When has any such thing been even heard or seen; in what annals has it ever been read that houses were left vacant, cities deserted, the country neglected, the fields too small for the dead and a fearful and universal solitude over the whole earth? Oh happy people of the future, who have not known these miseries and perchance will class our testimony with the fables.
The invention of agriculture in several independent locations around the world roughly ten millennia ago has been described as the worst mistake in human history.1 Farming and living in permanent settlements allow the production of food surpluses and enable higher female fecundity, both of which support population growth, but there can be no doubt that it hasn’t been good for human health. The switch from hunting and gathering to cultivating crops and raising livestock certainly led to a contraction of dietary diversity and a higher incidence of nutritional deficiencies; it also required humans to spend more time and energy producing the calories they needed. And there was another unintended consequence of the transition to agriculture – pestilence.
Unlike hunter-gatherers, who may achieve a kill in the wild and immediately butcher and eat the flesh, pastoralists get a reliable source of meat and hides. And of course, grazing herds kept on pasture are also very effective at transforming plant material that is inedible to humans into protein-rich meat. Animal husbandry also supplies other valuable resources, known as secondary products, that are unavailable to hunters. These include nutritious milk, wool and muscle power: beasts of burden carry heavy packs and pull ploughs, wagons and chariots. But all this involves a much more intimate relationship with animals; people and animals have often lived together in the same abode for warmth, which provided pathogens with a prime opportunity to evolve to jump the species barrier and infect humans. We were given the common cold from horses; chicken pox and shingles from poultry; influenza from pigs or ducks; smallpox and tuberculosis from cattle; and measles from dogs or cattle.2 Mumps, diphtheria, whooping cough and scarlet fever were also all originally animal diseases that vaulted into human populations.3 Others seem to have originated in vermin attracted to our food stores and homes, such as leprosy, which comes from mice.4fn1
While some human diseases are believed to be ancient, such as malaria – with which, as we have seen, humanity has had a long evolutionary relationship – most diseases broke into the human population after we adopted agriculture and began to live with domesticated animals.
Agriculture enabled humanity to live in sedentary societies with ever-denser concentrations of people. This close packing of potential hosts provides the perfect conditions for a pathogen to spread rapidly as a crowd disease. What’s more, throughout history, towns and cities have often made unsanitary environments, with people living among rotting refuse and sewage, thereby contaminating their own water supply. (Hunter-gatherers and nomadic pastoralists, on the other hand, don’t face such problems: they simply move on.) All of these developments led to a surge of infectious diseases breaking into the human population.
So while agriculture bequeathed us glittering cities, flourishing commerce and other fruits of civilisation such as writing, these extraordinary gifts came at a price. Like an ancient, prehistoric Faustian pact, the cost of farming and civilisation was the emergence of plagues.
While large outbreaks of disease likely ripped periodically through the cities of the earliest civilisations in Mesopotamia, Egypt, Northern India and China, there is no surviving written record of these first epidemics. And as populations increased across Eurasia, creating ever-denser towns and cities, different areas would have developed their own local set of circulating infectious diseases. But it was when trading networks extended and began to connect the major population centres, ports and entrepôts that pathogens were able to spread far and wide, always finding fresh hosts to infect.
Warfare is invariably associated with the spread of disease. Soldiers drafted from disparate provinces and then packed closely together in large numbers in squalid camps created prime conditions for the mixing and propagation of the pathogens they brought with them. When invading far-flung regions, they were exposed to new, local diseases, while transmitting their own to the native civilians; and when returning from foreign locales, they brought back new diseases to their homelands.6
Disease has always exacted a punishing toll upon armies on the march or laying siege, adding to their general exhaustion and malnutrition, but accurate figures only became recorded from the nineteenth century. In the Crimean War of the mid-1850s – to which we’ll return in Chapter 8 – Britain lost ten times more troops to dysentery and typhus than to actual combat with the Russians. By the end of the century, in the Boer War fought against Dutch settlers for control of South Africa, the British Army lost five times more men to microbes than enemy action.7 In fact, the first major conflict in which more combatants were actually killed by each other rather than attendant disease was the Russo-Japanese War of 1904–5 (and was only true for the Japanese). But even in the First World War, when millions of young men were rammed through the meat-grinder of industrialised slaughter on the Western Front, in the eastern theatre both sides still lost more men to disease than to enemy action. It was only by the time of the Second World War, and the arrival of widespread sanitary measures, infection control, vaccinations and antibiotics, that other humans had finally become more of a threat than microorganisms.8
The Four Horsemen of the Apocalypse, believed to be punishments sent by God, are Pestilence, War, Famine and Death. The disruption to society caused by war – young men being torn away from their farms to die in some remote land while an invading army plunders stored grain and livestock – often led to food shortages and famine. Malnourished, weakened people, often driven from their homes, are much more susceptible to disease. Throughout history, therefore, war has not only routinely decimated whole armies but spread pestilence and triggered epidemics across the civilian populations. The Thirty Years War, for example, fought mostly within the Holy Roman Empire in the first half of the seventeenth century, saw total military casualties of just over half a million – up to two-thirds of which were caused by disease.9 But the numbing tragedy of this conflict, and perhaps the greatest medical catastrophe of human history, is that up to 8 million civilians also perished. Here too only a tiny percentage were killed by direct military action; the vast majority succumbed to starvation (12 per cent) or disease (75 per cent) caused by the disruption of the war.10
Yet trade has been as important through history in spreading disease and triggering epidemics as war and the march of armies.11 In the first millennium BC, civilisation in Eurasia passed through a key transition when the numerous, densely populated cities became connected through extensive trade networks.12 This ushered in the age of devastating crowd diseases and raging epidemics.
