In the recent skirmishes over evolution, advocates who have pushed to dilute its teaching have regularly pointed to a petition signed by 514 scientists and engineers.

IN OPPOSITION Bruce Chapman, Discovery Institute president, top, and James M. Tour, chemistry professor at Rice, disagree with Darwin.

The petition, they say, is proof that scientific doubt over evolution persists. But random interviews with 20 people who signed the petition and a review of the public statements of more than a dozen others suggest that many are evangelical Christians, whose doubts about evolution grew out of their religious beliefs. And even the petition's sponsor, the Discovery Institute in Seattle, says that only a quarter of the signers are biologists, whose field is most directly concerned with evolution. The other signers include 76 chemists, 75 engineers, 63 physicists and 24 professors of medicine.

The petition was started in 2001 by the institute, which champions intelligent design as an alternative theory to evolution and supports a "teach the controversy" approach, like the one scuttled by the state Board of Education in Ohio last week.

Institute officials said that 41 people added their names to the petition after a federal judge ruled in December against the Dover, Pa., school district's attempt to present intelligent design as an alternative to evolution.

"Early on, the critics said there was nobody who disbelieved Darwin's theory except for rubes in the woods," said Bruce Chapman, president of the institute. "How many does it take to be a noticeable minority — 10, 50, 100, 500?"

Mr. Chapman said the petition showed "there is a minority of scientists who disagree with Darwin's theory, and it is not just a handful."

The petition makes no mention of intelligent design, the proposition that life is so complex that it is best explained as the design of an intelligent being. Rather, it states: "We are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life. Careful examination of the evidence for Darwinian theory should be encouraged."

A Web site with the full list of those who signed the petition was made available yesterday by the institute at dissentfromdarwin.org. The signers all claim doctorates in science or engineering. The list includes a few nationally prominent scientists like James M. Tour, a professor of chemistry at Rice University; Rosalind W. Picard, director of the affective computing research group at the Massachusetts Institute of Technology; and Philip S. Skell, an emeritus professor of chemistry at Penn State who is also a member of the National Academy of Sciences.

It also includes many with more modest positions, like Thomas H. Marshall, director of public works in Delaware, Ohio, who has a doctorate in environmental ecology. The Discovery Institute says 128 signers hold degrees in the biological sciences and 26 in biochemistry. That leaves more than 350 nonbiologists, including Dr. Tour, Dr. Picard and Dr. Skell.

Of the 128 biologists who signed, few conduct research that would directly address the question of what shaped the history of life.

Of the signers who are evangelical Christians, most defend their doubts on scientific grounds but also say that evolution runs against their religious beliefs.

Several said that their doubts began when they increased their involvement with Christian churches.

Some said they read the Bible literally and doubt not only evolution but also findings of geology and cosmology that show the universe and the earth to be billions of years old.

Scott R. Fulton, a professor of mathematics and computer science at Clarkson University in Potsdam, N.Y., who signed the petition, said that the argument for intelligent design was "very interesting and promising."

He said he thought his religious belief was "not particularly relevant" in how he judged intelligent design. "It probably influences in the sense in that it makes me very interested in the questions," he said. "When I see scientific evidence that points to God, I find that encouraging."

Roger J. Lien, a professor of poultry science at Auburn, said he received a copy of the petition from Christian friends.

"I stuck my name on it," he said. "Basically, it states what I believe."

Dr. Lien said that he grew up in California in a family that was not deeply religious and that he accepted evolution through much of his scientific career. He said he became a Christian about a decade ago, six years after he joined the Auburn faculty.

"The world is broken, and we humans and our science can't fix it," Dr. Lien said. "I was brought to Jesus Christ and God and creationism and believing in the Bible."

He also said he thought that evolution was "inconsistent with what the Bible says."

Another signer is Dr. Gregory J. Brewer, a professor of cell biology at the Southern Illinois University medical school. Like other skeptics, he readily accepts what he calls "microevolution," the ability of species to adapt to changing conditions in their environment. But he holds to the opinion that science has not convincingly shown that one species can evolve into another.

"I think there's a lot of problems with evolutionary dogma," said Dr. Brewer, who also does not accept the scientific consensus that the universe is billions of years old. "Scientifically, I think there are other possibilities, one of which would be intelligent design. Based on faith, I do believe in the creation account."

Dr. Tour, who developed the "nano-car" — a single molecule in the shape of a car, with four rolling wheels — said he remained open-minded about evolution.

"I respect that work," said Dr. Tour, who describes himself as a Messianic Jew, one who also believes in Christ as the Messiah.

But he said his experience in chemistry and nanotechnology had showed him how hard it was to maneuver atoms and molecules. He found it hard to believe, he said, that nature was able to produce the machinery of cells through random processes. The explanations offered by evolution, he said, are incomplete.

"I can't make the jumps, the leaps they make in the explanations," Dr. Tour said. "Will I or other scientists likely be able to makes those jumps in the future? Maybe."

Opposing petitions have sprung up. The National Center for Science Education, which has battled efforts to dilute the teaching of evolution, has sponsored a pro-evolution petition signed by 700 scientists named Steve, in honor of Stephen Jay Gould, the Harvard paleontologist who died in 2002.

The petition affirms that evolution is "a vital, well-supported, unifying principle of the biological sciences."

Mr. Chapman of that institute said the opposing petitions were beside the point. "We never claimed we're in a fight for numbers," he said.

Discovery officials said that they did not ask the religious beliefs of the signers and that such beliefs were not relevant. John G. West, a senior fellow at Discovery, said it was "stunning hypocrisy" to ask signers about their religion "while treating the religious beliefs of the proponents of Darwin as irrelevant."

Discovery officials did point to two scientists, David Berlinski, a philosopher and mathematician and a senior fellow at the institute, and Stanley N. Salthe, a visiting scientist at Binghamton University, State University of New York, who signed but do not hold conservative religious beliefs.

Dr. Salthe, who describes himself as an atheist, said that when he signed the petition he had no idea what the Discovery Institute was. Rather, he said, "I signed it in irritation."

He said evolutionary biologists were unfairly suppressing any competing ideas. "They deserve to be prodded, as it were," Dr. Salthe said. "It was my way of thumbing my nose at them."

Dr. Salthe said he did not find intelligent design to be a compelling theory, either. "From my point of view," he said, "it's a plague on both your houses."