Borgo Pio, a quiet street a few blocks from St. Peter's Square, is the Vatican's unofficial catwalk. Onlookers watch clusters of nuns from all over the world parade by in pink, blue, and brown habits.
But eavesdroppers won't hear them chattering in Italian or Latin, the Holy See's official languages. These nuns speak in their native tongues of Africa, Asia, and South America, where the fast-growing population of Roman Catholics has turned the global South into the church's new center of power.
As part of a broader trend of surging Christianity in the developing world, the rising tide - and rising clout - of Southern Catholics has already brought profound change to their faith. Morally and theologically conservative, respectful of authority, poor but full of zeal, they are everything that European Catholics are not.
Now that John Paul II has died, some Catholics are asking: Shouldn't the next pope represent this class of Catholics, which makes up two thirds of the Vatican's 1.1 billion strong flock?
"The South is increasingly the center of energy of Christianity," says Vatican expert John Allen. "There is a strong current that would regard a pope from the developing world as the most suitable leader now."
Among the names of cardinals listed as likely successors, three or four are from the developing world. A pope from the South, analysts say, would probably uphold the church's teachings opposing abortion, contraception, married clerics, and same-sex unions.
"Christians are facing a shrinking population in the liberal West and a growing majority of the traditional rest," says Philip Jenkins, author of "The Next Christendom: The coming of global Christianity."
Christianity, and Catholicism in particular, are booming in the global South. The rise is so great, in fact, that Christendom's so-called center of gravity - the point on the globe where roughly the same number of believers live to the north, south, east, and west - is shifting ever further from Rome, not to mention Jerusalem, where Christianity started.
Today, according to a trajectory mapped by the Center for the Study of Global Christianity, based in South Hamilton, Mass., the demographic heart of the Christian world has shifted to Timbuktu, in the mostly Muslim African nation of Mali.
It won't be there for long. As the numbers of African Christians multiplies, and as Europe's churches continue to empty, by 2100, the center of gravity will have pushed deeper south, to Sokoto, Nigeria. By then, experts estimate, there will be three times more Christians in the global South than in the North.
"It's a shock to see how fast this center of gravity is moving," says Todd Johnson, director of the Center for the Study of Global Christianity. "The growth of Christianity in Africa today is faster than it has been at any time in Christian history."
Since 1900, the number of Christians in Africa has jumped to 390 million from 8.7 million, an increase of more than 4,400 percent. By 2025, Africa's pews are expected to seat almost 600 million believers.
By contrast, in Europe, the only part of the world where Christianity is on the decline, the number of Christians (including Russians) is set to drop by 18 million by 2025. There are officially 531 million Christians in Europe, making them still the largest single group in the world.
But only 10 percent of them go to church on a regular basis.
There is "increasing tension" between the liberal North and the "surging Southern religious revolution," Jenkins says.
Catholicism has followed roughly the same population shift as Christianity as a whole during the past century, according to Johnson.
Despite losing believers to a new wave of evangelical churches taking Latin America by storm, Catholicism has continued to grow there in large part simply because of high birth rates.
In Asia and Africa, meanwhile, the rapid rise of Catholicism is fueled as much by birth rates as it is by the discovery of the faith.
In 1900, 68 percent of the world's Catholics were in Europe; today just 25 percent are, according to the Center for the Study of Global Christianity.
Latin American Catholics, meanwhile, now make up 43 percent of the world's total, while Catholic Asians now make up 11 percent. And Africa, which had 1 percent of Catholics worldwide in 1900, is now home to 13 percent.
For many, Christianity has already reached a historic turning point. Archbishop John Onaiyekan, of Abuja, Nigeria, suggested recently that "priests from places like Nigeria can reevangelize Europe." Hundreds of years after Europeans began evangelizing the world, African missionaries are now traveling to the Old Continent to revive the faith.
Cardinal Francis Arinze of Nigeria, a charismatic Vatican diplomat, is a much touted "papabile," one who could be pope. But few believe the Catholic Church is ready for a black pope.
Cardinals Claudio Hummes of Brazil, and Jorge Mario Bergoglio of Argentina are perhaps more-probable Southern contenders. A few outspoken Southern cardinals have indicated in the past that a pope from the developing world is what the Catholic Church badly needs.
"The world is looking forward to an Asian or Latin American pope," Cardinal Telsphore Placidus Troppo, one of India's three cardinal electors, said in December 2004.
But the arithmetic of the conclave of cardinals reveals the limits of the developing world's clout. For instance, even though 43 percent of the world's Catholics live in Latin America, there are just 21 Latin American cardinals among the 117 eligible to elect the next pope. Even if all Southern cardinals united behind one candidate, their 45 votes would fall short of the needed two-thirds majority.
Some experts expect the papacy to return to an Italian - a tradition that held for nearly five centuries before John Paul II.
"The world changes, but the church doesn't," said a Vatican source, asking not to be named.