The Plague of Athens is the first known epidemic in recorded history, and struck the city in 430 BC, at the beginning of the Peloponnesian War with Sparta. It also spread around the eastern Mediterranean, but with less devastating consequences than in the overcrowded city, where it killed between a quarter and a third of the inhabitants.13 The plague was recorded by the Greek historian Thucydides, who caught, but survived, the disease and described symptoms including a raging fever, livid patches on the skin, vomiting, severe diarrhoea and convulsions. Athenian society fell apart, as the populace ‘became indifferent to every rule of religion or law’14 and descended into widespread debauchery and crime, believing they were already living with a death sentence.15
Plagues would become a recurring feature of history.
In its heyday in the second century AD, as the capital sat at the heart of a sprawling empire stretching right around the Mediterranean, Rome was particularly prone to the outbreak of epidemics. While it was exemplary at the time for its use of sanitation and for protecting the public water supply from contamination, it was still an extremely crowded city with a population of around one million – the largest in the world at the time. Its traders moved freely across vast areas, and its armies marched to all corners of the known world, creating a network of super-highways for microbes. And all roads led back to Rome.16 Not only was there the potential for pathogens from far and wide to enter the capital, but the crowded city also provided the perfect conditions for their rapid spread as epidemics.
The so-called Antonine Plague struck the Roman army while battling its age-old rival the Parthians in Mesopotamia at the end of AD 165, and the troops brought it back to Rome the following year.17 It spread rapidly across Eurasia, reaching as far as India and China, with successive waves recurring until the early 190s.18 According to the contemporary physician Galen, the symptoms included a scabby skin rash, fever, bloody stools and vomiting,19 but we don’t know the exact nature of the disease: it could have been smallpox, measles or maybe typhus.20 But we do know it was deadly: the Antonine Plague is believed to have killed between 10 per cent and 30 per cent of the Roman population.21
The Plague of Cyprian, named after the Christian bishop of Carthage who witnessed and described it, struck next. Originating in Ethiopia in 249, the epidemic spread across North Africa, through the entire Roman Empire and into Northern Europe, recurring in waves for the next two decades. Again, the causative agent is unclear, but like the Antonine Plague it may have been smallpox or measles, or perhaps a haemorrhagic virus similar to Ebola.22 The plague claimed two emperors, Hostilian and Claudius II, and about a third of the population of the Roman Empire – possibly as many as 5 million people.23
This epidemic is believed to have been a major contributing factor to the so-called ‘crisis of the third century’, which led to a rapid transformation of the empire between 250 and 275.24 The financial system disintegrated, and political turmoil destabilised the ruling elite. An army weakened by disease was stretched thin along the empire’s lengthy frontiers, unable to repel constant raids and invasions from barbarian tribes or the deep territorial incursions from the rival Sassanian Empire. But perhaps the most significant long-lasting effect of the Plague of Cyprian was the rapid spread of a particular religion.
The mortality and existential crisis caused by the plague made many Romans lose faith in their traditional polytheistic religion, with its pantheon of fractious and devious gods.25 At the time, Christianity was a relatively obscure and somewhat radical cult,26 but what made it stand out now was that it preached community-minded charity and care for the sick as a righteous duty.27 Christian churches throughout the empire responded to the crisis of the plague by encouraging their members to care for those suffering from the disease, even at the risk of catching it themselves. Before the arrival of modern medical practices, nursing – being kept warm and helped to eat and drink – could make a significant difference to an individual’s chances of recovery and survival. As a result, the Christian communities would have enjoyed slightly higher survival rates of the plague; but what’s more, any pagans who benefitted from Christian charity and were nursed back to health would have felt significant gratitude and commitment to the religion that had saved them. And the prospect of a heavenly afterlife, accessible to those who had lived a virtuous and charitable life, as preached by Christians, surely held a particularly strong appeal during the rampant death of a severe epidemic.28 While many other institutions were failing, the Christian Church was bolstered by the unfolding devastation of the plague.
This marked the beginning of the rapid spread of Christianity across the empire, despite the fact that its followers were still persecuted for their beliefs by the Roman authorities. Persecution ended when Emperor Constantine issued the Edict of Milan in 313; and in 380, Theodosius declared Christianity Rome’s singular state religion. As a result, Christianity would be the dominant religion in Europe and the West for the next 1,500 years
By the end of the fifth century, the Western Roman Empire had collapsed under the pressure of invading barbarians, while the eastern half survived as the Byzantine Empire, with its capital at Constantinople. Byzantine culture, scholarship and architecture flourished under the rule of Emperor Justinian I (527–565), and the magnificent Hagia Sophia was constructed. Justinian also rewrote the body of Roman laws, which came to serve as the basis of the Napoleonic Code 1,200 years later, and thereby influenced law-making in much of continental Europe and around the world. But perhaps Justinian’s most ambitious project was his bid to reconquer the lost territories in the west in order to resurrect the glory of the unified Roman Empire.
