All is for the best in this best of all possible worlds,” says Dr. Pangloss—again, and again, and again—in Voltaire’s eighteenth-century comic classic Candide. Despite contracting syphilis, losing an eye and an ear, and being enslaved, hanged, and caught in not one but two earthquakes, Pangloss sticks to his story.

Pangloss, of course, was Voltaire’s little joke, poking fun at the silliness of contemporary philosophy, but history has thrown up plenty of real-life versions. The great empires that dominated the Eastern and Western cores in the first few centuries CE seem to have been especially rich in them. “When the emperor makes his imperial tour, all is resplendent,” one Chinese poet wrote. “Boundless joy reigns for ten thousand years.” In the Roman Empire the Greek orator Aristides waxed even more enthusiastic. “For the eternalduration of the empire the whole civilized world prays all together,” he declaimed. “Let all the gods grant that this empire and this city flourish forever and never cease until stones float on the sea and trees cease to put forth shoots.”

So what would these Panglosses have made of Figure 6.1? After peaking around 1 BCE/CE, social development fell in both East and West. This was collapse on a whole new scale. Not only was it broader than ever before, affecting both ends of Eurasia, but it was also longer and deeper. Century after century it dragged on, cutting more than 10 percent off the East’s development score by 400 CE and 20 percent off the West’s by 500. How this happened, ushering in the end of the West’s fourteen-thousand-year-long lead in social development, is this chapter’s subject.


Figure 6.1. An Old World–wide depression: the peak, decline, and fall of the ancient empires, 100 BCE–500 CE


The ancient empires had not always been full of Panglosses. It took hundreds of years of wars and millions of deaths before the paradox of violence that I mentioned in Chapter 5—the fact that war eventually brought peace and prosperity—made itself clear; and no sooner had the wars of unification ended than the Qin and Roman superstates both turned on themselves in horrific civil wars. Qin got down to this immediately; Rome, more gradually.

Qin’s centralized, repressive institutions had been magnificent for conquering but turned out to be less good for ruling. After vanquishing his last enemies in 221 BCE the First Emperor continued conscripting all his male subjects, now setting them to building instead of fighting. Sometimes they were productive, as when they laid thousands of miles of roads and canals; sometimes less so. Sima Qian says that despite convincing himself of his own divinity and spending several fortunes on quacks who promised to make him live forever, the First Emperor—perhaps as insurance—also had 700,000 men spend thirty-six years building his tomb. (The graves of hundreds who died at the site have been excavated.)

The (mostly unexcavated) twenty-square-mile tomb complex is China’s answer to Egypt envy. It is best known today for the Terracotta Army, six-thousand-plus life-size clay soldiers that guarded it, discovered by chance by a work team digging wells in 1974. It is one of the archaeological wonders of the world, but even more astonishing is the fact that when Sima Qian described the First Emperor’s tomb, this Terracotta Army that has astonished museum visitors around the world did not even get a mention. Sima instead saved his words for the tomb’s underground bronze palace, four hundred yards across, surrounded by replicas of the kingdom’s rivers in mercury. (Geochemical surveys in 1981 and 2003 confirmed that the soil above the tomb has massively elevated mercury levels.) All those royal concubines who had not given the First Emperor children, Sima Qian says, plus all the artisans who knew the tomb’s secrets and possibly the empire’s top hundred officials, too, were buried with the emperor in 210 BCE.

The First Emperor’s megalomaniacal policies generated resistance at every level. When noblemen complained, he forcibly moved them to his capital; when intellectuals complained, he buried 460 of them alive; and when peasants complained, he cut them in half.*

The reign of terror imploded almost the moment the First Emperor died. One day in 209 BCE, the story runs, heavy rain prevented two lowly officials from delivering conscripts to a garrison on time. The penalty for lateness was, of course, death. “As things stand, we face death whether we stay or run away,” Sima Qian reports one of them saying, “while if we were to start a revolt we would likewise face death. Since we must die in any case, would it not be better to die fighting for our country [by rebelling]?”

As they anticipated, both rebels were soon killed, but their insurgency spread. Within months, the warring states had reconstituted themselves. By 206 BCE Qin was finished and the revolt became a terrible civil war. After another four years of slaughter only the peasant-turned-warlord Liu Bang remained standing. He proclaimed the Han dynasty, beheaded eighty thousand prisoners of war, announced universal peace, and eventually took the new name Gaodi (“High Emperor”).*

Rome had the opposite problem from Qin. Instead of being too centralized to rule in peace, its institutions were too diffuse. Its senate of rich old men and assemblies of poor citizens had evolved to run a city-state, not an empire, and could not cope with the mountains of plunder, armies of slaves, and gaggle of superrich generals that victory created. In one policy dispute in 133 BCE the august senators smashed up the wooden benches they sat on and used the legs to club one another to death, and by the 80s BCE no one knew for sure who was actually running the empire.

Instead of abruptly collapsing, like Qin, Rome slid in and out of civil war for fifty years. Increasingly armies were loyal to their generals rather than to the state, and the only way the senate could deal with successful generals was by sending them off to attack weaker foreigners (which only made the generals stronger) or by empowering new generals to attack the old ones (which only created new challengers). In 45 BCE Julius Caesar managed to defeat all comers, only to fall to assassins the next year; whereupon the wheel turned again, until in 30 BCE Octavian hunted Antony and Cleopatra down in Egypt, where they committed suicide. Exhausted by constant war, the Roman elite agreed that they would do whatever Octavian (who renamed himself Augustus, “the most august one”) said while pretending he was really just a private citizen. With everyone’s face saved by this odd arrangement, in 27 BCE Augustus declared that the republic had been restored and got down to ruling as an emperor.

By 1 BCE almost the whole of the Eastern and Western cores were under the rule of single empires, but this had not been inevitable. Gaodi, the founder of the Han dynasty, had actually made an agreement to share the Eastern core with his last enemy in 203 BCE, but broke his word, killed his rival, and took everything; and in the 30s BCE it looked as if the Mediterranean would split between a Latin-speaking west, ruled by Octavian from Rome, and a Greek-speaking east, ruled by Antony and Cleopatra from Egypt. Had Gaodi been more honorable, or Antony less addled by liquor and sex, this chapter would have begun differently. In South Asia, things did go differently. Small cities and states developed in the Ganges Valley between 1000 and 600 BCE then shifted toward high-end states like those in the Eastern and Western cores. In the third century BCE these were swallowed into the huge Mauryan Empire, probably the world’s biggest state in its day (though Qin would soon surpass it). But instead of going from strength to strength like Rome and China, this empire gradually broke apart over the next hundred years. By Augustus’ time South Asia was once again home to a mass of jostling little kingdoms.

All happy families resemble one another,” Tolstoy famously said, “but each unhappy family is unhappy in its own way.” So, too, empires. There are countless ways for empires to disintegrate—lost battles, disgruntled governors, uncontrollable grandees, desperate peasants, incompetent bureaucrats—but only one way to stay together: compromise. Han and Roman rulers showed a positive genius for this.

Gaodi won his civil war in 202 BCE only because he cut deals with other warlords, rewarding ten of them by leaving two-thirds of his “empire” as semi-independent kingdoms under their control. To prevent new civil wars, the empire needed to crush these vassal kings, but moving too quickly and scaring them might provoke the very wars the empire needed to prevent—as might moving too slowly and leaving the kings too strong. The Han emperors, however, moved at just the right speed, dismantling the kingdoms by 100 BCE with surprisingly few rebellions.

Han emperors were not as megalomaniacal as the Qin First Emperor, although they had their moments. Jingdi, for instance, was buried in 141 BCE with his own terracotta army (six times as large as the First Emperor’s, though only one-third as tall). But with the partial exception of the great conqueror Wudi, Han emperors backed away from claiming immortality and divinity, though they did hang on to the Shang and Zhou kings’ role as intermediary between this and the supernatural worlds.

They calibrated this carefully. Getting along with the great families required retreating from royal godliness (although the practical step of tying aristocratic wealth to the court’s own success also helped). Placating the gentleman scholars required inserting the throne into an idealized, Confucian model of a hierarchical universe (as well as another pragmatic move, making knowledge of the Confucian classics rather than aristocratic connections the route to administrative office). Maintaining royal authority in the vast countryside required something else again, combining some of the monarchy’s pre–Axial Age status as the bridge to the ancestors and gods with more down-to-earth measures such as reducing military service, relaxing the cruelest Qin laws, and making carefully timed tax cuts.

Compromise created peace and unity, which gradually knit the Eastern core into a single entity. Its rulers called it zhongguo (the “Middle Kingdom” at the center of the world) or tianxia (“All Under Heaven,” because nothing beyond its borders mattered), and at this point it really does start making sense to think of the Eastern core as a single entity that modern Westerners, in their own mispronunciation of “Qin,” call China. Huge cultural differences remained within All Under Heaven, but the Eastern core had started becoming Chinese.

Rome pursued similar compromises. When the civil wars ended in 30 BCE the victorious Augustus demobilized the conscripts and manned the frontier with career soldiers. Like the Han emperors, he knew that the army could threaten his regime, but whereas China’s rulers reacted by staffing their military with convicts and foreigners, in a sense pushing it outside mainstream society, Augustus and his successors decided to keep their enemies even closer than their friends. They made the army a central social institution, but one directly under their own control.

War became the preserve of specialists, and everyone else turned toward the arts of peace. Rome, like China, absorbed its client kings and tied aristocrats’ prosperity to the empire’s. The emperors walked a tightrope, pretending to be merely first among peers when dealing with the aristocracy, commander-in-chief when dealing with the army, and godlike when dealing with parts of the empire that expected their rulers to be numinous. They substituted a god-when-I’m-dead strategy for the old god-for-a-day compromise: emperors were merely outstanding men until they died, the theory held, whereupon they were clutched to the bosoms of the divinities. Some, like the emperor Vespasian, found it ridiculous; as he collapsed, dying, he joked with his courtiers, “I think I’m becoming a god.”

By the first century CE a fusion Greco-Roman culture was developing. Rich men could travel from the Jordan to the Rhine, stopping in similar-looking cities, eating off much the same gold plates, watching familiar Greek tragedies, and making clever allusions to Homer and Virgil, everywhere finding like-minded men who would appreciate their sophistication. The senate admitted more and more provincial worthies, local bigwigs put up inscriptions in Latin and Greek, and even farmers in the fields started thinking of themselves as Romans.

Compromise defused resistance. It would be nice to quote an ancient text on this, but none sums it up quite like the 1979 comedy Monty Python’s Life of Brian. When Reg (played by John Cleese), chairman of the People’s Front of Judea (Official), tries to whip his none-too-zealous followers into an anti-Roman rage, he finds that they prefer talking about the benefits of the empire (especially the wine). Reg throws back at them what has surely become the most famous question ever asked about the Roman Empire: “All right then. Apart from the sanitation, the medicine, education, wine, public order, irrigation, the fresh water system, and public health—what have the Romans ever done for us?” The freedom fighters think for a moment, then one tentatively raises a hand. “Brought peace?” Gasping at this stupidity, Reg answers: “Oh, peace … shut up!”

