An urge to tell foreigners how to live their lives while getting rich from their labours has long been a characteristic of the west. "You say that it is your custom to burn widows," the British general Sir Charles Napier is reported to have told a group of Hindus who were on the point of consigning a woman to a pyre. "Very well - we also have a custom. When men burn a woman alive, we tie a rope around their necks and hang them." Good, robust stuff. And maybe those concerned today with saving the women of Afghanistan from patriarchal bullying might, in their most secret fantasies, imagine themselves addressing the Taliban in similarly forthright terms.
It was not, however, as a campaigner for gender equality that Napier served in India. Rather, what ended up winning him his Order of the Bath and a statue in Trafalgar Square was his achievement in conquering Sindh, a region so fabulously wealthy that the East India Company had long dreamed of little else but getting it in its clutches. Napier, like the British empire that he served, gave with one hand but took away with the other. Good news for widows; less so for anyone obliged to cough up taxes to the Raj.
Not that the west has been alone in this. Perhaps it is the very definition of a successful civilisation that it should balance an aptitude for violence with a deep inner conviction that its morals are superior to those of everyone else. The Persians and the Romans, the Chinese and the Arabs: all of them blazed this trail. Where the west has been exceptional, however, is that both its greed and its ethical presumptions have been so destabilising to other civilisations that they have served to transform the entire world. For centuries, the face of globalisation was European; even now, with Europe itself in eclipse and the United States in relative decline, this seems unlikely to change. So deeply embedded in western presumptions are the structures that govern world affairs, from diplomacy to finance, from technology to the law, that it would take a truly prodigious effort to reset them on new foundations. Those who do dream of making the attempt, whether in the back rooms of the United Nations or in the badlands of Pakistan, largely lack the power to impose their will. Those who might have the power also tend to have other priorities. The Chinese, for instance, unlike the Americans, appear to have little interest in exporting their way of life around the world. As dramatic as the shift in the balance of power between east and west may be, it seems unlikely that Confucius will ever come to wield the influence in Washington that Marx and Adam Smith have done in Beijing.
All of which is testament to how deeply shaped by history we remain, even in the hyper-globalised world of the 21st century. In the heyday of the Middle Kingdom, after all, it was generally held as a mark of weakness, not potency, to take an interest in the slough of backwardness that lurked beyond China's borders. Emperors best displayed their greatness by keeping the glories of their civilisation to themselves. Despite the voyages of exploration that were sponsored by the Ming during the 15th century, and which at one stage had a fleet of junks cruising off the Horn of Africa, these expeditions were never a priority. The imperial authorities, it appears, felt that barbarians so far distant from themselves should be left to lead their savage and uninteresting lives as they pleased. Coming, as they did, from the richest and smuggest country in the world, the Chinese were simply not hungry enough for what other lands had to offer.
Meanwhile, towards the end of the same century, ships were starting to appear in the Indian Ocean adorned with crosses and carrying crews positively ravening after loot. The Portuguese and Spaniards combined missionary zeal with a lust for gold that was bred largely of poverty. The blend of moral self-confidence and brutality they brought to the Pacific sea lanes, and then to the Americas, was to prove lethally effective. The west was still three centuries and more from global dominance during the lifetimes of Vasco da Gama and Christopher Columbus, but the pattern that would extend to every point of the compass was already being set. Missionaries and gold mines; quinine and Gatling guns; NGOs and cluster bombs: the changes since have been less of kind than of degree.
I was thinking about some of these things this summer on a visit to Mexico City. It was there that I looked at a portrait of the first ever victim of European expansion overseas to become well known back in Europe. In 1519, Moctezuma II, king of the people whom we remember as the Aztecs, but who should more properly be known as the Mexica, ordered that a huge likeness of himself be sculpted in the bedrock of his summer palace. Not much remains: only a leg and the faded traces of a body's outline. When it was finished, however, it showed the Mexican monarch as a guarantor of seasonal renewal, confirming to his people that spring was bound to return after the barrenness of winter. In fact, the year of its completion brought a less welcome arrival - that of a band of heavily armed Spanish explorers on Mexican shores.
As the exhibition at the British Museum makes clear, the empire that Moctezuma ruled was a civilisation no less distinctive and sophisticated than any of the others elsewhere on the globe destined to find themselves alternately looted and lectured by western powers. What added to the primal quality of Moctezuma's encounter with Hernán Cortés, the leader of the pale-faced invaders, was that the Mexica, unlike the peoples of Eurasia and much of Africa, had never suspected that other continents might so much as exist. Moctezuma himself thought that the invading Spaniards might be gods. It was this fatal incomprehension that served to doom both him and the civilisation he had believed it was his divinely appointed task to protect - thereby confirming the conquerors' assurance that it was they who had God on their side.