In this, he was largely successful, at least for a time. Justinian’s armies successfully crushed the Vandal Kingdom to reclaim North Africa; recaptured the southern portion of the Iberian Peninsula to establish the province of Spania; and conquered the Ostrogothic Kingdom to restore the Dalmatian coast, Sicily and Italy, including Rome itself, to the empire. Justinian also launched repeated campaigns against his powerful eastern neighbour, the Sasanian Empire.29
But these successes proved short-lived when biological catastrophe struck. The year 541 saw the arrival of one of the most deadly and feared diseases in human history: the bubonic plague.30 DNA extracted from skeletons dating to the period confirm that the Justinian Plague was caused by Yersinia pestis, the same flea-transmitted bacterium behind the medieval Black Death and mid-nineteenth-century epidemics of plague.31
The first plague epidemic is believed to have originated in the Central Asian highlands near the Tibet-Qinghai Plateau and probably travelled with seaborne trade across the Indian Ocean and up the Red Sea.32 When it reached the Egyptian port of Pelusium it ripped across the busy trade networks around the Mediterranean Sea and throughout the Byzantine Empire, hitting Constantinople in 542.33 Justinian’s enemies weren’t spared: the epidemic spread across the Sasanian Empire in Persia, too.34 The historian Procopius, who witnessed the devastation, wrote, ‘During these times there was a pestilence, by which the whole human race came near to being annihilated … it embraced the whole world, and blighted the lives of all men.’35
Between a quarter and half of the population of Constantinople was wiped out within two years,36 and between 25 million and 50 million people across Europe and around the Mediterranean perished.37 With its devastating death toll, the Plague of Justinian is regarded as the third-worst epidemic in human history, after the Black Death of the 1340s and the influenza pandemic of 1918.38
The initial surge had passed by 550 AD: after raging through the population, it burned out when it could infect no more susceptible individuals. But fresh outbreaks recurred over many years – a common feature of epidemics, whereby the disease is able to sweep back across a region when the acquired resistance in the population is fading or new generations of susceptible individuals have been born. The plague reverberated through history until the mid-eighth century, when the disease finally receded from Europe, the Mediterranean and the Middle East.39
The mass depopulation resulting from the Plague of Justinian caused significant socioeconomic upheaval across the Byzantine Empire.40 Trade around the Mediterranean faltered, leading to a prolonged period of economic instability.41 Fiscal records from the plague years reveal a dramatic decline in tax revenue,42 squeezing imperial expenditure, especially on the army.43 By 588, army pay had been cut by a quarter, and rebellions among soldiers were breaking out along the eastern borders.44 The damage to the empire’s finances and military lasted for generations,45 and before long, the recently reconquered territories in the west – North Africa, most of Italy, Greece and the Balkans – were lost again.46 The decline of the Byzantine Empire following the recurring waves of plague marked the end of the ancient world – the classical age of the great Greek and Roman civilisations – and the beginning of the Middle Ages.47 The centre of European civilisation moved from the Mediterranean rim towards Western and Northern Europe.48
The conflict between the Byzantine and Sasanian Empires continued into the seventh century, further weakening both sides which had been hit equally hard by successive waves of plague. This left the region vulnerable to a newly rising power – the armies of Islam.49
Muhammad was born in Mecca around 570, and by the time of his death aged 62, he had united the tribes of the Arabian Peninsula. The Byzantines first clashed with advancing Islamic armies in the late 620s, when Muhammad was still alive, but neither the Byzantine nor Sasanian Empires were able to mount much resistance.50
Living as nomads in low population densities, the peoples of Arabia had been less severely affected by the recurring outbreaks of plague than those in the dense towns and cities of the Roman and Persian Empires.51 After uniting the tribes under a new religion, Muhammad had died in 632, but his successors conquered huge territorial areas of the Byzantine Empire and caused the complete collapse of the Sasanian Empire in 651. By 750, first under the Rashidun and then the Umayyad dynasties, the caliphate had expanded from the Arabian Peninsula to stretch west across North Africa to the Iberian Peninsula, and east throughout Persia to the Indus River. The Islamic empire rapidly filled the power vacuum left by the decline of the two superpowers in the region, which had been weakened by the waves of plague and war with each other.52
Eight hundred years after the Plague of Justinian, Yersinia pestis returned to western Eurasia with a vengeance – as the Black Death.
This medieval outbreak of the plague may have been triggered by the military campaigns of the Mongols through the Gansu corridor – leading between mountains and desert into the plains of China – possibly as they hunted rodents for meat and fur.53 It seems that from here, plague-carrying fleas travelled with the Mongol army and then with merchants and their wares along the Silk Roads trade network westwards to the Middle East and the Black Sea, where the epidemic entered Europe. An early instance of biological warfare is recorded from the time. Caffa (now Feodosia in Ukraine) on the Crimean Peninsula was one of the main trading ports of the maritime republic of Genoa, permitted by the Mongolian khan to operate within his empire. But relations soured, and the Mongol army of the Golden Horde laid siege to Caffa in 1346. Unable to capture the fortified port, the besiegers catapulted over the stronghold walls the corpses of the men who had died of plague breaking out in their camp. The fortress fell, and the fleeing inhabitants are believed to have spread the plague to Europe.54
Whatever its exact route, the plague reached Europe in the autumn of 1347, with ships from the east docking at the ports of Sicily, their crews already dead or dying of the strange new disease. The sailors were suffering from high fever, vomiting, acute headache and delirium; and their bodies were marked with protruding, dark boils in their necks, armpits and groins,55 which not only were exceedingly sensitive but also made strange gurgling sounds.56 These characteristic boils were due to the plague bacterium infecting the lymph nodes in the body – in fact, the word ‘bubonic’ derives from the Greek boubṓn, meaning ‘groin’.57fn2
From Sicily the plague passed into mainland Italy and then spread quickly along the Mediterranean coast to France and the Iberian Peninsula, while reaching Byzantium by ship. Florence was hit particularly hard, with the pestilence wiping out 60 per cent of the city’s inhabitants. As with other epidemics, the plague was far worse in the cramped, squalid conditions of towns and cities, spread rapidly by rats infested with plague-laden fleas, or perhaps by lice;59 but rural areas were also severely struck. By spring 1348, the whole of Southern Europe was aflame with the Black Death, and the infection was heading north overland.60 It crossed the English Channel later that year to strike London, killing almost half of its 60,000 inhabitants.61 Once infected, victims often died within a matter of days.62 And the plague was an indiscriminate killer, felling old and young, male and female, rich and poor, with equal ferocity. So many people succumbed that the cemeteries overflowed and trenches were dug into which bodies were piled in mass burials.
