Washington (CNN) – A growing partisan divide is emerging between Republicans and Democrats on human evolution, according to a poll by the Pew Research Center.
Forty-eight percent of self-identified Republicans told Pew in a study released Monday that they believe humans "existed in their present form since the beginning of time." On the contrary, 43% of Republicans said the opposite, that they believed humans "have evolved over time."
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That is a sizable shift from 2009, the last time Pew asked the question. In that survey, a majority of Republicans – 54% – told Pew they believed in human evolution.
The percentage of Democrats who believe in human evolution, on the other hand, grew in the last four years. Two-thirds (67%) said they believe in human evolution, compared to 27% who said they didn't.
In 2009, the number of Democrats who said humans evolved over time was 64%.
"I didn't expect to see that kind of shift," said Cary Funk, the senior researcher at Pew who oversaw the study. "I think it basically fits with a pattern of growing polarization. And we see that on some other science issues."
Despite the fact that most scientists agree that the Earth is 4.5 billion years old, the universe is 13.7 billion years old and that humans have evolved over time, not everyone agrees. According to the Pew poll, 60% of Americans believe humans have evolved over time, compared to 33% who said they have not – a number that has remained constant since 2009.
The latter belief is particularly strong among white evangelical Protestants, many of whom read the Biblical creation account in Genesis literally: The six days in the account are strictly 24-hour periods and leave no room for evolution. Sixty-four percent of white evangelical protestants and 50% of black protestants believe humans have not evolved, according to the poll.
The idea of creationism has been scorned by the mainstream scientific community since shortly after Charles Darwin introduced "The Origin of Species" in 1859. By 1880, The American Naturalists, a science journal, reported nearly every major university in America was teaching evolution.
For Funk, the Republican shift was surprising and led the researchers to check the numbers by controlling the data against racial and ethnic divides between the two parties. Even still, Funk said, the divide on human evolution between Democrats and Republican, as well as the changes in Republican beliefs, persisted.
"Differences in the racial and ethnic composition of Democrats and Republicans or differences in their levels of religious commitment do not wholly explain partisan differences in beliefs about evolution," read the Pew report. "Indeed, the partisan differences remain even when taking these other characteristics into account."
The Pew report is based on telephone interview conducted between March 21 – April 8, 2013 with a sample size of 1,983 adults. The survey has a sampling error of plus or minus three percentage points.