“Who could conquer Tenochtitlán?" demanded a Mexica poem in praise of the empire's capital. "Who could shake the foundation of heaven?" That an outlaw, in effect, such as Cortés, in command of barely 500 adventurers, should have made himself the master of a metropolis so vast that it was four times the size of Seville, the largest city in contemporary Spain, and immeasurably richer, is still a source of amazement.
Here, in the sheer drama and implausibility of the Spanish conquest, was an archetype of adventure that the west would never forget. It would give to subsequent notions of Manifest Destiny and la mission civilisatrice a breathless, Boy's Own quality, bred of the presumption that a handful of westerners were always bound to prove a match for the natives, no matter how teeming or bloodthirsty they might be. Nor has its glamour wholly faded today, when tales of empire-building tend to leave us embarrassed rather than inspired. One can see Cortés as a distant source of inspiration for the Pentagon officials who planned the lightning strike on Baghdad, as well as the wider adventurer tradition that gave us Tintin and Captain Kirk. It may not be too fanciful to perceive a touch of the conquistador spirit still in the projected mission to Mars.
The other side of such expeditions, however, has often been the bringing of ruin and death to those lucky enough to have been "discovered" or "liberated". Even as they gloried in the fabulous scale of their achievement, Cortés and his followers were not oblivious to its horrendous cost. "An enchanted vision" - this was how Tenochtitlán had appeared to one conquistador as he approached it for the first time. "It was all so wonderful that I do not know how to describe this glimpse of things never heard of, seen or dreamed of before."
Yet the city's glories ended up obliterated, its temples levelled, the beautiful lake in which it sat filled with rubble, and its inhabitants slaughtered. "We could not but be saddened," Cortés later reflected, "by their determination to die." Ultimately, it was not the Spaniards themselves, but rather the germs that they brought with them, which truly spelled disaster for the Mexica, and for all the native peoples of America. Millions upon millions died. The survivors faced exploitation and poverty, and the demographic make-up of the New World was for ever altered. Such was the world's first taste of what globalisation might bring.
No wonder that today in Mexico, even among those of European descent, there is a profound sense of identification with the Mexica as against the Spaniards. Moctezuma himself, who was kidnapped by Cortés and became the victim of a highly pronounced Stockholm syndrome, is barely remembered. The true hero, the Mexican emperor with statues raised to him across the country, is his successor Cuauhtémoc, who fought the invaders to the terrible end. It is not as freedom fighters, however, that the Mexica are most potently commemorated in their native land, but rather as the denizens of a lost and innocent Eden.
A vision which enshrines the conquistadors as syphilitic slave-drivers, practising genocide in the cause of plundering gold, is to be found in the very heart of Mexico City, the great capital raised over the ruins of Tenochtitlán, right on the site of Moctezuma's main palace. Here, in the Palacio Nacional, seat of Spanish viceroys and Mexican presidents, the country's greatest modern artist, Diego Rivera, painted a series of murals illustrating Mexico's history in the 1920s. The blue blood of the Spanish aristocracy might have run through Rivera's veins, but he was also a Marxist with a passionate sympathy for the indigenous peoples displaced by his ancestors. Accordingly, in his murals, he portrayed Tenochtitlán as a workers' paradise where all was dignity, joy and calm.
The beauty of the natural world and the egalitarianism of the social order are represented as having existed in perfect harmony. Rivera shows Moctezuma, who mistook Cortés for Quetzalcoatl, the "feathered serpent" god, not to have been so wrong, after all: the Europeans may not have been gods, but they were certainly snakes in the garden.
This is a perspective that appeals far beyond Mexico. Hugo Chávez is only the most prominent of a generation of South American leaders who have followed in Rivera's footsteps, and found sustenance for their socialist principles in the seedbed of the pre-Columbian past. Evo Morales, the jumper-wearing president of Bolivia, has made much political capital out of being his country's first fully indigenous head of state since the death of the last Inca emperor. "Lula" da Silva, the charismatic president of Brazil, mortified Gordon Brown at a press conference by lecturing him on the sins of "white people with blue eyes" and pointing out, with reference to the global recession, that he had never met an indigenous banker.
So, what Cortés was to the 16th century, according to this demonology, Goldman Sachs is to the present: because, before the coming of the Europeans, so Chávez has declared, the indigenous people of the Americas lived under a model system of society, "in which there was no private property". This hostility towards globalisation is reflected perfectly by Chávez's substitution of the old Columbus Day celebrations with "Indigenous Resistance Day".