Reg did not get it: peace changed everything, bringing prosperity to both ends of Eurasia. Population soared in both empires and their economies grew even faster. At the most fundamental level, however we count—total product, product per unit of land, or product per unit of labor—agricultural output rose. Han and Roman laws gave greater security in property to landlords and peasants alike. Farmers at all levels took new land under cultivation, extended irrigation and drainage systems, bought slaves or hired laborers, and used more manure and better tools. Egyptian records show that Roman-era farmers could harvest ten pounds of wheat for every pound sown as seed, a spectacular level for premodern agriculture. No statistics survive from China, but archaeological finds and accounts in agricultural handbooks suggest that yields were high here, too, particularly in the Yellow River basin.

Quietly, so quietly in fact that the noblemen who wrote the surviving literature barely remark on it, farmers and artisans pushed energy capture toward a threshold. Virtually all energy previously used in the entire history of humanity had come from muscles or from biomass fuels, but people now tapped into four potentially revolutionary sources—coal, natural gas, water, and wind.

The first two remained very marginal—a few Chinese blacksmiths used coal in iron foundries, and saltmakers in Sichuan piped natural gas through bamboo tubes and burned it to evaporate brine—but not the third and fourth. In the first century BCE Romans and Chinese both came up with waterwheels, using them to power mills to grind grain and bellows to heat up furnaces. The most impressive example known, built at Barbegal in France soon after 100 CE, linked sixteen wheels to generate thirty kilowatts of power, roughly the same as a hundred oxen (or two Model T Fords running at full speed). Most wheels were much smaller, but even an average Roman mill generated as much power as ten strong men turning wheels with their feet.

The most important use of wind- and waterpower came not from the brand-new waterwheels, though, but from improvements to the older technologies of sailing. No one would bother producing thousands of tons of wheat, millions of gallons of wine, and billions of iron nails unless they could move them from farm or foundry to potential buyers. Bigger, better, and cheaper ships (and harbors and canals) mattered as much as plows and waterwheels. Trade and industry grew together.

Figure 6.2 shows this neatly for the West, plotting the rising number of shipwrecks against levels of lead pollution recorded in a 2005 study of lake deposits at Penido Velho in Spain. (I show shipwrecks because no written records survive of ancient shipping, so—unless captains inexplicably got clumsier and steered onto rocks more often as time went on—shipwrecks are the best proxy for the number of voyages; I show lead pollution, a by-product of silver processing, because lead is the easiest isotope for geochemists to study.) The curves rise together to twin peaks in the first century BCE, showing how strongly trade and industry were linked (and that ancient Rome was no golden age for the environment).


Figure 6.2. Goods and services: the parallel increases in Mediterranean shipwrecks and in lead pollution in the Spanish lake of Penido Velho. Numbers of wrecks and amounts of lead have been normalized so they can be compared on the same vertical scale, with the amounts of each in 1 BCE being counted as 100.

We cannot yet compare Figure 6.2 with an equivalent graph for the East because Chinese archaeologists have not collected much quantifiable data. What there is, though, suggests that trade boomed in the Eastern core after 300 BCE, but not as much as in the Western core. one recent study, for instance, concludes that the Roman Empire had roughly twice as much coinage in circulation as the Han and that the richest Romans were twice as rich as the richest Chinese.

Geography probably had a lot to do with the difference in the growth of trade. In Rome’s empire, 90 percent of the people lived within ten miles of the Mediterranean Sea. In the second millennium BCE the Western core’s expansion into the Mediterranean Basin had brought rising development and increasing disruption in equal measure, but once Rome conquered the entire coastline in the first century BCE it put an end to the disruptions. The sea now allowed cheap water transport to link almost everyone, and development shot up.

In the Han Empire, a much lower proportion of the population lived close to the sea or big rivers, and the rivers were in any case not always navigable. Rome’s military expansion secured a new economic frontier where farmers who applied the most advanced techniques to recently conquered lands could sell their crops to feed the cities of Italy and Greece, but in the absence of waterways like those of the Mediterranean, the Qin and Han conquests did this only on a much smaller scale. Some Han emperors worked furiously to improve transport by dredging the Yellow and Wei rivers and bypassing the worst stretches with canals, but centuries would pass before China solved the problem of not having its own Mediterranean Sea.

Two rather similar forces lay behind economic growth in both East and West, one pulling and one pushing the economy upward. The pull factor was the growth of the state. Roman and Han conquerors taxed vast areas, spending most of their income on armies along the frontiers (probably 350,000 troops in Rome and at least 200,000 in China) and gigantic capital cities (probably a million people at Rome and half that number at Chang’an, the Han capital). Both needed to move food, goods, and money from rich, taxpaying provinces to hungry, revenue-consuming concentrations of humanity.

Monte Testaccio (“Mount Potsherd”), a site in the suburbs of Rome, illustrates the scale of this pull factor in the West. This 150-foot-high, weed-covered mound of broken pottery is less dramatic than the Qin First Emperor’s tomb, but for hard-core archaeologists it is Italy’s answer to Egypt envy. Twenty-five million storage pots, a staggering number, were dumped here across three centuries. Most were used to ship olive oil—200 million gallons of it—from southern Spain to Rome, where urbanites put it on their food, washed with it,* and burned it in their lamps. To stand on Monte Testaccio is to feel awe at what hungry humans can do. And this was just one of Rome’s artificial hills of garbage.

The second force, which pushed the economy upward, was the familiar one of climate change. Global cooling after 800 BCE had thrown low-end states into chaos and set off centuries of expansion. By 200 BCE continuing orbital changes ushered in what climatologists call the Roman Warm Period. This weakened winter winds—bad news for farmers in the Mediterranean and in China’s great river valleys—but the high-end empires that had been created partly in response to the earlier global cooling now gave Eastern and Western societies the resilience not just to survive climate change but also to exploit it. Tougher times increased incentives for diversification and innovation. People tinkered with waterwheels and coal and exploited regional advantages by shipping goods around; high-end states provided roads and harbors to make these profitable and the armies and law codes to make profits secure, on the very sensible assumption that richer subjects will be able to pay more taxes.

High-end empires also pushed beyond the old heartlands into areas where the Warm Period made farming more productive—such as France, Romania, and rainy England in the West, and Manchuria, Korea, and central Asia in the East (Figure 6.3). Without knowing that they were doing it, the empires had effectively hedged their bets, since climate changes that hurt them in the warmer regions helped them in the cooler ones. In Rome, where the Mediterranean made it so easy for traders to move goods between regions, the benefits were surely huge; in China, where the great rivers were less convenient, the benefits must have been smaller, but real all the same.

The payoff from all the wars, enslavements, and massacres of the first millennium BCE was an age of plenty that inspired the Panglossian enthusiasm that opened this chapter. Its fruits were unevenly distributed—there were far more peasants than philosophers or kings—but more people were alive than in any previous age, in bigger cities, and on the whole they lived longer, ate better, and had more things than ever before.

When I began going on archaeological excavations, in 1970s England, I dug on several Roman sites. It could be exhausting work, clearing huge foundations of poured concrete (another Roman invention) with pickaxes and racing to keep the log books one step ahead of the flood of finds. But then I started doing a PhD on Greek society around 700 BCE, and in 1983 dug for the first time on a site of that date. It was a shock. These people just didn’t have anything. Finding even a couple of hunks of rusty iron was a big deal. Compared to earlier populations, Romans lived in a consumer paradise. Per capita consumption in what became the western provinces of the Roman Empire rose from a level near subsistence around 500 BCE to maybe 50 percent above it six or seven hundred years later.


Figure 6.3. Making the most of the weather: the maximum extent of the Han (c. 100 CE) and Roman (117 CE) empires, incorporating areas that benefited from global warming

Similar processes were clearly under way in the East, too, even if, as I mentioned earlier, they are not yet so well quantified. People in both cores remained desperately poor by modern standards—half of all babies died before their fifth birthday, few people lived past fifty, and poor diets typically left adults six inches shorter than us—but compared to all that had gone before, this was a golden age. Small wonder the ancient empires were crawling with Dr. Panglosses.


What the Panglosses could not see, though, was how surging social development within the cores was also transforming the worlds beyond the empires’ borders. When empires were strong, they imposed their wills on the peoples along their frontiers, as when Darius of Persia in the sixth century BCE and the Qin First Emperor in the third brought great swaths of the central Asian steppe under their control; but when empires were weak, the nomads pushed back. In the West, the successor states that Alexander the Great’s generals built on the ruins of the Persian Empire after 300 BCE could never match the might of their illustrious predecessor, and Scythian raiders were soon plundering Bactria and northern India. Another central Asian group, the Parthians, began infiltrating Iran; and when the Macedonian kingdoms fell apart under the weight of Roman attacks after 200 BCE, the Parthians took full advantage.

The Parthians differed from earlier nomads who had pushed their way into the Western core. Nomads such as the Scythians got rich by robbing or extorting protection money from agrarian empires; they were basically bandits, with no interest in conquering high-end states and managing their bewildering bureaucracies. The Parthian horsemen, by contrast, were only seminomads. They came from the edges of the central Asian steppe rather than its barren heart, and had been living alongside farmers for generations. Their rulers knew how to extract taxes from downtrodden peasants while maintaining the horseback traditions that their military power depended on; and by about 140 BCE they had turned much of the old Persian Empire into a loosely integrated kingdom of their own.

The Parthian monarchs liked to call themselves the heirs of Cyrus and Darius and strenuously assimilated themselves to Western high culture, but in reality theirs was always a low-end state. It could never threaten Rome’s existence, although it did administer a short, sharp shock to any Roman who forgot the power of nomadic cavalry. Parthia’s horsemen were famous for the “Parthian shot,” where a rider pretended to flee, then turned in his saddle to loose arrows at his pursuer. Tactics such as these allowed Parthia to see off the Roman general Crassus, who lost his army and his life in a rash attack in 53 BCE. The Parthian king, a great admirer of Western culture, was watching a Greek tragedy when Crassus’ head was brought to him; his education was good enough that he could get the joke when the lead actor worked the grisly memento into his lines.

Rome’s problems with Parthia at the western end of the steppes, however, paled by comparison with China’s with the Xiongnu at the eastern end. There the Qin First Emperor’s preemptive war in 215 BCE had disastrous results: instead of intimidating the nomads, it set off a political revolution on the steppes, fusing the feuding Xiongnu tribes into the world’s first true nomad empire. Rather than taxing peasants to pay for a mounted aristocracy, like the Parthians did, the Xiongnu overlord Maodun funded his ultra-low-end state entirely by plundering China and buying the loyalty of lesser nomad chiefs with captured silk and wine.

