CHAPTER 27 
We became orphans, oh my sons!
When humans first walked into the Americas over the Bering Land Bridge fifteen to twenty thousand years ago,* our species existed everywhere as small, wandering bands of hunter-gatherers. There were no cities, no towns, no farming or animal husbandry. We were spread out and moving all the time, only rarely encountering other groups. The low population densities prevented most potential diseases from gaining a foothold. People suffered from parasites and infections, but they did not get most of the diseases so familiar in recent human history—measles, chicken pox, colds, the flu, smallpox, tuberculosis, yellow fever, and bubonic plague, to name only a few.
In the last ten thousand years, as human population densities increased, disease moved into center stage of human affairs. Pandemics changed the very arc of human history. Despite our dazzling technology, we are still very much at the mercy of pathogens, old and new.
In his groundbreaking book Guns, Germs, and Steel, biologist Jared Diamond poses the question: Why did Old World diseases devastate the New World and not the other way around? Why did disease move in only one direction?* The answer lies in how the lives of Old World and New World people diverged after that cross-continental migration more than fifteen thousand years ago.
Farming, which allowed people to settle into towns and villages, was independently invented in both the Old World and the New. The key difference was in animal husbandry. In the Old World, a great variety of animals were domesticated, starting with cattle about eight to ten thousand years ago and quickly moving on to pigs, chickens, ducks, goats, and sheep. New World farmers domesticated animals as well, notably llamas, guinea pigs, dogs, and turkeys. But in Europe (and Asia and Africa), the raising and breeding of livestock became a central aspect of life, an essential activity in almost every household. For thousands of years, Europeans lived in close quarters with their livestock and were continuously exposed to their microbes and diseases. In the New World, perhaps because they had more space and fewer domesticated animals, people did not live cheek by fowl with their animals.
Humans do not usually catch infectious diseases from animals; pathogens tend to confine their nasty work to a single species or genus. (Leishmaniasis is a striking exception.) But microbes mutate all the time. Once in a while, an animal pathogen will change in such a way that it suddenly infects a person. When people in the Near East first domesticated cattle from a type of wild ox called an aurochs, a mutation in the cowpox virus allowed it to jump into humans—and smallpox was born. Rinderpest in cattle migrated to people and became measles. Tuberculosis probably originated in cattle, influenza in birds and pigs, whooping cough in pigs or dogs, and malaria in chickens and ducks. The same process goes on today: Ebola probably jumped to humans from bats, while HIV crashed into our species from monkeys and chimpanzees.
Alongside the domestication of animals, humans in the Old World began settling down in villages, towns, and cities. People lived together in much denser numbers than before. Cities, with their bustle, trade, filth, and close quarters, created a marvelous home for pathogens and an ideal staging ground for epidemics. So when diseases migrated from livestock to people, epidemics broke out. Those diseases found plenty of human fuel, racing from town to town and country to country and even crossing the oceans on board ships. Biologists call these “crowd diseases” because that’s exactly what they need to propagate and evolve.
Epidemics periodically swept through European settlements, killing the susceptible and sparing the robust, culling the gene pool. As always, children were the majority of the victims. Almost no disease is 100 percent fatal: Some victims always survive. The survivors tended to have genes that helped them resist the disease a little better, and they passed that resistance on to their children. Over thousands of years and countless deaths, people in the Old World gradually built up a genetic resistance to many brutal epidemic diseases.
In the New World, on the other hand, no big-time diseases seem to have leapt from animals into the human population. While the Americas had cities as large as those in Europe, those cities were much newer at the time the Spanish arrived. People in the New World hadn’t been living in close quarters long enough for crowd diseases to spring up and propagate. Native Americans never had the opportunity to develop resistance to the myriad diseases that plagued Europeans.
This genetic resistance, by the way, should not be confused with acquired immunity. Acquired immunity is when a body gets rid of a pathogen and afterward maintains a state of high alert for that same microbe. It’s why people don’t normally get the same illness twice. Genetic resistance is something deeper and more mysterious. It is not acquired through exposure—you are born with it. Some people are born with greater resistance to certain diseases than others. The experience of our team in the valley of T1 is a textbook illustration. The doctors believe everyone on the expedition was bitten and exposed. Only half, however, came down with the disease. A few, like Juan Carlos, were able to fight it off without drugs. Others became seriously ill and some, even as I write this, are still struggling with the disease.
