Less than half of all Republicans believe in human evolution, a significantly smaller percentage than in 2009, according to a new study.

Democratic belief in evolution, meanwhile, has increased slightly during the same period, the Pew Research Center analysis shows.

Today, 43 percent of Republicans and 67 percent of Democrats say "humans and other living things have evolved over time," a difference of 24 percentage points, Pew says. In 2009, 54 percent of Republicans and 64 percent of Democrats said humans evolved over time, a 10-point gap.

Overall, 60 percent of Americans believe in evolution, while 33 percent reject the idea, saying that "humans and other living things have existed in their present form since the beginning of time," the poll says. The share of the general public who say that humans have evolved over time is about the same as it was in 2009, when Pew Research last asked the question.

About half of those who express a belief in human evolution say that it's "due to natural processes such as natural selection." But 24 percent of Americans believing in evolution say that God or a supreme being played a role in evolution.

Evolution beliefs differ strongly by religious group. A majority of white evangelical Protestants — 64 percent — and 50 percent of black Protestants say that humans have existed in their present form since the beginning of time. But in other large religious groups, a minority hold this view, with 78 percent of mainstream Protestants and 68 percent of white non-Hispanic Catholics saying that humans and other living things have evolved. Seventy-six percent of the religiously unaffiliated say the same.

Fifty-three percent of Hispanic Catholics say humans have evolved, while 31 percent reject the idea.

The nationwide telephone survey of 1,983 adults was conducted in March and April, although the results weren't released until Monday. The margin of error is plus or minus 3 percentage points.