By 1353, when it began to recede, the Black Death had spread its deathly veil across the whole of Europe, North Africa and the Middle East,63 killing somewhere between one-third and two-thirds of the population. In all, within just a few years, some 50–100 million people had died – it would take over two centuries for populations to recover to their pre-plague levels. The Black Death was the greatest demographic catastrophe ever to strike the human race. The influenza epidemic of 1918 may have killed a greater number of people, but by then the global population had increased hugely. In terms of the sheer mortality rate among those infected – between 50 and 60 per cent – the Black Death was by far the deadliest disease in history.64
The short-term effects of the Black Death were profound. The catastrophic loss of life inflicted unspeakable psychological trauma on survivors who witnessed the demise of a huge proportion of their community, in many cases including much of their own families. Society was paralysed, stunned by the apocalyptic event, and survivors gave themselves over to earthly pleasures, without care for the future. People also suffered from a profound disruption of economic activity.
But in the long term, as Europe recovered from the colossal shock to social and economic structures, there were some beneficial outcomes – a silver lining to the storm cloud of bubonic plague.
Feudalism was the social system in place across Europe in the fourteenth century. Extensive tracts of land were owned by a lord of the manor and passed down the family. Rural peasants were permitted to grow their own crops on parcels of the land in return for labour, and they also had to serve as soldiers when the call to arms came from the king. The mass depopulation caused by the Black Death shook this system to the core.
The deaths of large numbers of the lower classes created an acute shortage of both unskilled labourers on manor lands and skilled artisans and tradesmen in the villages and towns. With labour becoming more valuable, peasants and craftsmen gained bargaining power. Labourers left their manors in search of a better deal. The nobility and governments attempted to control the situation by imposing limits on wages and prohibiting the movement of serfs, but these measures largely failed. Although the restrictions were brought in for the benefit of the feudal lords, it was still in their own best interests to turn a blind eye and accept labourers who were wanting to move – so they were quite happy to poach much-needed workers from their neighbours.65 With people travelling in search of better work, feudal ties to the manor were weakened.
The extraordinary death rate also meant that large areas of land were now unoccupied and without a surviving owner, and these were transferred to those relatives within the gentry who were still alive. As more land was held among fewer landowners, its value dropped. Plots were sold to peasant farmers who had never owned property before.
Overall, any severe mortality crisis can be expected to lower inequality in society: when labour becomes more scarce, real wages rise, reducing the income disparity between the richest and poorest in society. We have solid evidence that this is exactly what happened after the Black Death.66 Such a drop in wealth inequality also led to a reduction in capital income inequality, as a larger section of society now had both the means (from higher wages) and the opportunity (due to more land being available, more cheaply) to acquire property of their own.67 What’s more, increased mobility and wages also created a higher general standard of living.
Feudalism was beginning to break down. The system of payment by labour for access to land started to be replaced by receiving wages and paying rent – a shift from indentured serfdom to monetary transactions. This led to a more market-oriented economy68 and a freer, more mobile society. The Black Death didn’t immediately end the feudal system of lord and serf – in England, it didn’t disappear until the sixteenth century, and it continued even longer on the continent – but the social conditions created in the aftermath of such a mass depopulation certainly accelerated its demise in parts of Western and Northern Europe.69fn3
As well as empowering individual peasants, depopulation transformed European agriculture. At the beginning of the fourteenth century, Europe’s population – although only about one-tenth of what it is today – was pushing right up against the carrying capacity of the cultivable land with medieval crop varieties, tools and farming techniques. Most available land was put to harvesting staple cereal crops, such as wheat, to feed the masses. Market prices for basic foodstuffs were high and the lack of dietary diversity led to malnutrition. Crop rotation systems were often suspended so as to grow much-needed grain even on the fallow fields. This resulted in nutrient-depletion and exhaustion of the soil, and crop yields dropped further. In the years before the arrival of the Black Death, there had been a succession of increasingly severe crop failures – and famines – possibly also linked to a climatic shift to colder, wetter conditions.72 Much of fourteenth-century Europe was therefore locked in a vicious cycle known as the Malthusian Trap73 – the population had grown until it was limited by agricultural production and lived in widespread poverty at subsistence level. Before the Black Death, Europe was a stagnant, overcrowded continent.
The Black Death shattered this deadlock.74 The population collapse meant arable land no longer had to be used to grow just grain to feed everyone, resulting in a diversification of agricultural produce. Food became more plentiful and therefore cheaper for the average peasant and town-dweller, and standards of living rose. Just as significantly, marginal land which had been brought under the plough reverted to woodland or pasture for livestock. Sheep farming is more land-intensive but also more labour-efficient, well-suited to the smaller population – only a handful of shepherds are needed to tend huge flocks of sheep. The growth of the wool industry further invigorated local economies,75 and wool export transformed the English economy in particular in the late-medieval period.
The long-term historical repercussions of the demographic catastrophe of the Black Death – higher wages, lower food costs, higher living standards, greater social mobility – created a more diversified society and economy in Western Europe. The plague devastated fourteenth-century Europe, but the green shoots of recovery grew back stronger.