The genes that resist disease can only spread in a population through the pitiless lottery of natural selection. People with weaker immune systems (children especially) must die, while the stronger live, in order for a population to gain widespread resistance. A staggering amount of suffering and death over thousands of years went into building European (and African and Asian) resistance to crowd diseases. One biologist told me that what probably saved many indigenous Indian cultures from complete extinction were the mass rapes of native women by European men; many of the babies from those rapes inherited European genetic resistance to disease. (The scientist, after telling me this horrifying theory, said, “For God’s sake don’t attach my name to that idea.”)
In the New World, these many thousands of years of anguish and death were compressed into a window from 1494 to around 1650. The mass murder by pathogen happened in that one cruel century and a half, and it struck at precisely the worst moment, when the population of the New World had recently coalesced into big cities and reached the levels of density necessary for those epidemics to spread furiously. It was a perfect storm of infection.
We do not hear many of the voices of these victims. Only a handful of Native American eyewitness accounts of the cataclysm survive. One in particular stands out, a remarkable text called the Annals of the Cakchiquels, which describes an epidemic, probably smallpox or flu, that swept an area in Guatemala northwest of Mosquitia. This extraordinary manuscript, discovered in a remote convent in 1844, was written in a Mayan language called Cakchiquel by an Indian named Francisco Hernández Arana Xajilá. As a teenager, Arana Xajilá lived through the epidemic that destroyed his people.
It happened that during the twenty-fifth year [1520] the plague began, oh my sons! First they became ill of a cough, they suffered from nosebleeds and illness of the bladder. It was truly terrible, the number of dead there were in that period. The prince Vakaki Ahmak died then. Little by little heavy shadows and black night enveloped our fathers and grandfathers and us also, oh my sons!… Great was the stench of the dead. After our fathers and grandfathers succumbed, half of the people fled to the fields. The dogs and the vultures devoured the bodies. The mortality was terrible… So it was that we became orphans, oh my sons! So we became when we were young. All of us were thus. We were born to die!
I would ask the reader to pause for a moment and ponder the statistics. Statistics are mere numbers; they need to be translated into human experience. What would a 90 percent mortality rate mean to the survivors and their society? The Black Death in Europe at its worst carried off 30 to 60 percent of the population. That was devastating enough. But the mortality rate wasn’t high enough to destroy European civilization. A 90 percent mortality rate is high enough: It does not just kill people; it annihilates societies; it destroys languages, religions, histories, and cultures. It chokes off the transmission of knowledge from one generation to the next. The survivors are deprived of that vital human connection to their past; they are robbed of their stories, their music and dance, their spiritual practices and beliefs—they are stripped of their very identity.
The overall mortality rate in this wave of epidemics was indeed about 90 percent. To put that statistic into personal terms, make a list of the nineteen people closest to you: All but one will die. (This of course counts you also as a survivor.) Think what it would be like for you, as it was for the author of the Cakchiquel manuscript, to watch all these people die—your children, parents, grandparents, brothers and sisters, your friends, your community leaders and spiritual authorities. What would it do to you to see them perish in the most agonizing, humiliating, and terrifying ways possible? Imagine the breakdown of every pillar of your society; imagine the wasteland left behind, the towns and cities abandoned, the fields overgrown, the houses and streets strewn with the unburied dead; imagine the wealth rendered worthless, the stench, the flies, the scavenging animals, the loneliness and silence. Enlarge this scenario beyond towns and cities; enlarge it beyond kingdoms and civilizations; enlarge it beyond even continents—until it embraces half the planet. This inferno of contagion destroyed thousands of societies and millions of people, from Alaska to Tierra del Fuego, from California to New England, from the Amazon rainforest to the tundra of Hudson Bay. It is what destroyed T1, the City of the Jaguar, and the ancient people of Mosquitia.
This is the sort of thing that writers of postapocalyptic fiction put themselves to imagining, the stuff of our greatest news-cycle nightmares—but this very real Armageddon lies beyond reach of the darkest Hollywood movie fantasies. It was the greatest catastrophe ever to befall the human species.
Should sixteenth- and seventeenth-century Europeans be blamed? If one can blame the dead at all, they are answerable. The Spanish, English, and others contributed mightily to the death toll through cruelty, slavery, rape, abuse, starvation, war, and genocide. Europeans killed many native people directly without the assistance of disease. In some instances, they intentionally used disease as a biological weapon by, for example, giving Indians smallpox-infected blankets. And millions more Indians died of disease who might have survived, had European brutality not left them weakened and susceptible.
