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.