"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."