Some Politics May Be Etched in the Genes
New York Times | June 21, 2005
By BENEDICT CAREY
Political scientists have long held that people's upbringing and experience determine their political views. A child raised on peace protests and Bush-loathing generally tracks left as an adult, unless derailed by some powerful life experience. One reared on tax protests and a hatred of Kennedys usually lists to the right.
But on the basis of a new study, a team of political scientists is arguing that people's gut-level reaction to issues like the death penalty, taxes and abortion is strongly influenced by genetic inheritance. The new research builds on a series of studies that indicate that people's general approach to social issues - more conservative or more progressive - is influenced by genes.
Environmental influences like upbringing, the study suggests, play a more central role in party affiliation as a Democrat or Republican, much as they do in affiliation with a sports team.
The report, which appears in the current issue of The American Political Science Review, the profession's premier journal, uses genetics to help answer several open questions in political science.
They include why some people defect from the party in which they were raised and why some political campaigns, like the 2004 presidential election, turn into verbal blood sport, though polls find little disparity in most Americans' views on specific issues like gun control and affirmative action.
The study is the first on genetics to appear in the journal. "I thought here's something new and different by respected political scholars that many political scientists never saw before in their lives," said Dr. Lee Sigelman, editor of the journal and a professor of political science at George Washington University.
Dr. Sigelman said that in many fields the findings "would create nothing more than a large yawn," but that "in ours, maybe people will storm the barricades."
Geneticists who study behavior and personality have known for 30 years that genes play a large role in people's instinctive emotional responses to certain issues, their social temperament.
It is not that opinions on specific issues are written into a person's DNA. Rather, genes prime people to respond cautiously or openly to the mores of a social group.
Only recently have researchers begun to examine how these predispositions, in combination with childhood and later life experiences, shape political behavior.
Dr. Lindon J. Eaves, a professor of human genetics and psychiatry at Virginia Commonwealth University, said the new research did not add much to this. Dr. Eaves was not involved in the study but allowed the researchers to analyze data from a study of twins that he is leading.
Still, he said the findings were plausible, "and the real significance here is that this paper brings genetics to the attention to a whole new field and gives it a new way of thinking about social, cultural and political questions."
In the study, three political scientists - Dr. John Hibbing of the University of Nebraska, Dr. John R. Alford of Rice University and Dr. Carolyn L. Funk of Virginia Commonwealth - combed survey data from two large continuing studies including more than 8,000 sets of twins.
From an extensive battery of surveys on personality traits, religious beliefs and other psychological factors, the researchers selected 28 questions most relevant to political behavior. The questions asked people "to please indicate whether or not you agree with each topic," or are uncertain on issues like property taxes, capitalism, unions and X-rated movies. Most of the twins had a mixture of conservative and progressive views. But over all, they leaned slightly one way or the other.
The researchers then compared dizygotic or fraternal twins, who, like any biological siblings, share 50 percent of their genes, with monozygotic, or identical, twins, who share 100 percent of their genes.
Calculating how often identical twins agree on an issue and subtracting the rate at which fraternal twins agree on the same item provides a rough measure of genes' influence on that attitude. A shared family environment for twins reared together is assumed.
On school prayer, for example, the identical twins' opinions correlated at a rate of 0.66, a measure of how often they agreed. The correlation rate for fraternal twins was 0.46. This translated into a 41 percent contribution from inheritance.
As found in previous studies, attitudes about issues like school prayer, property taxes and the draft were among the most influenced by inheritance, the researchers found. Others like modern art and divorce were less so. And in the twins' overall score, derived from 28 questions, genes accounted for 53 percent of the differences.
But after correcting for the tendency of politically like-minded men and women to marry each other, the researchers also found that the twins' self-identification as Republican or Democrat was far more dependent on environmental factors like upbringing and life experience than was their social orientation, which the researchers call ideology. Inheritance accounted for 14 percent of the difference in party, the researchers found.
"We are measuring two separate things here, ideology and party affiliation," Dr. Hibbing, the senior author, said.
He added that his research team found the large difference in heritability between the two "very hard to believe," but that it held up.
The implications of this difference may be far-reaching, the authors argue. For years, political scientists tried in vain to learn how family dynamics like closeness between parents and children or the importance of politics in a household influenced political ideology. But the study suggests that an inherited social orientation may overwhelm the more subtle effects of family dynamics.
A mismatch between an inherited social orientation and a given party may also explain why some people defect from a party. Many people who are genetically conservative may be brought up as Democrats, and some who are genetically more progressive may be raised as Republicans, the researchers say.
In tracking attitudes over the years, geneticists have found that social attitudes tend to stabilize in the late teens and early 20's, when young people begin to fend for themselves.
Some "mismatched" people remain loyal to their family's political party. But circumstances can override inherited bent. The draft may look like a good idea until your number is up. The death penalty may seem barbaric until a loved one is murdered.
Other people whose social orientations are out of line with their given parties may feel a discomfort that can turn them into opponents of their former party, Dr. Alford said.
"Zell Miller would be a good example of this," Dr. Alford said, referring to the former Democratic governor and senator from Georgia who gave an impassioned speech at the Republican National Convention last year against the Democrats' nominee, John Kerry.
Support for Democrats among white men has been eroding for years in the South, Dr. Alford said, and Mr. Miller is remarkable for remaining nominally a Democrat despite his divergence from the party line on many issues.
Reached by telephone, Mr. Miller said he did not see it quite that way. He said that his views had not changed much since his days as a marine, but that the Democratic Party had moved.
"And I'm not talking about inch by inch, like a glacier," said Mr. Miller, who makes the case in a new book, "A Deficit of Decency." "I'm saying the thing got up and flew away."
The idea that certain social issues produce immediate unthinking reactions comes through in other political research as well. In several recent studies, Dr. Milton Lodge of the State University of New York at Stony Brook has shown that certain names and political concepts - "taxes" or "Clinton," for example - produce almost instantaneous positive or negative reactions.
These intensely charged political reflexes are shaped partly by inheritance, Dr. Lodge said.
It may be the clash of visceral, genetically primed social orientations that gives political debate its current malice and fire, the study suggests.
Although the two broad genetic types, more conservative and more progressive, may find some common ground on specific issues, they represent fundamental differences that go deeper than many people assume, the new research suggests.
"When people talk about the political debate becoming increasingly ugly, they often blame talk radio or the people doing the debating, but they've got it backward," Dr. Alford said. "These genetically predisposed ideologies are polarized, and that's what makes the debate so nasty.
"You see it in people's eyes when they talk politics. You can hear it their voices. After about the third response, we all start sounding like talk radio on some issues."
The researchers are not optimistic about the future of bipartisan cooperation or national unity. Because men and women tend to seek mates with a similar ideology, they say, the two gene pools are becoming, if anything, more concentrated, not less.