This second period of plague in Eurasia remained a threat for the next three centuries before finally fading away again in the late seventeenth. Over this time, the disease flared up in irregular outbreaks, and in fluctuating severity, across different regions. Thus the last great plague outbreaks of 1629–1631 and 1656–1657, for example, hit Southern Europe much harder than the north,76 killing up to 4 million people in Italy, 2.2 million in France and 1.25 million in Spain. There were less than half a million English victims in these final outbreaks (although the Great Plague of London in 1665–1666 killed almost a quarter of the city’s population).77
Some historians believe that the Black Death, and subsequent waves of plague, was a contributing factor behind the Western world coming to overtake eastern civilisations such as those of India and, in particular, China from the sixteenth century in terms of economic, technological and industrial development – the so-called ‘great divergence’. The argument is that in western Eurasia, the plague established a persistent pattern of high mortality and high income, which created a favourable environment for a series of socioeconomic and political reforms that invigorated faster development and enabled the West to pull ahead. China was less heavily impacted by the plague between the fourteenth and seventeenth centuries and therefore remained locked in the Malthusian Trap, its population living in a state of subsistence at the limits of the carrying capacity of the land.78
Still, China was also affected by the plague, with an outbreak of the disease in 1633–1644 believed to have contributed to the fall of the Ming dynasty, which had ruled the empire for almost three centuries. Ming China had already been in decline by the early seventeenth century, but the impact of plague knocked out the last teetering supports. Severe epidemics broke out in Beijing and the region north of the Yangtze. Crops were not planted or harvested, food supplies dwindled and grain prices soared as the commercial economy shut down. With no one able to pay taxes, the imperial treasury ran empty. The government wasn’t able to pay the army to quell the peasant revolts breaking out in the provinces or repel the Manchu invaders that attacked the Great Wall. When, in April 1644, a rebel army captured Beijing, the last Ming emperor hanged himself from a tree outside the Forbidden City, and the Manchus then established the Qing dynasty.79
Columbus’s 1492 voyage to the Americas marked the start of centuries of European conquest, colonisation and exploitation of the New World. The exploration of the twin continents by the Spanish and Portuguese also triggered a global redistribution of natural resources, known as the Columbian Exchange. Domesticated plants and animals native to the Americas – such as maize, potato, tomato, chilli, tobacco and the turkey – entered the Eurasian diet, while Old World domesticates like wheat, rice, cattle, pig, sheep, chicken and horse were transported to the Americas. But what’s more, the Columbian Exchange marked the greatest redistribution of microbes in human history.
After Columbus’s first contact, the Spanish continued exploring the islands of the Caribbean and the eastern coastline of the Central and South American mainland, establishing settlements across newly claimed territories. There were rumours of great empires inland – complex civilisations that could supply the gold riches the Spanish yearned for – and privately funded mercenary armies embarked on expeditions into the interior.
Hernán Cortés landed on the Yucatán coast in 1519 and marched on the capital of the Aztec Empire, Tenochtitlan (today’s Mexico City), with just sixteen horsemen and around 600 foot soldiers.80 The Spanish were initially peacefully received, but when they took the Aztec emperor, Moctezuma, hostage they were forced to flee the city, losing many men in the retreat. Hopelessly outnumbered, the Spanish braced themselves for a final, crushing attack – but it never came. Smallpox, brought to the New World by the Europeans, had already begun to rip through the highly susceptible population. The Spaniards returned to Tenochtitlan and laid siege to the city for seventy-five days.81 When they finally entered the Aztec capital, they encountered a ghost town, with the stockades, houses and streets littered with corpses82 – victims of the European-brought pestilence.83
The disease stalked from village to village through the entire Yucatán region, killing so many that there weren’t enough people left alive to farm the fields. Famine followed, and before long, the Aztec civilisation had collapsed. The survivors submitted to Spanish control. By the time the Aztec state had fallen in 1521, smallpox was already spreading into South America along trade routes, soon reaching the Andes and the heart of the Inca Empire.84
A decade later, in 1531, another Spanish company of just 62 horsemen and 106 foot soldiers,85 led by Francisco Pizarro, landed on the coast of Peru to launch an expedition into Incan territory. Smallpox had already wrought its devastation, killing around a third of the population. The emperor too had died, triggering a succession crisis and civil war.86 Pizarro met no significant military resistance to his invasion and captured the new emperor, Atahualpa, whom he held hostage for eight months, demanding a huge ransom of gold for his safe release. After the gold was gathered from across the empire and delivered to the Spanish, Pizarro had him executed anyway.
The European conquerors had a technological superiority over the warriors of the native civilisations of the Americas. Their bronze weapons, bows and arrows and slings were no match for Spaniards’ canons and muskets, cavalry horses and razor-sharp steel swords.87 But the decisive factor in the clash between the Old and New Worlds was not military but epidemiological.88 Cortés did not conquer an empire of an estimated six million Aztecs, nor did Pizarro’s defeat ten million Inca:89 both were destroyed by new diseases.
Smallpox had been present in the Old World causing outbreaks for millennia, perhaps from as early as 3,500 years ago in Egypt, India and China.90 While it utterly decimated the people of the Americas, it still had a deep impact on the history of Europe, despite the population being more resistant. Smallpox struck a young Queen Elizabeth I just four years into her reign, leaving her half-bald and her face pitted with scars, and causing her to rely on wigs and thick cosmetics caked white on her face.91 Seventeenth-century Europe has been called ‘the age of powder and patch’ because of the widespread use of white make-up and small dark beauty spots to hide pockmarks.92fn4
Smallpox also killed a multitude of kings, queens and emperors across Europe (as well as the emperors of Japan and Burma),94 ending dynasties and deflecting the course of succession and disrupting alliances in the French, Spanish, German, Austrian, Russian, Dutch and Swedish royal families.95
In the Americas, measles and influenza showed a greater disparity in their impact on the invading Europeans and the indigenous populations. Europeans still died quite regularly of smallpox,96 but other Old World diseases such as measles and influenza as well as mumps, whooping cough and the common cold were rarely fatal in adults.97 But for the native Americans who had never previously encountered these diseases, and therefore possessed no genetic resistance or acquired immunity, these diseases could each kill around 30 per cent of those they infected. They raged through the susceptible indigenous populations as so-called ‘virgin soil’ epidemics, resulting in near-total population collapse.98 And, as we have seen, when Europeans began transporting African slaves to the Caribbean and Americas, they also introduced the mosquito-borne diseases malaria and yellow fever.99
When European explorers ventured deeper into the American interior, they frequently encountered a post-apocalyptic wasteland, with abandoned villages and deserted, overgrown farmland. So extreme was the Great Dying of indigenous American populations that it even caused a blip in the Earth’s climate. There is a measurable dip in the atmospheric carbon dioxide levels of the sixteenth and early seventeenth centuries, caused by the abandonment of agricultural land and regrowth of forest over extensive regions – perhaps about 56 million hectares – that created a small cooling effect on the global climate.100
The Aztec and Inca Empires were the first to succumb to Eurasian pathogens early in the sixteenth century, when the Portuguese conquest and colonisation of Brazil was also aided by Old World diseases. A hundred years later, they began devastating indigenous tribes further north as well. When the Mayflower arrived at Cape Cod in 1620, savage epidemics of pathogens imported by earlier European explorers had raced ahead of the Pilgrims,101 so they were under the impression that they had set foot on a largely vacant continent, full of fertile but uninhabited land ready for the plough. This would feed into the nineteenth-century concept of the Manifest Destiny – that the westward expansion of the United States was not only justified but inevitable, as settlers populated a largely empty continent that seemed to have been just waiting for them.