Maodun’s timing was excellent. He took over the Xiongnu in 209 BCE, right after the First Emperor’s death, and for nine years exploited China’s civil wars to loot to his heart’s content. In 200 BCE the first Han emperor, Gaodi, decided that enough was enough, and led a huge army into the steppe, only to learn that fighting nomads was different from fighting rivals for China’s throne. The Xiongnu fell back, letting the Chinese starve in the wilderness, and by the time Maodun turned and sprang an ambush, one-third of Gaodi’s men had lost fingers to frostbite. The Chinese emperor barely got out in one piece; and as generally happens in war, most of his men fared worse.

When he realized that attrition, inaction, and preemption were all failing against the Xiongnu, Gaodi came up with a fourth strategy: he would make Maodun family. Tearing his eldest daughter from Chang’an’s polished stone chambers and pearl-seeded bedspreads,* Gaodi packed her off to be Maodun’s wife, to count out her days in a felt tent on the steppe. A thousand years later Chinese poets still sang of the heartbreak of the Han maiden alone among the fierce horsemen.

This royal marriage initiated what Chinese scholars euphemistically called the harmonious kinship policy, and just in case love was not enough, Gaodi also bought Maodun off with annual “gifts” of gold and silk. Unfortunately the gifts did not really work either. The Xiongnu kept raising the price and then plundering anyway, confident that so long as the costs of the damage were less than the costs of going to war to punish them, Han emperors would do nothing.

Harmonious kinship lasted for sixty increasingly expensive years, until in the 130s BCE the Han court split bitterly over it. Some remembered the disaster of 200 BCE and urged patience; others bayed for blood. In 135 BCE, when his cautious mother died, the young Emperor Wudi joined the sanguinary crowd. Each year from 129 through 119 BCE he sent armies hundreds of thousands strong into the wilderness, and each year barely half their number returned. The cost in lives and treasure was appalling, and Wudi’s critics—the educated elite who wrote the history books—concluded that his preemptive war had been a disaster.

But Wudi’s campaigns, like those Darius of Persia waged against the Scythians four hundred years earlier (which were also judged a failure by the history writers), transformed the nomad problem. Deprived of gifts and plunder to share with subordinates and with their grazing lands under constant threat, Xiongnu rulers lost control of their allies and started fighting one another. In 51 BCE they acknowledged Han rule, and about a century later broke into two tribes. One retreated northward; the other settled inside the Chinese empire.

By the first century CE the Romans and Han had both gained the initiative against the nomads. The Han started “using barbarians to fight barbarians,” as they called it, giving the Southern Xiongnu a place to live (and constant “gifts”) in return for military service against other nomads. Rome, protected by the forests, mountains, and farms of eastern Europe from most movements along the steppe highway, only directly faced (semi)nomads in Parthia; and even here, Rome faced them not on the steppe, where nomads had so many advantages, but among the cities and canals of Mesopotamia. Whenever emperors got serious, Rome’s legions brushed Parthian resistance aside.

That said, neither Rome’s eastern nor China’s northern frontier ever entirely settled down. In 114 CE Rome chased the Parthians out of Mesopotamia, getting control of the whole Western core, only to abandon the land between the rivers in 117. Four more times in the second century Rome overran Mesopotamia, and four more times gave it up. Despite its wealth, Mesopotamia was just too far away and too difficult to hold. China, by contrast, found that bringing the Xiongnu inside its territory gradually converted its border from a line on a map into a fluid frontier zone, a Wild North where people came and went as they liked, the government’s writ rarely ran, and a good sword mattered more than legal niceties.

The growing entanglements of the nomadic and agrarian empires were altering Eurasia’s geography, shrinking the world just a little. The most visible consequence is a huge zone of shared material culture, stretching from Ukraine to Mongolia, through which merchants and warriors passed Eastern and Western ideas, art, and weapons from hand to hand. The most important cargoes moving between East and West, though, were ones that no one could see at all.

In the thousands of years since Old World farmers had started crowding into villages, they had evolved a nasty set of pathogens. Most were highly contagious; many could be fatal. Large populations breathing on one another and sharing body fluids spread diseases rapidly, but sheer numbers also meant that plenty of people happened to have the right antibodies to resist them. Over the millennia these people spread their defenses through the gene pool. Random mutations could still turn dormant diseases back into killers that would burn through the human population like wildfire, but hosts and viruses would then work out a new balance where both could survive.

People exposed for the first time to an unfamiliar package of germs have few defenses against the silent killers. The most famous example is what the geographer and historian Alfred Crosby has called the “Columbian Exchange,” the horrific, unintended fallout of Europe’s conquest of the New World since 1492 CE. Entirely separate disease pools had evolved in Europe and the Americas. America had unpleasant ailments of its own, such as syphilis, but the small, rather thinly spread American populations could not begin to compete with Europe’s rich repertoire of microbes. The colonized peoples were epidemiological virgins. Everything from measles and meningitis to smallpox and typhus—and plenty in between—invaded their bodies when the Europeans arrived, rupturing their cells and killing them in foul ways. No one knows for sure how many died, but the Columbian Exchange probably cut short the lives of at least three out of every four people in the New World. “It appears visibly that God wishes that [the natives]yield their place to new peoples,” one sixteenth-century Frenchman concluded.

A similar but more evenly balanced “Old World Exchange” seems to have begun in the second century CE. The Western, South Asian, and Eastern cores had each evolved their own unique combination of deadly diseases in the thousands of years since agriculture had begun, and until 200 BCE these developed almost as if they were on different planets. But as more and more merchants and nomads moved along the chains linking the cores, the disease pools began to merge, setting loose horrors for everyone.

Chinese documents record that mysterious pestilences broke out in an army fighting nomads on the northwest frontier in 161–162 CE, killing a third of the troops. In 165 ancient texts again talk of disease in the army camps; but this time the texts are Roman, describing pestilence in military bases in Syria during a campaign against Parthia, four thousand miles from the Chinese outbreak. Plagues returned to China five more times between 171 and 185 and ravaged the Roman Empire almost as often in those years. In Egypt, where detailed records survive, epidemics apparently killed more than a quarter of the population.

It is hard to figure out just what ancient diseases were, partly because viruses have continued to evolve in the past two thousand years, but mostly because ancient authors described them in such maddeningly vague ways. Just as aspiring writers today can buy books such as Screenwriting for Dummies then churn out movies or TV shows to formula, ancient authors knew that any good history needed politics, battles, and plagues. Their readers, like us when we go to movies, had a strong sense of what these plot elements should look like. Plagues needed omens of their approach, gruesome symptoms, and staggering death tolls; rotting corpses, the breakdown of law and order, and heartbroken widows, parents, and/or children.

The easiest way to write a plague scene was to lift it from another historian and just change the names. In the West the archetype was Thucydides’ eyewitness account of a plague that hit Athens in 430 BCE. In 2006, a DNA study suggested that this was a form of typhoid fever, though that is not entirely obvious from Thucydides’ narrative; and after other historians had recycled his (admittedly gripping) prose for a thousand years, not very much at all is obvious about the epidemics they described.

Despite this fog of uncertainty, Roman and Chinese sources contrast sharply with Indian literature, which mentions no plagues in the second century CE. That may just reflect the educated classes’ lack of interest in something as mundane as the deaths of millions of poor people, but more likely the plagues really did bypass India, which suggests that the Old World Exchange spread mostly across the Silk Road and steppes rather than by the Indian Ocean trade routes. That would certainly be consistent with how the epidemics began in China and Rome, in army camps on the frontiers.

Whatever the mechanisms of microbial exchange, terrible epidemics recurred every generation or so from the 180s CE on. In the West the worst years were 251–266, when for a while five thousand people died each day in the city of Rome. In the East the darkest days came between 310 and 322, beginning again in the northwest, where (according to reports) almost everyone died. A doctor who lived through the sickness made it sound like measles or smallpox:

Recently there have been persons suffering from epidemic sores that attack the head, face, and trunk. In a short time, these sores spread all over the body. They have the appearance of hot boils containing some white matter. While some of these pustules are drying up a fresh crop appears. If not treated early the patients usually die. Those who recover are disfigured by purplish scars.

The Old World Exchange had devastating consequences. Cities shrank, trade declined, tax revenues fell, and fields were abandoned. And as if all this were not enough, every source of evidence—peat bogs, lake sediments, ice cores, tree rings, strontium-to-calcium ratios in coral reefs, even the chemistry of algae—suggests that the weather, too, turned against humanity, ending the Roman Warm Period. Average temperatures fell about 2°F between 200 and 500 CE, and since the cooler summers of what climatologists call the Dark Age Cold Period reduced evaporation from the oceans and weakened the monsoon winds, rainfall declined as well.

Under other circumstances, the flourishing Eastern and Western cores might have responded to climate change just as effectively as they had done when the Roman Warm Period began in the second century BCE. But this time disease and climate change—two of the five horsemen of the apocalypse who featured so prominently in Chapter 4—were riding together. What that would mean, and whether the other three horsemen of famine, migration, and state failure would join them, would depend on how people reacted.


Like all organizations, the Han and Roman empires had evolved to solve specific problems. They had learned how to defeat all rivals, govern vast territories and huge populations with simple technologies, and move food and revenue from rich provinces to the armies on their frontiers and the crowds in their great cities. Each, though, did all this in slightly different ways, and the differences determined how they responded to the Old World Exchange.

Most important was how each empire dealt with its army. To confront the Xiongnu from the 120s BCE onward, the Han had developed huge cavalry squadrons, increasingly recruited from the nomads themselves, and as they perfected the “using barbarians to fight barbarians” policy in the first century CE they settled many of these nomads within the empire. This had the double consequence of militarizing the frontier, where Xiongnu fighters lived with little Han supervision, and demilitarizing the interior. Few troops were to be found in the heart of China, except at the capital itself, and fewer still were recruited there. Chinese aristocrats saw little to gain from serving as officers over “barbarians” stationed far from the capital. War became something that distant foreigners did on the emperor’s behalf.

The upside for emperors was that they no longer had to worry that powerful noblemen would use the army against them; the downside, that they no longer had much of a stick with which to beat any noblemen who did become troublesome. Consequently, as the state’s monopoly on force weakened, aristocrats found it easier to bully local peasants, swallowing their farms into huge estates that the landlords ran as private fiefdoms. There is a limit to how much surplus can be squeezed out of peasants, and when the landlord was so near and the emperor so far away, more surplus was handed over to local masters as rent and less sent to Chang’an as tax.

Emperors pushed back, limiting the size of estates aristocrats could hold and the number of peasants on them, redistributing land to free (and taxable) small farmers, and raising cash from state monopolies on necessities such as iron, salt, and alcohol. But in 9 CEthe emperor-landlord tussle turned critical when a high official named Wang Mang seized the throne, nationalized all land, abolished slavery and serfdom, and pronounced that from now on only the state could own gold. His near-Maoist centralization collapsed immediately, but peasant uprisings convulsed the empire, and by the time order returned, in the 30s CE, Han policy had gone through a sea change.

