WASHINGTON — By about 2-1, Americans accept the idea that “humans and other living things have evolved over time,” but as with so many issues these days, answers to that question have taken on a growing partisan cast.

According to a newly released survey by the Pew Research Center, six in 10 Americans say they accept the principle that species have evolved, while about one-third say that “humans and other living things have existed in their present form since the beginning of time.”

That overall division of American views has stayed fairly constant. But over the last few years, the gap between Democratic and Republican views has doubled.

In 2009, a majority of Democrats and Republicans took the evolution side of the argument, with 64 percent of Democrats and 54 percent of Republicans agreeing. In the latest survey, Democratic belief in evolution was about the same, 67 percent, but Republican support had fallen to 43 percent. A 10-point gap between supporters of the two parties had grown to a 24-point gulf.

What’s most striking is that the growing partisan gap seems to reflect politics rather than other factors. While Republican ranks include a high percentage of evangelical Christians and Democrats attract many secular voters, those religious differences didn’t explain the gap between the two parties. Even when Pew researchers factored out race, ethnicity and a person’s level of religious commitment, partisan differences on evolution remained, they found.

The differing views of Democrats and Republicans on evolution – and the fact that the two parties have diverged on the question – forms part of a consistent pattern: People who identify themselves as Republicans have become significantly more conservative on a range of issues in recent years, while people who identify as Democrats have become somewhat more liberal.

That trend of the two parties moving away from each other has affected views on the proper role of government, environmental issues and foreign policy, among other questions. Political scientists have cataloged a number of factors that could be influencing that change, including partisan media, a greater percentage of people actively engaged with political issues and the homogenization of views in both parties.

Beyond partisanship, the biggest gap in views on evolution involves religion. White evangelical Protestants and black Protestants are the two major groups in which majorities back the idea – traditionally associated with biblical fundamentalism – that humans and other species have existed in their current form throughout time. Majorities accept the idea of evolution in most other major religious groupings, including white, mainline Protestants; white Catholics; Latino Catholics; and the religiously unaffiliated.

Other notable divisions on the issue follow lines of age and education. Older Americans are less likely than younger ones to express a belief in evolution; people with only a high school education are less likely to believe in evolution than are college graduates. The survey was released Monday.

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