By the end of the seventeenth century,102 the full panoply of Eurasian diseases was also endemic in the Americas and constantly swirling around the population, present as the background burden of diseases people are exposed to in their childhood, as they had in the Old World.fn5
It may be impossible to ever determine an exact figure for how many people in the Americas died of epidemics as they were first exposed to Eurasian pathogens. The estimated overall population loss rates are contentious but range from 40 per cent106 to as much as 95 per cent,107 with most recent calculations coming in towards that upper end.108 What seems likely is that the pre-contact population of the Americas in 1492 was around 55–60 million people, which crashed to just over 5 million by 1600.109 Even with the influx of settlers, first from Europe and then from the rest of the world, and the arrival of Africans through the slave trade, it took around three and a half centuries for the population of the Americas to recover from the microbial massacre.110
I have focussed here on the devastating effects of Old World diseases upon the susceptible populations of the Americas, but the contact with European explorers and colonists was just as bad for other previously isolated human populations, such as the Aborigine people of Australia, the Māori peoples of New Zealand, the Khoisan of South Africa and the native inhabitants of Pacific islands such as Fiji.111 Remarking upon the catastrophic decline of indigenous populations after contact, Charles Darwin wrote in his journal in January 1836, ‘Wherever the European has trod, death seems to pursue the aboriginal. We may look to the wide extent of the Americas, Polynesia, the Cape of Good Hope, and Australia, and we find the same result.’112
An important question arises from this. When contact was first established between the Old and New Worlds, why were New World populations devastated by Old World diseases, but not vice versa? It seems that, in this respect, the Columbian Exchange was one-sided.fn6
Humans migrating out of Africa and dispersing around the world reached North America around 15,000 years ago by crossing the Bering land bridge.116 This was a wide corridor of ocean floor, exposed as dry land by the very low sea levels during the last ice age, which linked Siberia and Alaska. From here, they spread south to the Isthmus of Panama and crossed into South America. By around 11,000 years ago, as sea levels rose again with the thawing of the world, the land bridge disappeared beneath the ocean waves and the eastern and western hemispheres of the Earth became biologically isolated from each other.117 The small group of humans that had crossed into Alaska did so before the development of agriculture and the domestication of animals (with the exception of the dog), and therefore before the existence of the many crowd diseases that subsequently emerged in Eurasia. (Other, more ancient diseases such as malaria were not able to cross the freezing Bering land bridge with these first migrants.) So when Eurasia and the Americas became separated again, the human world in the Americas was essentially free of infectious diseases. And significantly, the American populations didn’t go on to develop crowd diseases of their own. They too domesticated wild plant species as crops and developed agriculture and civilisation, but there were very few large animals they could domesticate.
The Aztecs and Incas created sophisticated civilisations that spread across extensive areas, with well-developed transport networks, administration systems and dense urban centres. Indeed, in the early sixteenth century, the Aztec capital Tenochtitlan was among the most populous cities in the world – five times larger than London and on a par with Paris, Venice and Constantinople.118 These New World civilisations would have been as conducive to raging epidemics as the Roman Empire or medieval Europe. There just weren’t any crowd diseases in the pre-Columbian Americas.
This is not to say that before the arrival of the Europeans indigenous Americans lived in some kind of pathogenic Garden of Eden – they still suffered dysentery, intestinal parasites, insect-borne afflictions including Lyme disease119 and tuberculosis.120 But they were spared the scourge of widespread plagues as they’d never lived in close association with large numbers of domesticated animals.121
The Americas, with large populations and no natural immunity to Old World diseases, were like a wide expanse of dry woodland when just a few sparks of disease brought on European ships ignited blazing forest fires that raged across the land.
While the introduction of Old World diseases had catastrophic consequences for indigenous Americans, the response of the European colonists to this great depopulation claimed more victims. The same epidemics that had made the Americas so unable to repel European conquest had also left the colonists bereft of a local population that could be forced into labour on their plantations and mines; so they turned to Africa.
The first slaves transported to American colonies were taken by the Spanish to Hispaniola in 1502 to work the newly established tobacco and sugar plantations and dig mine shafts to find hoped-for gold seams. They arrived from Spain where they had previously been working and had converted to Christianity. When it became apparent that more labour was needed for the economic exploitation of the colonies, the Spanish king, Charles V, ordered in 1518 the direct transport of slaves captured from the West African coastline, marking the beginning of the transatlantic trade route.122 Before long, the concept of race was invented and then reinforced as a colonial construct to dehumanise black Africans and justify seizing ‘others’ as chattel and enslaving them into forced labour.
