In another sign of the deep and growing partisan divide, American views on evolution are growing apart, as well.

Less than five years ago, 54 percent of Republicans and nearly two-thirds of Democrats said the human species evolved over time. Today, however, the share of Republicans adhering to modern theories of human evolution has dropped significantly – to 43 percent – while the number of Democrats has climbed to 67 percent, though within the sampling error range, according to a Pew Research Center study of the public’s views of human evolution, released Monday.

"The gap is coming from the Republicans, where fewer are now saying that humans have evolved over time," said Cary Funk, a senior researcher at the Pew Research Center's Religion & Public Life Project, according to Reuters.

As a whole, 6 of 10 Americans say they believe that “humans and other living things have evolved over time,” with a third rejecting evolution altogether, saying that “humans and other living things have existed in their present form since the beginning of time.”

And while the views of most sub-groups have remained relatively unchanged since 2009, the change among those identifying themselves as Republicans is somewhat curious.

Even when Pew researchers attempted to factor out the influence of education, race, and levels of religious commitment, the poll still showed a spike in partisan differences.

"It's an intriguing finding that is suggestive of greater polarization," said Mr. Funk, who conducted the analysis of the poll, according to NBC news.

When Pew began to measure differences in how those in each party feels about certain value-oriented questions in 1987, the average gap between Democrats and Republicans was 10 points. By 2012, this difference was 18 points.

And these differences have grown mostly during the Bush and Obama presidencies. Until 2002, the average difference in values fluctuated between 9 and 11 points. This jumped to 14 points in 2003, however, then up to 16 points in 2009, and then 18 points in 2012. The poll had asked the same questions in the same way for 25 years, Pew researchers say.

Those with the most pronounced skeptical views on human evolution remain white evangelical Protestants, who are a potent force in conservative politics and a key base of support for the tea party movement.

“God's word is true. I've come to understand that. All that stuff I was taught about evolution and embryology and the big bang theory, all that is lies straight from the pit of hell," said tea party Rep. Paul Broun (R) of Georgia in a 2012 speech. “It's lies to try to keep me and all the folks who were taught that from understanding that they need a savior.”

Almost two-thirds of white evangelical Protestants say humans existed in their present form since the beginning of time, while nearly 8 in 10 “mainline” Protestants believe in evolution. In fact, though half of black Protestants are skeptical of human evolution, no other religious group in the country has a majority doubting human evolution.

Scholars point out, too, that Darwinism was one of the galvanizing issues in the evolution of contemporary evangelical Protestantism. As Protestants began to grapple with a changing modern world in the early 20th century, “mainline” and Evangelical divisions began.

Get the Monitor Stories you care about delivered to your inbox. By signing up, you agree to our Privacy Policy

In a series of essays called “The Fundamentals” from 1910 to 1915, conservative Presbyterians, mostly, railed against the “decadence of Darwinism” and modern scholarship. The term “fundamentalism,” now used as a fungible catch-all for most any conservative religious group, derives from these famous tracts.

And after the Scopes trial in 1925, which began to turn public opinion toward the acceptance of teaching evolution, conservative evangelicals were not a major force in public up to the 1970s, reemerging with the election of Ronald Reagan and becoming one of the more significant forces in American politics.