Yet there is a problem with any attempt to follow in Rivera's footsteps, and imply that the west alone introduced the evils of imperialism to the New World. Moctezuma may have died as a martyr to Spanish greed, but before Cortés arrived he had enjoyed a strikingly successful career as a theocratic monarch. Not only had he presided over a pronounced fossilisation of the already rigid social structures of his empire, but he also relished what he saw as his right to conquer whomsoever he wished. No socialist, he. In what must rank as one of the most premature rhetorical questions ever uttered, he had exulted that there were no fresh horizons for his people to conquer. "Are we not," he demanded, "the masters of the world?" And unlike the Spaniards, who were torn between revelling in the fruits of their empire and questioning the potential cost of it to their souls, the Aztecs' approach to imperialism had been red-blooded through and through.
In Rivera's mural of Tenochtitlán, the great temples of the city are painted a pure and unblemished white. In truth, there would seldom have been a day when their steps were not caked with human gore. Even to the conquistadors, hardly strangers to slaughter, the Aztecs' relish for sacrificing prisoners appeared shocking and demonic. After their victory they stamped the practice out, enthroning in its place the rituals of the Catholic Church. In the 16th-century monks and friars who laboured to plant a new religion in Mexico, we can see the predecessors of the sati-banning Napier and those today who campaign in the west against female circumcision or the persecution of homosexuals in foreign lands.
Were they wrong? Even the most convinced cultural relativists, if they are honest, will contemplate the Mexica pantheon displayed at the British Museum exhibition with a slight gingerliness: Huitzilopochtli, the guardian divinity of the Mexica, in whose honour the great temple of Tenochtitlán is said to have been consecrated with the blood of 10,000 victims; Xipe Totec, "Our Lord, the Flayed One", whose priests would wear the skins of those offered to their patron and stab their penises with cactus thorns; Tlaloc, god of the rains, the most primordial god of all, and perhaps the most unsettling, whose favour could be won only by the sacrifice of small children who had first been made to cry.
If these gods were still demanding their tithes of blood today, western public opinion would not hesitate to condemn them. But several centuries later, facing our own environmental crises, we are now better placed to appreciate the dread that drove the priests to make their frantic blood offerings. Dread that the world would darken, dread that it would turn to dust. Without sacrifice, so the Mexica believed, the gods would weaken, chaos descend, and the sun itself start to fade. Only chalchiuatl, the "precious water" pumped out by a still-beating heart, could feed it.
The Mexica certainly had good cause to fear how ephemeral might be the works of man. North of their beautiful city, across the lake, there stood another metropolis: Teotihuacán. This, too, had great temples and palaces, and had once boasted a population of 200,000, no less prodigious than that of Tenochtitlán. All, however, had vanished - and so completely that today we do not even know the name of the people who lived there. The Mexica honoured them as "wise men, knowers of occult things, possessors of tradition", and Moctezuma would often make a pilgrimage to Teotihuacán on foot. He could have had no more awesome a warning that the world was mutable and constantly threatened with collapse, than to gaze upon the wreckage of such a wonder. Whatever the proximate causes of the city's fall in the 7th century AD, few archaeologists today doubt the ultimate reason: the exhaustion of the ecosystem on which it had depended. Teotihuacán died because it had lived fatally beyond its means.
So those who imagine that Mexico before the coming of the Europeans was some kind of prelapsarian paradise could not be more wrong. For all that the Mexica did not use the language of environmental science, they knew that the human order was fragile and dependent on the vagaries of the sun. The metaphors of the Mexica's pre-Columbian religion possess a haunting relevance in today's globalised world, with its insatiable appetite for natural resources, its addiction to the apparently all-conquering technology of the west and its climate that gives rise to increasing nervousness. To visit the British Museum's magnificent exhibition, and survey the wondrous yet terrifying fragments of an obliterated civilisation, is to shiver with a sense of unexpected kinship.
What sacrifice - whether sacrifice of blood or not - might we ourselves be obliged to make to the mysterious forces that hold our planet in their grip?
What horrors, should we fail to make one, might end up closing in on us?
Are we in the west, the heirs of Cortés, the Aztecs of our time?
“Another time it will be like this," ran a proverb of the Mexica, "another time things will be the same, some time, some place. What happened a long time ago, and which no longer happens, will be again. And all will be done again as it was in far-off times."
The "Moctezuma: Aztec Ruler" exhibition is at the British Museum, London WC2, until 24 January 2010
Tom Holland's most recent book is "Millennium: the End of the World and the Forging of Christendom" (Abacus, £9.99).