Demand for African slaves increased with the expansion of the colonies and plantations, and especially after insect-borne diseases such as malaria and yellow fever had become established in the Caribbean islands and tropical regions of North and South America around the mid-1600s.123 European colonists, as well as indentured labourers from their own homelands, were as susceptible to these tropical diseases as indigenous Americans. As we saw in the last chapter, African adults were seasoned against yellow fever and malarial infections and had evolved genetic adaptations to malaria in particular, such as sickle cell and Duffy negativity, that provided resistance. Without understanding the intricacies of the immune system or these red blood cell mutations, Europeans were nonetheless well aware of how Africans appeared hardened against the tropical diseases to which they themselves so helplessly succumbed.124 So unlike in the temperate latitudes of North America (and later Oceania), where migrants from Europe could be attracted to settle and farm, the colonies in the tropical Americas became dependent on imported African labour for their plantation economies. The market price for different labourers reflected their resistance against tropical diseases. Slaves imported directly from Africa were worth three times more than an indentured European labourer and double an indigenous slave; and African slaves who had already been proven to be resistant to the local diseases were worth twice as much as a fresh import.125
The produce cultivated on these plantations was primarily cash crops that could be traded within or between colonies or fetch high prices back in Europe – sugar, tobacco, tea, coffee and, later, cotton.fn7 Unlike staple crops such as wheat, rice or potatoes, these plants were valued not for their ability to feed populations but for other effects on our bodies and brains. We will return to our biological cravings for these often addictive substances in Chapter 6.
In terms of the total number of people killed by a single epidemic, the global influenza pandemic that emerged in 1918 was the greatest killer since the Black Death, and possibly in the whole of human history.126 But it is often discussed only briefly in history books as an endnote to the First World War. With the world already numbed by the horrors of the Great War at the time, the flu pandemic has been described as ‘a global calamity the world forgot’.127
It’s not known where the outbreak originated, but the first documented cases of an unusual respiratory fever were in an army camp in Kansas in March 1918.128 It was being reported in France by April, possibly spread there by soldiers of the American Expeditionary Forces arriving in Brest, the main port receiving troops from across the Atlantic.129 Within a month, grippe had broken out in the French lines, as well as among British soldiers at the camp in Étaples. The symptoms of this new respiratory illness included a high fever, racing pulse and the coughing up of blood. This developed into breathlessness and a distinctive dusky-blue discolouration of the face as the body was starved of oxygen. Autopsies revealed swollen lungs full of thick yellowish pus and haemorrhaged blood – the victims had drowned in their own internal fluids.130 Because of wartime secrecy, the world first heard about the new disease when it spread through neutral Spain in May 1918, where it triggered public alarm and made headline news. The pandemic therefore came to be known, rather unfairly, as ‘Spanish flu’.
The influenza pandemic started off relatively mild, but successive waves became progressively more serious and spread further, with the virus evolving to be more virulent in its human hosts. During the months immediately before and after the end of the war, this influenza strain was killing ten times more infected people than normal flus.131 But the 1918 influenza pandemic was exceptional for another reason. Most flus tend to kill the very young and the old – those with weak immune systems – and so they present a U-shaped death curve. What was odd about the 1918 influenza was that the disease had a pronounced W-shaped death curve: it also killed huge numbers of people aged between 20 and 40 – young adults in their prime.132 Why this might have been is something of a mystery. One possibility is that in the healthiest individuals, the body’s immune system grossly overreacts to the infection in an intense autoimmune response – known as a cytokine storm – that causes extensive lung damage leading to death. Another hypothesis, nicknamed the ‘original antigenic sin’, relates to the way the immune system remembers a pathogen it has previously been exposed to, which then limits how effectively it responds to infections of slightly different variants of the virus later in life.133 The war-time conditions possibly also contributed to the abnormally high mortality of middle-aged people, including crowding in army camps and factories.134 Overall, around half of the victims of the influenza were young adults aged between 20 and 40.135
The war didn’t cause the 1918 influenza – the spillover of the virus from birds into the human population would have happened anyway – but the troop movements and disruption of the war certainly contributed to its rapid spread around the globe. And it’s possible that the trench environment enhanced the extraordinary virulence of this strain. Normally, a pathogen adapts over time to moderate its virulence and keep its host alive longer, so as to be transmitted to more people. But in the conditions of the trenches, where soldiers were hunkered down for weeks at a time in unnatural proximity to one another, with their death rate from other causes already very high, there would have been less selective pressure on the virus to reduce its virulence; and it thus achieved much higher death rates among those infected. Soldiers immobilised by the disease continued to transmit it to those around them, and when those afflicted by the worst variants were brought out of the trenches to a crowded field hospital, it spread among the other wounded and medical staff. Fresh soldiers entering the trenches all the time ensured that the virus always had access to new susceptible hosts.136
The end of the war and demobilisation of troops occurred in the middle of the second wave of the pandemic, in November 1918. Soldiers returning to their families around the world were greeted by packed homecoming parties in the streets, which enabled the virus to spread even more widely.137 A third and less lethal wave rippled around the world in early 1919, before the pandemic finally receded.
All in all, the 1918 influenza pandemic is thought to have infected around 500 million people – one-third of the entire global population138 – killing at least 50 million139 and perhaps as many as 100 million140 of them.141 Most of the deaths occurred in just the few weeks between mid-September and mid-December 1918. In terms of mortality, this influenza pandemic possibly surpasses the First and Second World Wars combined.142
The 1918 influenza caused a huge loss of life, but, like the other epidemics we’ve looked at in this chapter, could this fast-spreading, virulent disease have affected historical events?
When Russia withdrew from the war a year after the Bolshevik Revolution, Germany was able to move many of its forces away from the east. Fifty divisions of experienced troops and 3,000 guns were redeployed to the Western Front,143 so, by April 1918, the Germans had a vast advantage of 324,000 riflemen.144 In several sectors along the Western Front, German forces outnumbered the British and French four to one.145 In March, the German Supreme Army Command launched a new offensive, known as Kaiserschlacht or ‘Kaiser’s Battle’, in an attempt to secure a decisive victory against the Allies before fresh American troops could be fully deployed and turn the tide. The plan was to break through the lines with fast-moving and specially trained stormtroopers to outflank and defeat the British Army, and so force the French to sue for peace.
At first, the spring offensive seemed to succeed. They were able to advance more than 60 kilometres into northern France. When their artillery, now in striking distance of the French capital, began shelling Paris, more than a million Parisians fled.146 But by June, the phases of this spring offensive were faltering.