The emperor who replaced Wang Mang, Guangwu (reigned 25–57 CE), came from a propertied family, not one that drew its power from links to the old court. To restore Han authority, Guangwu had to work closely with his fellow magnates, and he threw his lot in with them, initiating a golden age for landowners. Growing as rich as kings and ruling thousands of peasants, these grandees virtually ignored the state and its bothersome taxmen. Formerly Han emperors had moved troublesome landowners to Chang’an so they could keep an eye on them, but Guangwu instead moved the capital to Luoyang (Figure 6.4), where the landowners were strongest and the magnates could monitor the court.*

The elite began rolling back the state and steadily disengaging from its biggest budget item, the army. By the late first century CE, with the Xiongnu no longer a major threat, the great cavalry army that had been built to fight them was being left to fend for itself, which meant plundering the peasants it supposedly protected. By about 150 CE the Southern Xiongnu, theoretically vassals, were more or less independent.

Nor was much effort made to reshape the army to meet new threats being posed by the Qiang, a name the Chinese used loosely for farmers and herders around their western frontier. Thanks perhaps to the clement weather of the Roman Warm Period, Qiang numbers had been growing for generations and small groups had moved into the western provinces, occupying land when they could, fighting and stealing when they could not. To keep this under control the frontier needed garrison troops, not nomadic cavalry, but the landowners of the Luoyang region did not want to pay for them.


Figure 6.4. The end of the Han dynasty, 25–220 CE: locations mentioned in the text

Some officials suggested abandoning the western provinces altogether and leaving the Qiang to their own devices, but others feared a domino effect. “If you lose Liang province,” one courtier argued, “then the Three Adjuncts will be your border. If the people of the Three Adjuncts move inward, then Hongnong will be the border. If the people of Hongnong move inward, then Luoyang will be the border. If you carry on like this you will reach the edge of the Eastern Sea, and that, too, will be your border.”

Persuaded, the government stayed the course and spent a fortune, but infiltration continued. In 94 and again in 108 CE Qiang groups took over broad swaths of the western provinces. In 110 there was a general Qiang uprising, and by 150 the Qiang were as much beyond Luoyang’s control as were the Xiongnu. On both the western and the northern frontiers local landowners had to organize their own defenses, turning dependent peasants into militias, and the governors, forgotten by the state that had sent them there, also raised their own armies (and plundered their provinces to pay them).

It must have been hard not to conclude that the Han had lost the mandate of heaven, and in 145 CE three separate rebellions demanded a new dynasty. For the great landowning elite, however, the cloud had a thick silver lining. The empire was smaller, tax receipts were dwindling, and the army was, in a sense, being privatized, but their estates were more productive than ever, imperial tax collectors left them alone, and war was but a distant rumor. All was, after all, for the best.

China’s Panglosses had a rude awakening when the Old World Exchange burst onto this scene in the 160s. Plagues ravaged the northwest, where the Qiang were moving into the empire, and spread across the land. And rather than responding with strong leadership, the imperial court imploded.

In theory, the hundreds of bureaucrats who filled offices at the palace in Luoyang lived only to put the emperors’ wishes into practice, but in practice (like civil servants in many eras) they had their own interests too. Most came from landowning families, and tended to be remarkably good at finding reasons not to do things that landowners found distasteful (like raising money for wars). Any emperor with ideas of his own had to work around them. Some emperors brought in kinsmen, particularly relatives of their multiple wives, to get things done; others turned to eunuchs, whose advantages I mentioned in Chapter 5. Astute emperors used both to great effect, but these agents, too, had their own agendas, and tried to make sure that emperors were not astute. In fact, they so arranged matters that after 88 CE no prince over the age of fourteen ever survived to ascend the throne. Court politics degenerated into backstairs intrigues among senior ministers, eunuchs, and boy emperors’ in-laws.

In 168 CE, at the very moment Han China most needed leadership, palace eunuchs staged a coup against the in-laws of the newly installed twelve-year-old emperor, Lingdi. For almost twenty years, while epidemics raged and Xiongnu and Qiang raided, the court launched purge and counterpurge, claiming thousands of lives and paralyzing government. Corruption and incompetence reached new heights. Injustice sparked uprisings, and, unable to muster or command armies, Lingdi’s handlers authorized local strongmen to raise troops and do what they thought necessary.

People cried out for explanations of this abrupt descent into chaos, and when neither Confucian rituals nor Daoist mysticism provided them, self-proclaimed visionaries filled the gap. In the Yellow River valley a physician won a great following by teaching that sin caused disease and that confession brought health. In the 170s he went one step further: the dynasty itself, he concluded, was the ultimate source of sin and contagion. It had to go. “When a new cycle of sixty years begins,” he pronounced, “great fortune will come to the world.”

But great fortune did not come. Instead, when the new calendar cycle began on April 3, 184, things got even worse. Even though pro-Han armies suppressed the rebels (known as Yellow Turbans from their headgear, yellow being the symbol of the new age), imitators popped up all over China. Heaven itself seemed to be showing its displeasure when the Yellow River flooded massively, displacing 365,000 peasants. A “Five Pecks of Grain” movement (promising freedom from sickness to those who confessed their sins and paid five measures of rice) turned Sichuan into an independent Daoist theocracy; the Qiang exploited the chaos and plundered western China again; the special commanders deputized to contain these threats made themselves independent warlords; and when the court did act, it only made things worse.

In 189 Lingdi recalled the mightiest warlord, Dong Zhuo, but Dong wrote back saying, “The Han and barbarian troops under my command all came to me and said … ‘Our provisions will be cut off, and our wives and children will die of hunger and cold.’ Pulling back my carriage, they would not let me go.” When Lingdi insisted, Dong called his bluff, returning to Luoyang but bringing his army with him. Lingdi conveniently died as Dong approached, and the courtiers around Lingdi’s senior widow (who backed a thirteen-year-old as the new ruler) and the eunuchs (who backed an eight-year-old) set about murdering one another. Dong broke into Luoyang, massacred the eunuchs, murdered the older boy, and set up the younger as Emperor Xiandi. Then he torched Luoyang and wondered what to do next.

The Han were no longer in control, but neither was Dong, because while the emperors’ managerial, high-end power had failed, their vaguely divine, low-end power persisted. No one dared proclaim himself emperor while Xiandi lived, but no one dared murder the boy king either. (Warlords, however, were fair game; Dong was assassinated in 192.) As the power brokers squabbled, using Emperor Xiandi as a pawn, the empire broke down into fiefdoms, the Xiongnu and Qiang took over the frontiers, and the high-end institutions that had seemed so solid melted into air.

My armor has been worn so long that lice breed in it,” the warlord and part-time poet Cao Cao wrote sometime after 197.

Myriad lineages have perished,

White bones exposed in the fields,

For a thousand
li [roughly three hundred miles] not even a cock is heard.

Only one out of a hundred survives.

Thinking of it rends my entrails.

Cao contained his grief long enough, however, to snatch Xiandi and manipulate the boy emperor into making him the main player in northern China.

Cao was a complicated man. He may well have been trying to restore the Han dynasty, casting himself in the time-honored role of wise adviser. Seeing how landlords had undermined the old high-end state, he tried to solve the military problem by settling his soldiers in colonies where some grew food while others trained for war, and the political problem by classifying the gentry into nine ranks, determining their positions in a meritocracy. Like Tiglath-Pileser in Assyria a thousand years earlier, he was cutting the magnates out of the picture, and until 208, when his navy was wiped out at the battle of the Red Cliffs, it looked as if Cao might pull China together again.

Yet despite these efforts, Cao (thanks largely to an enormous fourteenth-century novel called The Romance of the Three Kingdoms) has been remembered chiefly as the monster who destroyed the Han. In twentieth-century Peking Opera, actors wearing the Cao mask with its caked white makeup and black-lined eyes were always the villain audiences loved to hate, and in the 1990s Cao went high-tech, jumping to the computer screen as the bad guy in countless video games. He made it to bigger screens as the villain of a TV version of The Romance (in eighty-four episodes), and to the biggest screens of all in the costliest Asian-financed film ever made (The Battle of the Red Cliffs, costing $80 million; Part One was released to coincide with the 2008 Beijing Olympics).

Cao’s bad reputation has more to do with what happened after his death than with his own misdeeds. After the battle of the Red Cliffs a balance developed among three main warlords, and after 220, when Cao’s son finally told Emperor Xiandi to abdicate, the country devolved into three kingdoms. The one that Cao founded, though, was always the strongest. It crushed one of its rivals in 264, rebranded itself as the Jin dynasty,* and in 280 raised a huge army and fleet that finished reconquering China.

For the next decade, the post-Han collapse looked like a brief aberration, comparable perhaps to what had happened in the Western core after 2200 or 1750 BCE, when climate change, migrations, and famine caused state collapse but had little impact on social development. But it soon turned out that the fall of the Han was in fact much more like the Western collapse around 1200 BCE, with enormous long-term consequences.

Battlefield victories could reduce the number of surviving warlords to one but could not change China’s underlying problems. The aristocracy remained as strong as ever and rapidly undermined Cao’s military colonies and meritocracy. Epidemics still raged, and the Dark Age Cold Period was making life harder not only for farmers in the Yellow River valley but also for the Xiongnu and Qiang. Between 265 and 287 a quarter of a million central Asians settled inside the Jin Empire. Sometimes the Jin welcomed the manpower they provided; at other times the authorities simply could not stand up to them.

In this context, little things such as an emperor’s love life could assume huge importance. Rather carelessly, the Jin emperor sired twenty-seven sons, and when he died in 289 some of them hired the wildest nomads they could find to fight one another. The nomads, no fools, quickly realized that they did not have to settle for the wages they were paid: they could demand any price they liked. When a Xiongnu chief did not get his price in 304, he turned up the heat by announcing that he was founding a new kingdom. The Jin still did not give him everything he wanted, so his son burned Luoyang in 311, desecrated the Jin dynasty’s family tombs, and took its emperor prisoner, setting him to serve wine at feasts. Still not getting the loot they thought they deserved, in 316 the Xiongnu destroyed Chang’an, too, and captured the new Jin emperor, putting this prisoner in charge of washing cups as well as serving wine. Tiring of the game after a few months, the Xiongnu killed him and his relatives.

The Jin state collapsed. Bands of Xiongnu and Qiang plundered at will across north China, and the Jin court, with a million followers in its train, fled to Jiankang (modern Nanjing) on the Yangzi River. The northern lands they gave up were home to some of the world’s most advanced agriculture, but under the combined impact of high death rates (as epidemics hit home) and high emigration, much now reverted to the wild. That suited the nomads who moved in from the steppes just fine, but for remaining farming communities it meant that famine also reared its head. In happier days, local gentry or the state might have stepped in with aid, but now there was no one to help. To make the misery complete, plagues of locusts devoured what surpluses the villagers still produced. New epidemics, perhaps carried by migrants from the steppes, brought yet more woes to the weakened population. Smallpox probably made its first appearance in China in 317, the year after Chang’an burned.

