Anyone seeking reassurance about Iran's future as a peaceful, democratic nation would not do well to look to its current leaders, as President Mahmoud Ahmadinejad showed in his rambling, bizarre talk at Columbia University last month. Still, a rather more encouraging portrait emerges when you peruse Iranian demographic data. Iran is experiencing what you might call the reverse-Children of Men effect. Just like in the post-apocalyptic film, Iran is, increasingly, a society devoid of children. But the real-life outcome of this birth dearth is far less grim than the police state depicted onscreen. In fact, there's a good chance that declining fertility rates will usher in a new era of stability--an Iran that is bourgeois, secular, less like Children of Men's bombed-out Britain and more like ... Denmark.

In order for a society to maintain population levels, it needs a fertility rate that replaces both parents and allows for infant mortality: 2.1 children per woman (about what the current U.S. rate is). Traditionally, most Middle Eastern and Islamic societies have had a far higher rate; but, in recent years, the region's fertility rates have slowed--and nowhere is the drop more striking than in Iran. From 1950 through 1980, Iran had extraordinarily high fertility rates, between 6.5 and seven children per woman. During the '90s, however, the rate tumbled from 5.6 to 2.5, and, as of 2007, the rate is just 1.71. The population growth rate has undergone a similar plummet, from 3.2 percent in the mid-'80s, to 1.2 in 2001, to the current rate of 0.663. Essentially, between 1990 and 2000, Iran's demographic profile moved from the paradigmatic Third World model (high fertility rates, high growth) to the First World model.

The connection between fertility rates and political stability is still not fully understood, mostly because the human race has never, in its entire history, reproduced at below-replacement levels, and we simply don't have the longitudinal data to see what that could mean. Still, when you notice that some of the highest birthrates in the Islamic world are in places like Iraq, Somalia, Sudan, Afghanistan, and Gaza, whereas the world's lowest birthrates are in nations like Italy, Japan, and Germany, it's clear that Iran's lower birth rates could signal some unheralded, and very positive, changes.

How to understand Iran's sudden drop-off in population growth? Several factors come into play. In the long run, lower child mortality rates played some role, since parents weren't forced to play the odds by building large families. We should also recognize the Iranian government's post-1989 decision to expand family-planning arrangements--although similar attempts under the Shah's regime had produced nothing like the same epochal effects. But the clearest correlation is actually with Iran's somewhat surprising move toward gender equality in the 1990s. Despite the 1979 Islamic revolution, which overturned many of the displaced Shah's modernizations, the idea persisted that women should be educated and should be able to work. By 2000, women made up 60 percent of university entrants; today, they account for two-thirds of university graduates. The rate of female participation in the workforce in 1990 was 22 percent, only a little higher than Saudi Arabia's; by 2005, it was 41 percent. With growing numbers of women working (and, therefore, less available to parent a huge family), and with more financial options available to women outside of marriage, fertility rates inevitably dropped.

Obviously, Iranian culture doesn't bear many similarities to the world's other low-fertility belts, like Scandinavia and the northern Mediterranean. But there's some evidence that Iran may begin to resemble those regions once it begins to realize the effects of its baby bust.

It's well-known that economics dictate the sizes of families. Agricultural societies, for instance, have tended to produce high birth rates--with lots of extra hands for cow-milking and grain-harvesting. But family size can also affect the shape of an economy. If you don't have lots of kids to support you in your dotage, for instance, you begin to turn to the state for financial support, which means that you are invested in the state's continued stability. Conversely, when you have no children to support, your attitude toward posterity changes. With fewer heirs, you are more likely to spend money on yourself; increased spending buoys the economy; and, suddenly, industry is buzzing away.

And lower fertility rates might transform Iran even more fundamentally. Living in a nation where you are much less likely to have many children or grandchildren, and where many people will have none, you might find yourself losing the sense of continuity and tradition that makes religion work. Only by taking children out of the picture, in fact, can we appreciate how much of the institutional life of any religion revolves around passing traditions down to the young, through first communion classes, Koran training, or bar and bat mitzvahs. With these rituals--the cement of religious experience for many people--happening less frequently, your ties to church or mosque weaken.

Until now, European countries like Italy and Spain have provided the best examples of such a process. A priest who, in the 1970s, might have guided 1,200 children through the confirmation process in a year now deals with perhaps a tenth of that figure, meaning that the lifeblood of the church has been effectively shut off. As that change took effect, those nations became much readier to defy the church--for example, by legalizing abortion.

There's a corollary to this decay in traditional values. When you live in a country where you can expect to only have a few children at most (and where having no children is a viable option), your perception of marriage changes. Instead of viewing marriage mainly as a means to give birth to and raise socially functional children, you come to define it by other things, like companionship. And, as marriage becomes more about companionship than about children (more about maintaining this generation than about propagating the next), you may become more accepting of people who seek options outside of traditional marriage: for instance, all the gay Iranians who, according to Ahmadinejad, don't exist.

Demographic changes don't show their full effects for years--the children born into Iran's new social configuration won't graduate college until the 2010s and 2020s. But already Iranians have become familiar with expectations about gender, autonomy, and the individual that are very different from those offered by the clerical regime. Given another decade or so of uninterrupted development, trends make it very likely that Iran could approach high levels of stability and even political pluralism. Of course, that's if Ahmadinejad doesn't scotch it first.

Philip Jenkins is the author of God's Continent: Christianity, Islam and Europe's Religious Crisis.

By Philip Jenkins