Over the next 500 years, however, everything changed.

By 700 A.D., the Roman Empire had vanished, Europe had become Christian, and the Near East and most of North Africa had become Muslim. Poor, uneducated and extremist Christian heretics and sectarians had dispersed around the Mediterranean basin, burning and terrorizing synagogues and pagan temples, before they themselves were overtaken in North Africa by Arab armies proselytizing a new, more austere religion. Meanwhile, Gothic tribes ravaged Europe.

Brown, in the course of a lifetime of scholarly work, gave a name to this pungent epoch in which the world gradually turned upside down: Late Antiquity.

Late Antiquity was dominated by vast civilizational changes, though many were not marked at the time. Late Antiquity appears full of drama only because we know its beginning and end. But on any given day during that half-millennium, the Mediterranean world might not have seemed dramatic at all, and few could have said in what direction events were moving.

The historical clock moves a great deal faster today. Thousands upon thousands of words have been written on the Arab Spring, the military rise of China, the tumult in the European Union, a nuclear Iran, and the chipping away of America’s post-Cold War hegemony.

But can we really discern any better than the denizens of Late Antiquity in what direction events are moving?

The erosion of America’s role as an organizing power has disoriented elites in Washington and New York whose own professional well-being is connected with America’s involvement abroad. And few developments have been more evocative regarding the sentiment of splendid isolation creeping once again through the American citizenry than Syria.

Syria is the Levant, the geographical core of Late Antiquity. Its disintegration, like the crumbling of Libya, Yemen and Iraq, along with the chronic unrest in Tunisia and Egypt, signifies not the birth of freedom but the collapse of central authority.

Rome could not save North Africa, and the United States will not save the Near East. For, as the opinion polls demonstrate, Americans have had enough of foreign military entanglements. Anarchy, perhaps followed by new forms of hegemony, will be the result.

If any individual life encapsulates Late Antiquity, it is that of St. Augustine, a Berber born in 354 in Algeria. In drifting from pagan philosophy to Manichaeism and finally to Christianity, St. Augustine straddled the worlds of classical Rome and the Middle Ages. His favorite poem was Virgil’s “Aeneid,” which celebrates the founding of Rome’s universal civilization. His great work, “The City of God,” writes scholar Garry Wills, sought to console Christians who were disoriented by the loss of Rome as the organizing principle of the known world. Rome, St. Augustine wrote, could never satisfy human hearts: Only the City of God could do that. Thus, as Rome weakened, religiosity intensified.

We are at the dawn of a new epoch that may well be as chaotic as that one — and that may come upon us more quickly because of the way the electronic and communications revolutions, combined with a population boom, have compressed history.

Consider that, in 1989, at the end of the Cold War, the United States was the unipolar military and economic colossus. Since then, the European Union has expanded throughout Central and Eastern Europe, promising an end to the furies of the continent’s past. The Middle East was benighted and illiberal, but at least it was quiescent, if only by its own dismal standards.

Then the world broke apart. An attack on the American homeland by Muslim extremists led to two large U.S. ground invasions in the Middle East, which, in turn, helped set the region in motion. Decadent autocracies later crumbled and conservative monarchies made unprecedented concessions, even if George W. Bush’s freedom agenda did not turn out as intended.

North Africa has since devolved into a borderless world of gangs, militias, tribes, transnational terrorists, antiterrorist expeditionary forces, and weak regimes gripped in stasis. The adjacent Levant erupted into low-intensity war, with only two strong legal entities left between the Mediterranean and the Central Asian plateau: a Jewish state and a Persian one (thus the centrality of Iran arguing for a rapprochement with the United States).

While this has happened, the European Union has begun to stagger. A debt crisis, negative growth and unseemly levels of unemployment have persisted as the welfare state — that signature moral accomplishment of postwar Europe — becomes in large measure unaffordable. The result is that the European Union itself has lost geopolitical force in Central and Eastern Europe, just as Russia has reemerged as authoritarian and powerful, thanks to hydrocarbon revenues. The map of Europe is changing from one uniform color back to divergent shades, with national identities undergoing a resurgence.

As for China — that demographic and geographical behemoth that has become the engine of world trade — after almost a third of a century of unprecedented growth, its economy is finally slowing down. China’s economy and military are still growing massively, but the future of the Middle Kingdom is less certain than it was just a decade ago. With ethnic minorities and Han Chinese both pining for more freedom amid fewer opportunities, it is possible that China might one day face a variation on the Soviet Union’s fate.

Authority, once so secure and conveniently apportioned across the globe, seems in the process of disintegrating into small bits, with sects and heresies — Salafists, cybercriminals and so on — entering from the side doors.

The United States still reigns supreme economically and militarily. Nevertheless, American power is increasingly stymied by these new and unpredictable forces.

Yet the postmodern version of Late Antiquity has just begun.

Amid this panorama of global unraveling and new forms of sovereignty (a phenomenon that St. Augustine experienced 1,600 years ago), tribes suddenly matter. Yes, tribes. They were the solution to checking the violence and undermining the religious extremists with their death cults in Iraq. They have been the dominating reality in Afghanistan. And when those reptilian regimes in North Africa and the Near East foundered, it was not democracies that immediately emerged, but tribes.

In St. Augustine’s world of imperial collapse, these ancient ties offered respite from disorder. But modernity was supposed to free us from the cloistered shackles of kinship. But the crumbling of central authority suggests that modernity is but a passing phase. Today, tribes with four-wheel-drive vehicles, satellite phones, plastic explosives and shoulder-fired missiles help close the distance between Late Antiquity and the early 21st century.

St. Augustine’s North Africa, now with its degraded urban conurbations of cracked brick and sheet metal, will see its population increase from 208 million to 316 million by 2050, putting pressure on both natural and man-made resources. As these millions move to the cities in search of jobs and connections, the political order will assuredly shift. Whatever arises may not be the states as they appear on today’s map. Indeed, what we consider modernity itself may already be behind us. The headlines between now and then will be loud and hysterical — as they are today in Syria — even as the fundamental shifts will at first be obscure.

For history is not only about convulsions, but about the ground shifting slowly under our feet.

In “The City of God,” St. Augustine revealed that it is the devout — those in search of grace — who have no reason to fear the future. And as the tribes of old now slowly come undone in the unstoppable meat grinder of developing-world urbanization, religion will be more necessary than ever as a replacement. Alas, extremist Islam (as well as evangelical Christianity and Orthodox Judaism in the West) may make perfect sense for our age, even as its nemesis may not be democracy but new forms of military authority.

Late Antiquity is useful to the degree that it makes us humble about what awaits us.


Robert D. Kaplan’s most recent book is “The Revenge of Geography.” He wrote this article for Foreign Policy magazine.