The wars that Xiongnu and Qiang chiefs waged across this barren landscape were more like giant slave raids than clashes between high-end states. Rulers rounded up peasants, tens of thousands at a time, and herded them into territories around new capital cities, where the bondsmen tilled fields to feed armies of full-time cavalrymen. The horsemen, meanwhile, imported new weapons from the steppes—proper saddles, stirrups, and bigger horses that could charge while wearing armor and carrying armored knights—that made infantry virtually obsolete. Those Chinese aristocrats who did not flee south took to the hills, their dependent peasants crowding into huge stockades that offered the only refuge from marauding horsemen.

The new states forming in north China (“The Sixteen Kingdoms of the Five Barbarians,” as Chinese historians contemptuously called them) were highly unstable. In 350, for instance, one state imploded in an orgy of ethnic cleansing, with native Chinese slaughtering Inner Asians. “The dead numbered more than two hundred thousand,” the official dynastic history says. “Corpses were piled outside the city walls, where they were all eaten by jackals, wolves, and wild dogs.” Other chiefs swarmed into the power vacuum this left. By 383 one lord briefly looked like he might unite all China; but as he closed in on Jiankang, an apparently minor defeat mutated into a panic-stricken rout, and by 385 his entire state had ceased to exist.

Refugees fleeing south from the destruction of Chang’an founded an “Eastern Jin”* state at Jiankang in 317. Unlike the bandit kingdoms in northern China, this boasted a luxurious, sophisticated court and kept up the appearances of how Chinese royalty should live. It sent ambassadors to Japan and Indochina, produced magnificent literature and art, and, most remarkable of all, survived for a century.

But behind the surface glitter, the Eastern Jin kingdom was as bitterly divided as any northern state. The former northern grandees who fled south had little interest in obeying the emperor’s commands. Some refugee noblemen clustered in Jiankang, becoming parasitic timeservers and feeding off the royal court; others colonized the Yangzi Basin and carved out estates in this hot, wet new homeland. They drove off indigenous peoples, felled forests, drained swamps, and settled refugee peasants as serfs.

Conflict was endemic at every level. The new noblemen who had fled from the north feuded with older southern families; aristocrats of all stripes struggled against middling magnates; the rich and the middling elites both squeezed the peasantry; Chinese of all classes pushed natives back into the mountains and forests; and everyone resisted the embattled court at Jiankang. Despite all their heartbroken poetry about the lost lands of the north, the landlords of southern China were in no hurry to pay the taxes or surrender the powers that might have allowed a reconquest. The mandate of heaven had been lost.


Unlike the crisis of the twelfth century BCE, the crisis triggered by the Old World Exchange was Eurasia-wide, and its Western component inspired what was arguably the first masterpiece of modern historical writing, Edward Gibbon’s History of the Decline and Fall of the Roman Empire. His subject, Gibbon declared, was an “awful revolution,” one “which will ever be remembered, and is still [in the 1770s] felt by the nations of the earth.” He was right: only during his lifetime had Western social development regained the dizzy heights it had reached under the Roman Empire.

The early Roman and Han emperors had faced similar problems but had tried different solutions. Terrified of civil war, Chinese rulers neutralized the army, but then had few weapons against powerful landlords; Roman rulers instead took over the army, putting relatives in command and filling its ranks with citizens. This made it harder for civilians to defy emperors, but easier for soldiers to do so.

It took skill to manage this system, and since plenty of Rome’s rulers were unhinged, periodic crashes were unavoidable. Caligula’s orgies and decision to make his horse a consul were bad enough, but Nero’s fondness for forcing senators to sing in public and murdering anyone who annoyed him was too much. In 68 CE three different factions in the army proclaimed their own generals as emperor and it took a brutal civil war to sort matters out. “Now was revealed,” the historian Tacitus noted, “the secret of empire—that emperors could be made outside Rome.” Wherever there were soldiers, there could be a new emperor.

The Roman solution did, however, preserve the frontiers (Figure 6.5). The Germans beyond the Rhine and Danube, like the Qiang along China’s western border, experienced population growth in the first centuries CE. They responded by fighting one another, trading with Roman towns, and slipping across the rivers into the empire. For all these activities, organizing into larger groups with stronger kings made sense. Like the Han, Rome responded to increasingly porous borders by building walls (most famously Hadrian’s across Britain), monitoring trade, and fighting back.


Figure 6.5. Rome’s third-century crisis. The dotted areas show where Germanic, Gothic, and Persian raids were common.

In 161 CE, when Marcus Aurelius Antoninus became emperor, Rome still seemed to be in sturdy health, and Marcus looked forward to following his passion—philosophy. Instead, he had to confront the Old World Exchange. The first serious epidemic broke out in army camps on China’s northwest frontier the year he ascended the throne, and the very same year a Parthian invasion of Syria forced Marcus to concentrate troops there. Their crowded camps provided the ideal host for disease to spread, and in 165 a pestilence (smallpox? measles? the literary accounts are, as ever, vague) devastated them. It reached Rome in 167, just as population movements far to the north and east were pushing new, powerful Germanic federations across the Danube. Marcus spent the rest of his life—thirteen years—fighting them.*

Unlike China, Rome won its second-century frontier wars. Had it not, Rome—like the Han—might have lurched into crisis in the 180s. As it was, though, Marcus’ victories affected only the pace of change, not its results, which suggests that armies alone could not halt the collapse. The epidemics’ massive death toll had thrown the economy into chaos. Food prices and agricultural wages soared, which made the plagues a boon for the farmers who survived, who could abandon less-productive fields and concentrate on the best land; but as farming contracted and taxes and rents fell, the larger economy went into free fall. The number of shipwrecks in the Mediterranean declines sharply after 200, and pollution in ice cores, lake sediments, and bogs follows after 250 (Figure 6.6). By then everyone was feeling the pinch. Bones from cattle, pigs, and sheep become smaller and scarcer in settlements after 200, suggesting declining standards of living, and by the 220s wealthy city dwellers were putting up fewer grand buildings and inscriptions.


Figure 6.6. Declining and falling: numbers of Mediterranean shipwrecks and levels of lead pollution in the lake bed at Penido Velho, Spain, across the first millennium CE. The downward slopes mirror the upward slopes in the first millennium BCE shown inFigure 6.2. As in Figure 6.2, numbers of wrecks and amounts of lead have been normalized so they can be compared on the same vertical scale, with the amounts of each in 1 CE being counted as 100.

Fifty years after Marcus’ victories, Rome lost control of its frontiers anyway. Just as victories over the Xiongnu in the first century BCE had paradoxically made it harder for the Han to control their borders, a string of Roman successes undermined Parthia so badly that the regime collapsed before a Persian uprising in the 220s CE. The new Sassanid dynasty that emerged forged a much stronger army and in 244 defeated a Roman force and killed the emperor who led it.

Rushing troops and money to prop up the collapsing eastern front left Rome unable to defend its Danube and Rhine frontiers properly. Instead of sneaking across in little gangs to steal cattle, war bands hundreds or thousands strong now pushed through the denuded lines, burning, looting, and carrying off slaves. The Goths, who had only recently migrated to the Balkans from the shores of the Baltic, raided as far as Greece and in 251 defeated and killed another Roman emperor. By then more epidemics had broken out, perhaps carried by these population movements. When Rome finally mustered another army against Persia, in 259, it hit a new low: the emperor Valerian was captured and thrown in a cage, where he remained for a year, dressed in slave’s rags and suffering ingeniously horrible torments. Romans insisted that Valerian’s fortitude impressed his captors, but the reality seems to be that the Persians, like the Xiongnu when they captured Chinese emperors, eventually got bored. They flayed Valerian and hung his skin on their capital’s walls.

The Old World Exchange and the rise of Sassanid Persia transformed Rome’s position. At the very moment that population was falling and the economy stumbling, emperors needed more money and troops than ever before. Their first (not-so-bright) idea, paying for new armies with debased currency, simply made money worthless and accelerated economic collapse. Appalled by the failures of central government, armies took matters into their own hands, proclaiming new emperors with bewildering speed. In contrast to earlier emperors, these men had no whiff of divinity about them at all. Most were tough soldiers, and some were illiterate privates. Few lasted longer than two years, and all died by the sword.

With army factions spending more time fighting one another than defending the provinces, local grandees followed the same path as their Chinese counterparts, turning the peasants into dependents and organizing them into militias. The Syrian trading city of Palmyra managed to throw the Persians back, theoretically on Rome’s behalf, but its warrior queen Zenobia (who led her troops in person and regularly attended city assemblies dressed in armor) then turned on Rome too, overrunning Egypt and Anatolia. At the other end of the empire a governor on the Rhine declared an independent “Kingdom of the Gauls,” taking Gaul (modern France), Britain, and Spain with him.

By 270 Rome looked rather like China had done in 220, divided into three kingdoms. But despite all the turmoil, Rome’s situation was actually less dire. By taking on Persia and the Germans in the 260s, Palmyra and Gaul bought the empire a breathing space, and the cities around the Mediterranean—the empire’s fiscal backbone—remained largely secure. So long as goods kept moving by sea, money kept coming into the imperial coffers, and the new, hardheaded military men who sat on the throne could recover and rebuild. Trading the philosophers’ beards and flowing locks of earlier emperors for shaved chins and crew cuts, they hiked taxes in the regions they still controlled, built a strike force around armored cavalry, then turned on their enemies. They smashed Palmyra in 272, Gaul in 274, and most of the Germanic war bands by 282. In 297 Rome even got some revenge for Valerian by capturing the Persian royal harem.

The emperor Diocletian (reigned 284–305) exploited this turnaround with administrative, fiscal, and defensive reforms that adapted the empire to deal with the new world. The army more or less doubled in size. The frontiers never entirely settled down, but Rome was now winning more battles than it lost, blunting Germanic raids with defense in depth and wearing the Persians down in sieges. To handle all this activity Diocletian split his job into four parts, with one ruler and a deputy handling the western provinces and another ruler and deputy the eastern. Predictably, the empire’s multiple rulers fought two-, three-, or four-way civil wars as often as they fought external enemies, but compared to the twenty-seven-way civil war in China’s Jin Empire in the 290s, this was stability indeed.

