. If that's the case, Kanazawa's conclusions only make sense if, say, being liberal or atheist also makes you more sexually attractive. (Take a Darwin quiz.)

Also, the IQ test may not be the best evidence for Kanazawa's ideas, said Stephen Ceci, professor of developmental psychology at Cornell University.

IQ tests can be a good way to measure intelligence, he said, particularly when the results are controlled for differences in education and socioeconomic status, as Kanazawa's were.

But the Add Health method for measuring IQ—via picture vocabulary questions—doesn't necessarily tell you anything about the right kind of intelligence, Ceci said. "They're a better measure of crystallized intelligence, which you acquire through school and culture. That kind of intelligence is not primarily genetic."

If a preference for nontraditional values is in fact an evolutionary adaptation, Ceci said, you could only determine that using an IQ test that measures problem solving and reasoning skills that are not explicitly taught—such as a puzzle-based assessment.

(Related: "Human Genome Shows Proof of Recent Evolution, Survey Finds.")

Study author Kanazawa appears to agree that his evidence could be better, saying, "Professor Ceci's comment is very well taken."

In fact, Kanazawa recently finished compiling data from the National Child Development Study (NCDS), which uses 11 different cognitive tests, administered at three different ages.

The NCDS is a much sturdier way to measure innate intelligence, Kanazawa said, and he'll be using the newly compiled data to try to replicate his findings.

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