PROVO — The window for changes to Philip Jenkins' last book on the future of Christianity closed on Sept. 10, 2001. The terrorist attacks the following day did nothing to dilute the chapter titled "The Next Crusade," about the potential for violence between Christianity and Islam over the next four decades.

Jenkins spoke at Brigham Young University recently because his book "The Next Christendom — The Coming of Global Christianity" is the book of the semester at BYU's Kennedy Center for International Relations. Jenkins said explosive growth in Christian populations in Africa and Latin America will move the heart of Christianity south by 2025.

By 2050, he says, Africa and Latin America will pass Europe as the leaders in Christian population, and Asia will surpass North America, altering the religion significantly and remaking world politics.

"The era of Western Christianity has passed within our lifetimes," Jenkins said, "and the day of Southern Christianity is dawning."

And as the numbers of Christians and Muslims explode side-by-side in some countries on those continents, Jenkins said there is already evidence of the potential for conflict.

"Am I predicting religious wars in the future? No, I'm describing them now," he said, referring to recent clashes in Asia and Africa.

In the past 11 years, Serbian Christians have massacred Muslims in Bosnia and Muslims have killed Christians in the Sudan. Fighting between members of the two religions in Nigeria, where they are nearly equal in numbers, began to escalate in the late 1990s. And Jenkins, during an interview, said the next year's federal elections could cause a "a big religious breakdown."

"While we can imagine any number of possible futures," Jenkins wrote in his book, "a worst-case scenario would include a wave of religious conflicts reminiscent of the Middle Ages, a new age of Christian crusades and Muslim jihads. Imagine the world of the 13th century armed with nuclear warheads and anthrax."

Jenkins, a professor of history and religious studies at Penn State University, said the religions can co-exist and urged political leaders and diplomats to include religious considerations and leaders in deliberation and diplomacy, a point also made at BYU recently by Rabbi David Rosen, who spoke at the J. Reuben Clark Law School.

Rosen helped broker the 2002 Alexandria Declaration of the Religious Leaders of the Holy Land, in which five rabbis, five Christian leaders and five Muslim leaders decried violence as a violation of their religions.

Rosen said the perception that violence between Israelis and Palestinians is based on religion is wrong and harmful because it isn't about theology, but he insisted that religious leaders must be included in the peace process.

"You cannot eliminate the religious dimension from the political process," Rosen said, pointing to the unraveling of the Camp David and Oslo accords because religious leaders on both sides felt sidelined and extremists reacted violently.

Jenkins focused much of his lecture at BYU on the way the shift south will change Christianity, drawing from his new book, "The New Faces of Christianity — Believing the Bible in the Global South."

He said the Old Testament resonates in Third World nations because it is familiar. Africans understand prophecy, blood sacrifice, healing, supernaturalism, nomadism and paganism.

"The Old Testament describes their world," Jenkins said. "It's a very poor world. When you read the scriptures through Third World eyes, when you read the scriptures through hungry eyes, you realize how much of scripture relates to food. They have lived that."

He also called this the greatest age of Christian hymn writing, though few Westerners realize it because the hymns are in Hindu or in African tongues.

BYU world religions professor Roger Keller said Jenkins' books and lecture globalized the findings of Rodney Stark and Roger Finke in another book Keller recently read, "The Churching of America, 1776-2005 — Winners and Losers in Our Religious Economy."

Stark and Finke said the religious groups flourishing in the United States are those that demand more of their members and thus also offer something otherworldly that is very real and tangible to them.

These are issues for a proselyting religion such as The Church of Jesus Christ of Latter-day Saints, which owns BYU, because in Africa and Latin America, the greatest successes belong to groups that adapt to the cultures.

"We are learning or struggling some with that (in the LDS Church)," Keller said. "I know that (among LDS Church leaders) there have been serious discussions about what you have to export with the gospel. Baseball or basketball are not necessary, for example. I'm looking forward to the day when half the hymn book in India is Indian hymns using their tonal scales. I don't think they have to use our tonal scales to be spiritual."

The LDS Church grew so rapidly in the mid-1900s that Stark predicted it was possible for the church to have 250 million or more members by 2080. Now growth has leveled off to about 3 percent per year, with convert baptisms dropping steadily from 321,000 in 1996 to 243,000 last year.

Part of the slowing is intentional, as LDS Church President Gordon B. Hinckley has focused efforts in developing countries on retaining new converts and strengthening congregations.

"We'll never get away from the central hierarchy," Keller said, "but maybe we'll get away from requiring white shirts and ties for passing the sacrament. I think we're trying to learn how to work with other cultures. I think it's a new frontier for us right now."