A new empire was taking shape. Rome itself ceased to be a capital city, as decision-making shifted in the western provinces to forward bases near the frontiers and in the eastern to a grand new city at Constantinople. But in the end, no amount of reorganization could solve the empire’s underlying problems. The economic integration built up over so many centuries had been shaken. The eastern provinces revived in the fourth century, with trade in grain, wine, and olive oil again spreading wealth far down the hierarchy, but the western provinces steadily drifted out of this circuit. Great landlords in western Europe held on to much of the power they had gained during the third century, tying “their” peasants to the land and shielding them from state taxation. As estates grew more self-sufficient, the cities around them dwindled and trade and industry declined further still; and the toughest problems were simply beyond any emperor’s ken. Temperatures and rainfall kept declining, whatever rulers said or did; epidemics kept killing; and peoples on the steppe kept moving.

Sometime around 350, a group called the Huns moved west across Kazakhstan, sending dominos tumbling in every direction (Figure 6.7). Just why they inspired such fear is debated. Ancient writers blamed their sheer horribleness; modern scholars more often point to the powerful bows they used. Once again, we can only observe the consequences. Nomads fleeing the Huns broke into India and Iran or retreated west into modern Hungary. That made life difficult for the Goths, who had settled as farmers in what we now call Romania after their third-century raids on the empire. After heated internal debates, the Goths asked Rome for sanctuary inside the empire.

There was nothing new in this. Rome had developed a policy rather like the Han “using barbarians to fight barbarians,” routinely admitting immigrants, dividing them into small groups, then enrolling them in the army, settling them on farms, or selling them as slaves. This simultaneously relieved pressure on the frontiers, raised troop numbers, and increased the taxable population. The immigrants, naturally, often had different ideas, preferring to settle as a group inside the empire and continue living as they had before. To prevent this, Rome needed always to have enough troops on hand to overawe the immigrants.

The Goths’ arrival at the Danube in summer 376 was a tough call for Emperor Valens, who ruled the eastern provinces from Constantinople. On the one hand, there were too many Goths for comfort. On the other, the potential gains from accepting so many immigrants were enormous, and it might in any case be difficult to keep them out, especially since Valens’ best troops were away fighting Persia. He decided to admit the Goths, but almost as soon as they crossed the river his commanders on the ground, more interested in profiteering than in dispersing the immigrants, lost control. Half-starved Goths broke out, looting what is now Bulgaria and demanding a homeland within the empire. Playing hardball, Valens refused to negotiate. He disentangled his army from the Persian front and rushed back to the Balkans—only to make another bad decision, giving battle rather than waiting for his western co-emperor to bring more help.


Figure 6.7. Scourges of God: the coming of the Huns and the collapse of the western Roman Empire, 376–476 CE. The map shows three major groups of invaders (Huns, solid lines; Goths, broken lines; Vandals, dotted lines) with the dates of their main movements. There were countless smaller migrations too.

About fifteen thousand Romans (many of them Germanic immigrants) fought maybe twenty thousand Goths at Adrianople in August 378. Two-thirds of the Romans, including Valens, died in the rout that followed. Back in Augustus’ day, losing ten thousand troops would barely have registered; Rome would have called up more legions and taken terrible revenge. By 378, though, the empire was stretched so thin that these men could not be replaced. The Goths were inside the empire and out of control.

A peculiar standoff developed. The Goths were not nomads like the Xiongnu, stealing things and then riding off to the steppes, nor were they imperialists like the Persians, come to annex provinces. They wanted to carve out their own enclave in the empire. But with no siege engines to storm cities and no administration to run them, they needed Roman cooperation; and when that was not forthcoming they rattled around the Balkans, trying to blackmail Constantinople into granting them their own kingdom. Lacking legions to expel them, the eastern emperor pleaded poverty, bribed the Goths, and skirmished with them, until, in 401, he persuaded them that they would get a better deal by migrating westward, whereupon they became his co-emperor’s problem.

But all this clever diplomacy ceased to matter in 405 when the Huns resumed their western progress. More dominos fell and more Germanic tribes pressed against Rome’s frontiers. The legions, now chiefly made up of Germanic immigrants and led by a half-German general, wore them down in bloody campaigns, and diplomats wove yet more webs, but on New Year’s Eve, 406, Rome finally lost control when thousands of Germans poured across the frozen Rhine. There were no more armies to stop them. The immigrants fanned out, taking everything. The poet Sidonius, among the richest of the rich, described the indignities he had to endure when a band moved onto his estate in Gaul. “Why ask for a song to Venus,” he wrote to a correspondent living back in Rome, “when I’m stuck in the middle of a long-haired rabble, forced to listen to Germanic speech, keeping a straight face while I praise songs from a swinish Burgundian who spreads rancid butter in his hair? … You don’t have the stink of garlic and onions from ten breakfasts belched on you early every morning.” Plenty would have envied Sidonius, though. Another eyewitness put things more bluntly: “All Gaul is filled with the smoke of a single funeral pyre.”

The army in Britain rebelled, taking charge of its own defense, and in 407 what remained of the Rhine armies joined it. By then everything was falling apart. Struggling to get the western Roman emperor’s attention amid so many disasters, the Goths invaded Italy in 408 and in 410 sacked Rome itself. They finally got their deal in 416, with the emperor agreeing that if the Goths helped him drive the Germans and assorted usurpers out of Gaul and Spain, they could keep part of the territory.

Rome’s frontiers, like China’s, had become places where barbarians (as each empire called outsiders) settled and then took imperial pay to defend the empire against more barbarians trying to push their way in. It was a lose-lose situation for the emperors. When the Germanic Goths (now fighting on Rome’s side) defeated the Germanic Vandals (fighting against Rome) in Spain in 429, the Vandals crossed to North Africa. It may seem hard to believe, but what is today the Tunisian Sahara Desert was then Rome’s breadbasket, ten thousand square miles of irrigated fields, exporting half a million tons of grain to Italy each year. Without this food, the city of Rome would starve; without the taxes on it, Rome could not pay its own Germans to fight enemy Germans.

For another ten years brilliant Roman generals and diplomats (themselves often of German stock) managed to keep the Vandals in check and parts of Gaul and Spain loyal, but in 439 it all came crashing down. The Vandals overran Carthage’s agricultural hinterland and Rome’s worst-case scenario abruptly materialized.

Rulers in Constantinople were often quite happy to see their potential rivals in Rome struggling, but the prospect of the western parts of the empire actually breaking up alarmed the eastern emperor Theodosius II enough that he mustered a large force to help liberate what is now Tunisia. But as his troops gathered in 441, yet another blow fell. A new king of the Huns, Attila—the “Scourge of God,” as Roman authors called him—erupted into the Balkans, leading not just ferocious cavalry but also a modern siege train. (Refugees from Constantinople may have brought him this technology; an ambassador from Theodosius described meeting such an exile at Attila’s court in 449.)

As his cities crumbled under the Huns’ battering rams, Theodosius canceled the attack on the Vandals. He saved Constantinople—just—but these were dark days for Rome. The city still had perhaps 800,000 residents around 400 CE; by 450 three-quarters had left. Tax revenues dried up and the army evaporated, and the worse things got, the more usurpers tried to seize the throne. Attila chose this moment to decide he had squeezed the Balkans dry, and turned west. The half-Gothic commander of Rome’s western armies managed to convince the Goths that Attila was their enemy too, and, leading an almost entirely Germanic force, he dealt Attila the only defeat of his career. Attila died before he could get revenge. Bursting a blood vessel during a drinking bout to celebrate his umpteenth wedding, the Scourge of God went to meet his maker.

Without Attila the loose Hun Empire disintegrated, leaving the emperors in Constantinople free to try to put the western empire back together again, but not until 467 did all the requirements—money, ships, and a Roman strongman worth backing—fall into place. Emptying his treasury, the eastern emperor sent his admiral Basiliskos with a thousand ships to recapture North Africa and heal the western provinces’ fiscal backbone.

In the end, the fate of the empire came down to the wind. In summer 468, as Basiliskos closed on Carthage, the breezes should have been blowing westward along North Africa’s shore, pushing Basiliskos’ ships along. But at the last moment the wind shifted and trapped them against the coast. The Vandals sent burning hulks into the packed Roman vessels, just the tactics that the English would use against the Spanish Armada in 1588. Ancient ships, with their tinder-dry ropes, wooden decks, and cloth sails, could turn into infernos in seconds. Piled on top of one another, panicking to push the fireships away with poles, and with no room to escape, the Romans lost all order. The Vandals came in for the kill, and it was all over.

In Chapter 5 I talked about the great-man theory of history, which holds that it is unique geniuses, such as Tiglath-Pileser of Assyria, not grand impersonal forces, such as the Old World Exchange, that shape events. The other side of the great-man coin is the bungling-idiot theory of history: What, we have to ask, would have happened had Basiliskos had the wits not to get trapped against the coast?* He probably would have retaken Carthage, but would that have restored the Italy–North Africa fiscal axis? Maybe; the Vandals had been in Africa for less than forty years, and the Roman Empire might have been able to rebuild economic structures quickly. Or then again, maybe not. Odoacer, king of the Goths, the strongest strongman in western Europe, already had his eye on Italy. In 476 he wrote to Zeno, the emperor in Constantinople, observing that the world no longer needed two emperors. Zeno’s glory was sufficient for everyone, Odoacer said, and he made a proposal: he would run Italy—loyally, of course—on Zeno’s behalf. Zeno understood full well that Odoacer was really announcing his takeover of Italy, but also knew it was no longer worth arguing about.

And so the end of Rome came, not with a bang but a whimper. Would Zeno have been any better placed to defend Italy if Basiliskos had recovered Carthage than he actually was in 476? I doubt it. By this point preserving a Mediterranean-wide empire was beyond anyone’s power, and the fifth century’s frenzied maneuvering, politicking, and killing could do little to change the realities of economic decline, political breakdown, and migrations. The classical world was finished.


The Eastern and Western cores had each split in two. In China, the Eastern Jin dynasty ruled the southern part of the old empire, but saw themselves as rightful heirs to the whole realm. Similarly, in the West a Byzantine Empire (so called because its capital, Constantinople, stood on the site of the earlier Greek city Byzantium) ruled the eastern part of the old Roman Empire but claimed its entirety (Figure 6.8).

The Eastern Jin and Byzantine Empires remained high-end states, with bureaucrats, taxes, and salaried armies. Each boasted great cities and learned scholars, and the farms of the Nile and Yangzi valleys were richer than ever. But neither compared with the Roman and Han empires in their heydays. Their worlds were shrinking as northern China and western Europe slid out of the cores.

Disease, migration, and war had dissolved the networks of managers, merchants, and money that had bound each of the earlier empires into a coherent whole. The new kings of fourth-century northern China and fifth-century western Europe were determinedly low-end, feasting with their long-haired warrior lords in the grand halls they had captured. These kings were happy to take taxes from conquered peasants, but without salaried armies to pay, they did not absolutely need this revenue. They were already rich; they were certainly strong; and trying to manage bureaucracies and extract regular taxes from their unruly followers often seemed more trouble than it was worth.



