A Vatican-backed conference on evolution is under attack from people who weren't invited to participate: those espousing creationism and intelligent design.

The Discovery Institute, the main organization supporting intelligent design research, says it was shut out from presenting its views because the meeting was funded in part by the John Templeton Foundation, a major U.S. nonprofit that has criticized the intelligent design movement.

Intelligent design holds that certain features of life forms are so complex that they can best be explained by an origin from an intelligent higher power, not an undirected process like natural selection.

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Organizers of the five-day conference at the Pontifical Gregorian University said Thursday that they barred intelligent design proponents because they wanted an intellectually rigorous conference on science, theology and philosophy to mark the 150th anniversary of Charles Darwin's "The Origin of Species."

While there are some Darwinian dissenters present, intelligent design didn't fit the bill, they said.

"We think that it's not a scientific prospective, nor a theological or philosophical one," said the Rev. Marc Leclerc, the conference director and a professor of philosophy of nature at the Gregorian. "This makes a dialogue very difficult, maybe impossible."

He denied the decision had anything to do with Templeton's funding for the conference. "Absolutely not. We decided independently within the organizing committee, in total autonomy," Leclerc said.

The Pennsylvania-based Templeton Foundation, which has an estimated endowment of $1.5 billion and awards some $70 million in annual grants, seeks to fund projects that reconcile religion and science.

At least three of the conference speakers, including two members of its scientific committee, serve on the Templeton Foundation's board of advisers.

The Templeton representative at the conference, Paul Wason, director of the foundation's science and religion programs, said the grant had no strings attached.

"They sent us the proposal after they had most of the speakers already. We decided to make the grant in part because it is a really good speakers' list," he said.

The foundation has criticized intelligent design in the past and says on its Web site that it doesn't support any research or programs that "deny large areas of well-documented scientific knowledge."

An official with the Pontifical Council for Culture, which is backing the conference, said the Templeton grant covered almost half the meeting's budget. But the official, the Rev. Tomasz Tramfe, also denied Templeton put any restrictions on who was invited to speak.

The Discovery Institute's president, Bruce Chapman, said he wasn't surprised intelligent design was kept out.

But in an e-mail, he said the conference didn't speak for the Vatican as a whole, where he said evolution and intelligent design "remain in serious and fruitful dialogue."

Indeed, some influential cardinals have indicated they support intelligent design, including Cardinal Christoph Schoenborn of Vienna, a close collaborator of Pope Benedict XVI.

In addition to intelligent design, creationism has come under disdain at the conference.

In his opening address, Cardinal William Levada, head of the Congregation for the Doctrine of the Faith, spoke dismissively of fundamentalist Christians in the U.S. who want schools to teach biblical creationism alongside, or instead of, evolution.

Muslim creationists also complained about the conference.

Oktar Babuna, a representative of a prominent Turkish creationist, Harun Yahya, was denied the right to speak at the opening session Tuesday.

Participants took the microphone away from Babuna when, during a question-and-answer session, he challenged them to give proof of transitional forms of animals in Darwinian evolution.

Organizers said he hadn't formulated a question and was just stating his point of view.

Babuna said afterward that the conference was clearly undemocratic. A statement from Yahya said, "Although there are discussion parts, they want this discussion to be one-sided."

Vatican teaching holds that Roman Catholicism and evolutionary theory are not necessarily at odds. The church under Benedict has been trying to stress that, along with its overall belief that there is no incompatibility between faith and reason.

Pope John Paul II articulated the church's position most clearly in a 1996 address to the Pontifical Academy for Sciences, saying the theory of evolution is "more than a hypothesis."