Logistical problems played a role, but it seems likely that the arrival of the influenza pandemic hit the exhausted German troops harder than their Allied counterparts. German soldiers were malnourished as a result of the Royal Navy’s successful blockading of food imports, and so their resistance to the disease may have been lower than the comparatively well-fed Allied soldiers.147 The flu had also struck the German army three weeks earlier than the Allies, appearing in March and peaking in early July. Although this first wave of the pandemic was much less lethal than the second wave that came in the autumn, every soldier who succumbed was still laid up for several days, and many were left debilitated afterwards.148
Although writing after the war, and largely attempting to exonerate his own failings, the architect of the spring offensive, General Erich Ludendorff, blamed the flu for sickening his men and lowering their morale during the critical period of the Kaiserschlacht: ‘It was a grievous business having to listen every morning to the Chiefs of Staff’s recital of the number of influenza cases, and their complaints about the weakness of their troops.’149 Divisions of 10,000 soldiers were reporting up to 2,000 cases of influenza, and German commanders would only know their unit strength on the day of an attack.150 Over the summer, between 139,000 and half a million German troops were temporarily incapacitated with the sickness.151
Conditions on the home front in Germany were also dire. Severe food shortages due to the British blockade caused an estimated 424,000 excess civilian deaths during the war, compounded by scarcities of coal and warm clothing. A further 209,000 deaths were caused by the flu pandemic – the victims no doubt already weakened by hunger.152 Morale was collapsing within both the military and the civilian populations, and more and more Germans began demanding an end to the war. Many soldiers, utterly demoralised from fighting on the front line, used the flu as a pretext to go AWOL.153
As the strength drained from the German spring offensive, the Allies were only gaining in number as fresh American troops flooded across the Atlantic and onto the Western Front. By July, the numerical advantage had swung back in the favour of the Allies. The following month, their counteroffensives pushed the Central Powers back, undoing the gains made during the spring offensive, before breaking through the German lines in October. By the time the deadlier second wave of the pandemic hit in the autumn, the German army was already beaten. With crushing defeats on the battlefield, and revolution at home, the kaiser was forced to abdicate, and the new Weimar Republic called for an armistice on 11 November.
While influenza further demoralised and weakened German forces, contributing to the capitulation of the German Empire, the horrors of the pandemic brought about unity in another great country, with India able to demonstrate its strength in self-rule.
India was hit particularly hard by the 1918 influenza pandemic, with between 12 million154 and 18 million155 people estimated to have been killed – more than the total number of combatants killed during the war.
The pandemic arrived in India in late May 1918, rippling out of the western port city of Mumbai. As with the pattern found in the rest of the world, this first wave was not particularly worrisome, but when the second, far more virulent variant broke out in September, the results were utterly devastating.156 Death swept through cities and rural villages alike – burial grounds and burning ghats were overwhelmed with bodies. The north and west of India were hit earliest and hardest, with death rates of between 4.5 and 6 per cent. India’s colonial masters, however, were largely insulated from the worst of the devastation. The British were able to take refuge in their large houses, with staff to tend to them if they fell sick, or retreat to their hill stations in the cooler highlands.157 As a result, they experienced a death rate eight times lower than that of Indians living huddled together in unsanitary conditions. The viral pandemic respected privilege.
The inability, or perhaps even negligence, of the British colonial rulers to mitigate the colossal death toll was perceived as one more injustice by those advocating independence. The effects of the second influenza wave in India had been exacerbated by drought and food shortages, but despite an unfolding famine, food grown in India was still being shipped to support the British war effort in Europe. It was clear that the British rulers were prioritising their own interests above the needs of the Indian people.158
Activists of the Indian independence movement – already working in local communities across the caste divides – organised relief centres, distributed herbal medicines and other supplies, and arranged the removal of the dead. Such grassroots efforts and organisation had existed for a while, but the influenza pandemic united them across the country for a single cause. Local leaders were doing their best to address the health crisis that the Raj government seemed to be largely ignoring.159
When the war in Europe ended in November 1918, nationalists hoped for concessions towards much greater Indian autonomy, especially after the huge sacrifices that one million Indian soldiers had made for the British Empire. The Secretary of State for India, Edwin Montagu, had implied in 1917 that India could soon progress to self-government like Canada and Australia, but the actual reforms offered in 1919 shattered this expectation.160 Furthermore, the Rowlatt Act of March 1919 extended the emergency powers granted during the First World War to indefinite imprisonment without trial for sedition,161 effectively continuing martial law in peacetime India. Indians had been expecting more freedom; instead, they were slapped with further repression.
As tensions rippled across the country, one figure rose to prominence in directing the mounting anti-colonial sentiment into effective civil disobedience. Mohandas Gandhi had returned to his homeland in 1915 from South Africa, where he had been working as a civil rights activist, on the urging of a leading politician of the nationalist party, the Indian National Congress. After recovering from a prolonged illness – which may have been influenza during the peak of the second wave – Gandhi called for non-violent resistance against British repression.162 The bubbling discontent and social agitation erupted in spring 1919 with a series of strikes and protests. In the city of Amritsar in the Punjab on 13 April 1919, British soldiers opened fire on a crowd of peaceful protestors, killing hundreds.163
The neglectful mismanagement of the pandemic response, the Rowlatt Act, the Amritsar massacre – all these outrages played into the anti-colonial rhetoric and helped to unite India behind the demand for independence. By 1920, Gandhi had started the non-cooperation movement, urging all Indians to boycott British courts and educational institutions, resign from government positions and refuse to pay taxes. The independence movement had been going for years, but activists like Gandhi could now rely on widespread grassroots support. The virus, and the Raj’s failings in dealing with it, had mobilised communities across India to help the sick; they were now organised to fight for independence. Even so, it took almost three more decades and another world war for India finally to be free of colonial rule.164