Figure 6.8. The divided East and West: (a) the Eastern Jin and China’s major immigrant kingdoms, around 400 CE; (b) Byzantium and Europe’s major immigrant kingdoms, around 500 CE

Many of the old, rich aristocratic families of northern China and the western Roman Empire fled to Jiankang or Constantinople with their treasures, but even more stayed amid the ruins of the old empires, perhaps holding their noses like Sidonius, and made what deals they could with their new masters. They swapped their silk robes for woolen pants, their classical poetry for hunting, and assimilated to the new realities.

Some of those realities turned out to be quite good. The superrich aristocrats of former times, with estates scattered over the whole Han or Roman Empire, disappeared, but even with their properties restricted to a single kingdom, some fourth-and fifth-century landowners remained staggeringly wealthy. The old Roman and Chinese elites intermarried with their conquerors, and moved from the crumbling cities to great manors in the countryside.

As the drift toward low-end states accelerated in the fourth century in northern China and the fifth in western Europe, kings allowed their noblemen to seize as rent the surpluses that peasants had formerly handed over to the taxman. If anything, these surpluses might have been growing as population fell and farmers could concentrate their efforts on the best lands. Countryfolk had lost few of the skills they had learned across the centuries and had indeed added new ones. Drainage techniques in the Yangzi Valley and irrigation in the Nile Valley improved after 300; ox-drawn plows multiplied in northern China; and seed drills, moldboard plows, and watermills spread across western Europe.

But despite all the nobles’ ostentation and the peasants’ ingenuity, the steady thinning of the ranks of bureaucrats, merchants, and managers who had prospered so mightily under the Han and Roman empires meant that the larger economies kept on shrinking at both ends of Eurasia. These characters had often been venal and incompetent, but they really had performed a service: by moving goods around they capitalized on different regions’ advantages, and without these go-betweens, economies grew more localized and more oriented toward subsistence.

Trade routes contracted and cities shrank. Southern visitors were shocked by the decay of cities in northern China, and in some parts of the old Roman Empire the decline was so sharp that poets wondered whether the great stone ruins decaying all around them could have been built by mortals at all. “Snapped rooftrees, towers tottering, the work of Giants,” reads an English verse of around 700 CE. “Rime [mold] scours gatetowers, rime on mortar; shattered are shower shields, roofs ruined. Age underate them.”

In the first century CE the emperor Augustus had boasted that he had turned Rome from a city of brick to one of marble, but by the fifth century Europe reverted to a world of wood, with simple shacks thrown up in open spaces between the crumbling shells of old Roman town houses. Nowadays we know quite a lot about these humble homes, but when I started going on digs in England in the 1970s, excavators were still struggling to develop techniques careful enough to recover any traces of them at all.

In this simpler world, coinage, counting, and writing lost their uses. With no one mining copper to supply their mints, the kings of northern China first tried reducing the metal content of their coins (to the point, some claimed, that the coins were so light they could float) and then stopped issuing coins altogether. Account-keeping and census-taking shriveled up and libraries rotted. It was an uneven process, and drawn out across centuries, but in most of northern China and western Europe population fell, thistles and forests reclaimed fields, and life grew shorter and meaner.


How could this have happened? To most Easterners and Westerners, the answer was obvious: the old ways and old gods had failed.

In China, as soon as the frontiers crumbled, critics had accused the Han of losing the mandate of heaven, millenarian healing cults had convulsed the land, and the most creative minds within the educated elite had begun questioning Confucian certainties. The “Seven Sages of the Bamboo Grove,” a group of third-century freethinkers, became icons of a new sensibility, reportedly passing their days in conversation, poetry, music, drinking, and drugs rather than studying the classics and serving the state. According to one story, the sage Ruan Ji, caught in a scandalous breach of etiquette (walking unchaperoned with his sister-in-law), just laughed: “Surely you do not mean to suggest that li”—custom, the foundation of Confucianism—“applies to me?” He expanded on his theme:

Have you ever seen the lice that inhabit a pair of pants? They jump into the depths of the seams, hiding themselves in the cotton wadding, and believe they have a pleasant place to live. Walking, they do not risk going beyond the edge of the seam; moving, they are careful not to emerge from the pants leg; and they think they have kept to the rules of etiquette. But when the pants are ironed, the flames invade the hills … then the lice that inhabit the pants cannot escape.

What difference is there between the gentleman who lives within a narrow world and the lice that inhabit pants legs?

The moral seriousness of Han court poets now appeared ludicrous; far better, said the new generation, to withdraw into pastoral, writing lyrical descriptions of gardens and forests, or even to become a hermit. Aesthetes who were too busy to retreat to the distant mountains might just play at being hermits in the gardens of their own villas, or—like Wang Dao, chief minister at the court in Jiankang around 300—could hire people to be hermits on their behalf. Painters began celebrating wild mountains, and in the fourth century the great Gu Kaizhi raised landscape to the status of a major art form. The Seven Sages and other theorists elevated form over content, studying the techniques of painting and writing rather than their moral message.

This third-century revolt against tradition was largely negative, mocking and rejecting convention without offering positive alternatives, but toward the century’s end that changed. Eight hundred years earlier, while Confucianism and Daoism were just getting started in China, Buddhism had also been spreading across South Asia. The Old World Exchange brought Buddhism to Chinese attention, probably when Eastern and South Asian traders mingled in central Asia’s oases, and it is first mentioned in a Chinese text in 65 CE. A few cosmopolitan intellectuals took it up, but it long remained just one among many exotic philosophies washing in from the steppes.

That changed in the late third century, thanks largely to the central Asian monk-translator Dharmaraksa. Traveling regularly between Chang’an and the great oasis of Dunhuang, he attracted Chinese intellectuals with new translations of Buddhist texts, putting Indian concepts into language that made sense in China. Like most Axial sages, the Buddha had written nothing down, which left endless scope for debate over what his message was. The earliest forms of Buddhism had emphasized disciplined meditation and self-awareness, but the interpretation that Dharmaraksa promoted, known as Mahayana Buddhism, made salvation less onerous. Dharmaraksa presented the Buddha not as a spiritual seeker but as the incarnation of an eternal principle of enlightenment. The original Buddha, Dharmaraksa insisted, was just the first in a series of Buddhas on this and other worlds. These Buddhas were surrounded by a host of other heavenly figures, particularly Bodhisattvas, mortals who were well on the way to enlightenment but had postponed nirvana to help lesser mortals perfect themselves and escape the cycle of rebirth and suffering.

Mahayana Buddhism could get extreme. Most Buddhist sects believed that a Maitreya (“Future”) Buddha would one day lead the masses to liberation, but starting in 401 a stream of wilder-eyed Chinese devotees identified themselves as Buddhas and, teaming up with bandits, rebellious peasants, and/or disaffected officials, went on rampages intended to bring salvation to everyone right now. All ended bloodily.

Mahayana Buddhism’s most important contribution, though, was to simplify traditional Buddhism’s burdensome demands and open salvation to all. By the sixth century all that the popular “Heaven-Man Teaching” required was for devotees to walk laps around statues of the Buddhas and Bodhisattvas, worship relics (especially the many teeth, bones, and begging bowls said to have belonged to the Buddha), chant, act compassionately, be self-sacrificing, and follow the Five Precepts (thou shalt not kill, steal, commit adultery, drink, or lie). Its teachers conceded that this would not actually lead to nirvana, but it would deliver health, prosperity, and upwardly mobile rebirth. The “Pure Land School” went further, claiming that when believers died, the Bodhisattva of Compassion, working with the Amitabha Buddha, would interrupt the cycle of rebirth and guide them to a Western Paradise where they could pursue nirvana away from the cares of this world.

Indian seekers after nirvana regularly took to the road, begging as they went. Holy wanderers (as opposed to well-heeled hermit-poets) were alien to Chinese traditions, and did not catch on, but a second Indian path toward enlightenment—monasticism—did. Around 365, Dao’an—a native Chinese Buddhist trained as a Confucian, rather than a central Asian immigrant—drew up a monastic code to fit Chinese society. Monks would wear the tonsure and both monks and nuns took vows of chastity and obedience, earning their keep through labor while pursuing salvation through prayer, meditation, and scholarship. Monasticism could get as extreme as millenarian Buddhism: many monks and nuns injured themselves, imitating—in a small way—the Bodhisattvas’ self-sacrifice, and a few even burned themselves alive, sometimes before audiences of thousands, to redeem others’ sins. Dao’an’s great contribution, though, was to shape monasticism into a religious institution that could partly fill the organizational void created in China by the breakdown of state institutions in the fourth century. Monasteries and convents built watermills, raised money, and even organized defense. As well as being centers of devotion they became oases of stability and even islands of wealth as rich co-religionists gave them land and tenants and dispossessed peasants fled to their protection. Thousands of monasteries popped up in the fifth century; “Today,” an official wrote in 509, “there is no place without a monastery.”

Buddhism’s conquest of China was remarkable. There could have been only a few hundred Buddhists in 65 CE; by the sixth century most Chinese—perhaps 30 million people—were believers. Yet astonishing as this is, at the other end of Eurasia another new religion, Christianity, was growing even faster.

Classical traditions did not crumble as early in the West as in the East, perhaps because Rome’s frontiers held longer, and although Western healing cults did arise after the great epidemics of the 160s, they did not favor the kinds of violent revolution popular among Chinese versions. Yet the chaos of the third century did unsettle old ways in the West. Statues carved all over the empire bear silent witness to a new mood, abandoning the stately principles of classical art in favor of strangely proportioned forms with huge, upward-staring eyes, seemingly gazing on another, better place. New religions from the empire’s eastern margins—Isis from Egypt, the Undefeated Sun from Syria, Mithras (whose followers wallowed in bulls’ blood in underground chambers) perhaps ultimately from Iran, Christianity from Palestine—offered eternal life. People were asking for salvation from this troubled world, not rational explanation of it.

Some philosophers responded to the crisis of values by trying to show that the scholarship of past centuries was still relevant. In their day, scholars such as Porphyry and Plotinus (the latter perhaps the greatest Western thinker since Aristotle) who reinterpreted the Platonic tradition to fit modern times were among the biggest names in the West, but increasingly thinkers were looking for entirely new answers.

Christianity offered something for everyone in this troubled age. Like Mahayana Buddhism, it was a new twist on an old Axial Age idea, offering a version of Axial thought more in tune with the needs of the day. Christianity took over Judaism’s sacred books, announcing that its founder, Jesus, was the Messiah predicted there. We might call both Mahayana Buddhism and Christianity “second-wave” Axial religions, offering new kinds of salvation to more people than their first-wave predecessors and making the path toward salvation easier. Equally important, both new religions were ecumenical. Neither Jesus nor the Buddha belonged to a chosen people; they had come to save everyone.

Jesus, like the Buddha, wrote no sacred texts, and as early as the 50s CE the apostle Paul (who never met Jesus) was struggling to get Christians to agree on a few core points about what Christianity actually was. Most followers accepted that they should be baptized, pray to God, renounce other gods, eat together on Sundays, and perform good works, but beyond these basic premises, almost anything was possible. Some held that the God of the Hebrew Bible was merely the last (and lowest) in a series of prior gods. Others thought the world was evil and so God the Creator must be wicked too. Or maybe there were two gods, a malevolent Jewish one and Jesus’ wholly good (but unknowable) father. Or two Jesuses, a spiritual one who escaped crucifixion and a bodily one who died on the cross. Maybe Jesus was a woman, some suggested, and maybe women were equal to men. Maybe new revelations could overrule the old ones. Maybe Jesus’ Second Coming was imminent, in which case no Christian should have sex; maybe its imminence meant Christians should practice free love; or maybe only people who were martyred in horrible ways would go to heaven, in which case sex was irrelevant.

The Buddha was widely believed to have been pragmatic about transcendence, recommending that people use whichever of his ideas helped and ignore the rest. Multiple paths to nirvana were not a problem. For Christians, however, getting into heaven depended on knowing who God and Jesus were and doing what they wanted, and so the chaos of interpretations forced believers into a frenzy of self-definition. In the late second century most came to agree that there should be bishops who would be treated as descendants of the original apostles with the authority to judge what Jesus meant. Preachers with wilder ideas were damned into oblivion, the New Testament crystallized, and the window on revelations closed. No one could tinker with the Good Book and no one could hear from the Holy Spirit unless the bishops said so; and no one had to renounce marital sex or be martyred, unless they wanted to.

Plenty of points of disputation remained, but by 200 Christianity was becoming a disciplined faith with (reasonably) clear rules about salvation. Like Mahayana Buddhism, it was distinctive enough to get attention, offering practical paths to salvation in troubled times, yet familiar enough to be comprehensible. Learned Greeks even suggested that second-wave Axial Christianity was not so different from first-wave Axial philosophy after all: Plato (the Athenian Moses, some called him) had reasoned his way to the truth and Christians had had truth revealed to them, but it was all the same truth.

When high-end state institutions started breaking down, bishops were well placed to step into the gap, mobilizing their followers to rebuild town walls, fix roads, and negotiate with Germanic raiders. In the countryside conspicuously holy men, renouncing the world as vigorously as any Buddhist, became local leaders. One ascetic achieved empire-wide fame by living in a tomb in the Egyptian desert, fasting, and battling Satan, all the while wearing a hair shirt. His greatest promoter insisted, “He neither bathed his body with water to free himself from filth, nor did he ever wash his feet.” Another holy man sat on a fifty-foot column in Syria for forty years, while other renouncers wore animal skins and ate only grass, living (briefly, presumably) as “fools for Christ.”

All this struck fastidious Roman gentlemen as bizarre, and even Christians worried about wild men who inspired fanatical followings and answered to no one but God. In 320 an Egyptian holy man named Pachomius found a solution, herding local hermits into the first Christian monastery, where they pursued salvation through labor and prayer under his rigid discipline. Pachomius and the Chinese Dao’an surely knew nothing of each other, but their monasteries were strikingly alike and had similar social consequences. In the fifth century Christian monasteries and convents often moored local economies when larger structures broke down, became centers of learning as classical scholarship waned, and provided monkish militias to keep the peace.

Christianity spread even faster than Buddhism. When Jesus died, around 32 CE, he had a few hundred followers; by 391, when Emperor Theodosius declared Christianity the only legal religion, more than 30 million Romans had converted, although “conversion” is necessarily a loose word. While some highly educated men and women were going through torments of doubt, working through the doctrinal implications with great logic and rigor before accepting the new faith, all around them crowds thousands strong could be won over by Christian or Buddhist wonder-workers in a single afternoon. Consequently, all statistics remain crude; we are doing chainsaw art again. We simply do not know, and probably never will, exactly when and where the pace of conversion accelerated and when and where it slackened, but since we know that both Christianity and Buddhism started with a few hundred followers and eventually had 30-million-plus, Figure 6.9 shows what the average growth rates for each religion must have been across these centuries, smoothed out over the whole of China and the Roman Empire. On average, Chinese Buddhism was growing by 2.3 percent each year, meaning that it doubled its following every thirty years, but Christianity grew by 3.4 percent, doubling every twenty years.

The lines in Figure 6.9 march up, while those for social development in Figure 6.1 fall steadily down. The obvious question—is there a connection?—already recommended itself to Edward Gibbon back in 1781. “We may hear without surprise or scandal,” he observed, “that the introduction … of Christianity, had some influence on the decline and fall of the Roman empire”—but the influence, Gibbon held, was not of the kind that Christians themselves liked to believe. Rather, he suggested, Christianity sapped the empire’s vigor:

The clergy successfully preached the doctrines of patience and pusillanimity; the active virtues of society were discouraged; and the last remains of military spirit were buried in the cloister: a large portion of public and private wealth was consecrated to the specious demands of charity and devotion; and the soldiers’ pay was lavished on the useless multitude of both sexes, who could only plead the merits of abstinence and chastity.


Figure 6.9. Counting souls: the growth of Christianity and Chinese Buddhism, assuming constant rates of change. The vertical scale is logarithmic, as in Figures 3.6 and 3.7, so the constant average rates of growth (3.4 percent per annum for Christianity, 2.3 percent for Buddhism) produce straight lines.

Patience and pusillanimity were as much Buddhist virtues as Christian; so might we extend Gibbon’s argument and conclude that ideas—the triumph of priestcraft over politics, revelation over reason—ended the classical world, driving down social development century after century and also narrowing the gap between East and West?

The question cannot be shrugged off lightly, but I think the answer is no. Like first-wave Axial thought, the second-wave Axial religions were more the consequence than the cause of changes in social development. Judaism, Greek philosophy, Confucianism, Daoism, Buddhism, and Jainism all emerged between 600 and 300 BCE, when social development pushed past the level (roughly twenty-four points) at which the Western core had collapsed around 1200 BCE. They were responses to high-end states’ reorganization and disenchantment of the world. Second-wave Axial religion was a mirror image of this: as the Old World Exchange destabilized high-end states, people found first-wave thought wanting and salvation religions filled the gap.

Unless the averaged-out growth rates in Figure 6.9 are wildly off the mark, Christianity and Chinese Buddhism were marginal before the Old World Exchange. By 250, though, there were about a million Christians (roughly one Roman in forty), which was apparently some kind of tipping point. Christianity now started seriously annoying the emperors; not only was it competing for revenues in one of Rome’s darkest hours, but its jealous God also ruled out the god-when-I’m-dead compromise that had helped rulers justify their power for so long. The emperor Decius began major persecutions in 250, just before the Goths killed him. In 257 Valerian started another pogrom, only for the Persians to kill him, too.

Despite these discouraging examples and the obvious fact that using force to intimidate people whose highest goal was to die as horribly as Jesus was bound to be a losing proposition, emperors tried on and off for another fifty years to wipe Christianity out. But with congregations growing on average by 3.4 percent each year, the miracle of compound interest took church membership to around 10 million members, a quarter of the empire’s population, in the 310s. That was apparently a second tipping point: in 312, in the middle of a civil war, the emperor Constantine found God. Instead of trying to squelch Christianity, Constantine worked out a new compromise, just as his predecessors half a millennium earlier had worked out compromises with the equally subversive first-wave Axial thought. Constantine transferred massive wealth to the church, made it tax-exempt, and recognized its hierarchy. In return the church recognized Constantine.

Over the next eighty years the rest of the population turned Christian, aristocrats colonized the church’s leadership, and the church and state between them plundered the empire’s pagan temples—perhaps the biggest redistribution of wealth the world had yet seen. Christianity was an idea whose time had come. The king of Armenia turned Christian in the 310s, as did Ethiopia’s ruler in the 340s. Persia’s kings did not, but that was probably because Iranian Zoroastrianism was evolving along similar lines to Christianity anyway.

Chinese Buddhism seems to have passed through rather similar tipping points. In Figure 6.9 it hits the million-member mark around 400, but because conditions were so very different in northern and southern China, the growth of the faith had different consequences in each region. In the unsettled north, Buddhists tended to cluster for safety in the capital cities, which made them very vulnerable to royal pressure. By 400 Northern Wei, the strongest of the kingdoms, had set up a government department to supervise Buddhists, and in 446 it started persecuting them. In southern China, by contrast, instead of concentrating in the capital at Jiankang, Buddhist monks scattered down the Yangzi Valley, where they could get powerful aristocrats to protect them against the court and could force emperors to make concessions. In 402 an emperor even accepted that monks should not have to bow in his presence.

Figure 6.9 suggests that there may have been 10 million Buddhists in China by 500, and when the new faith reached this second tipping point, rulers (in northern China as well as southern) made the same decision as Constantine and lavished wealth, tax exemptions, and honors on the flock’s leaders. In the south the genuinely pious emperor Wudi supported vast Buddhist festivals, banned animal sacrifice (people had to consume pastry imitations instead), and sent envoys to India to gather sacred texts. In return, the Buddhist hierarchy recognized Wudi as a Bodhisattva, the redeemer and savior of his people. The kings of Northern Wei got an even better deal, asserting the right to pick their own chief monks and then having the monks pronounce that the kings were reincarnations of the Buddha. Constantine would have been jealous.

Patience and pusillanimity did not cause the decline and fall of East or West. The paradox of social development did that. To some extent the declines and falls followed the script written in the West around 1200 BCE, when the expanding core set off chains of events that no one could control, but to some extent the sheer scale of social development by 160 CE rewrote the script, transforming geography by linking East and West together across central Asia and creating an Old World Exchange of microbes and migrants.

By 160 CE the empires of the classical world were much bigger and stronger than the kingdoms of the Western core had been in 1200 BCE, but so, too, were the disruptions that their primitive version of globalization set off. The classical empires could not cope with the forces they unleashed. Century after century, social development slid. Writing, cities, taxes, and bureaucrats lost their value, and as the old certainties stopped making sense, a hundred million people sought salvation from a world gone wrong by giving new twists to ancient wisdom. Like first-wave Axial thought, second-wave ideas were dangerous, challenging the authority of husbands over wives, rich over poor, and kings over subjects, but once again the mighty made their peace with the subversive, redistributing power and wealth in the process. By 500 CE states were weaker and churches stronger, but life went on.

If I had been writing this book around the year 500 CE I might well have been a long-term lock-in theorist. Every millennium or so, I would have observed, social development undermined itself, and for every two or three steps forward there would be one step back. Disruptions were getting bigger, now affecting the East as well as the West, but the pattern was clear. During steps forward, the West pulled away from the East; during steps back, the gap narrowed; and on it would go, in a series of waves, each cresting higher than the last one, with the West’s lead varying but locked in.

But if I had been writing a century later, things would have looked entirely different.

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