It is tempting to argue that if Europeans hadn’t arrived in the New World, these deadly pandemics would not have happened. But the meeting of the Old World and the New was inevitable. If Europeans hadn’t carried disease to the New World, Asians or Africans would have; or New World mariners would have eventually reached the Old. No matter what, disaster would have ensued. This was a monstrous geographic accident waiting to happen. This was a time bomb that had been ticking for fifteen thousand years—counting down to that fateful moment when a ship with sick passengers finally set sail across the wide ocean.
This is in no way an apologia for genocide. Still, the catastrophe was largely a natural event, a mindless biological imperative, a vast migration of dumb pathogens from one side of the planet to the other.
There is much irony in the story of our own disease. The strain of leishmaniasis that befell us is a rare example of a New World disease attacking (mostly) Old World people. While I obviously don’t believe in curses, there is an inescapable sense of commination in the fact that a New World city destroyed by Old World disease wreaked havoc on its Old World rediscoverers with a New World disease. But this irony misses the modern lesson: This was a Third World disease attacking First World people. The world is now divided into Third and First, not Old and New. Pathogens once confined to the Third World are now making deadly inroads into the First. This is the future trajectory of disease on planet Earth. Pathogens have no boundaries; they are the ultimate travelers; they go wherever there’s human fuel. We First Worlders have become far too complacent in the idea that disease, especially NTDs, can be quarantined to the Third World, and that we can live safely in our communities supposedly gated against pathogens, ignoring the suffering of the poor and sick in faraway lands.
The HIV medical crisis has already pushed leishmaniasis into new areas of the globe, especially southern Europe. HIV vastly increases the destructive power of leish and vice versa. A leishmania/HIV coinfection is a terrible combination, considered to be a “new” disease all of its own, almost impossible to treat and usually fatal. HIV and leishmania become locked in a vicious cycle of mutual reinforcement. If a person with leishmaniasis gets HIV, the leish accelerates the onset of full-blown AIDS while blocking the effectiveness of anti-HIV drugs. The reverse is also true: A person with HIV who lives where there’s leishmaniasis is a hundred to a thousand times more likely than a healthy person to get the disease, due to a weakened immune system. People suffering from a leish/HIV coinfection are so teeming with the parasite that they become super-hosts, potent reservoirs accelerating its spread. And visceral leish, like HIV, has been shown to be transmitted by dirty needles among IV drug users; two studies in the late nineties found leish parasites on some 50 percent of dirty needles discarded by drug users in Madrid at two different locations several years apart. Sixty-eight percent of all visceral leishmaniasis cases in Spain were among IV drug users.
Leishmaniasis is a disease that thrives among the detritus of human misery and neglect: ramshackle housing, rats, overcrowded slums, garbage dumps, open sewers, feral dogs, malnutrition, addiction, lack of health care, poverty, war, and terrorism. Cutaneous leish is now running rampant in the areas of Iraq and Syria controlled by ISIS—so much so that families there are choosing to intentionally inoculate their young girls with leishmaniasis on a covered part of their body so that they will not get it on their faces, where it will leave a scar. (This type of leish is a mild variety that usually goes away on its own, leaving the person immune.)
Since 1993, the leishmania parasite has been spreading, not just because of HIV coinfection but also as people move from rural areas into cities. It is attacking people who venture into the rainforest for projects such as dam and road building, logging, and drug smuggling, as well as adventure tourism, photography, journalism, and archaeology. Strange tales abound. Almost everyone on a Costa Rican jungle yoga adventure was struck down by leish. A survival show contestant lost part of his ear to leish. A team of filmmakers shooting an adventure tourist video were stricken with leish.
Leish is now spreading in the United States. Over the course of the entire twentieth century, only twenty-nine cases of leish were reported in the United States, all of which occurred in Texas close to the Mexican border. But in 2004, a young man from a small town in southeastern Oklahoma, ten miles from the Arkansas border, visited his doctor complaining of a sore on his face that wouldn’t heal. The doctor cut it off and sent it to a pathologist in Oklahoma City, who was stymied by what it might be and stored the frozen tissue. A year later, this same pathologist, by sheer chance, got another tissue sample from another patient living in the same small town. The pathologist immediately called the Oklahoma State Department of Health and reached Dr. Kristy Bradley, the state epidemiologist. She and her staff ordered the two tissue samples sent to the Centers for Disease Control in Atlanta. The diagnosis came back: cutaneous leishmaniasis, of a mild type that can usually be cured by surgically removing the ulcer. (Both patients were, in fact, cured this way.)
At the time that Dr. Bradley was investigating the disease in Oklahoma, an outbreak of cutaneous leishmaniasis occurred in northeastern Texas and in a string of suburbs in the Dallas–Fort Worth metro area; the dozen or so victims included a little girl who had lesions on her face, and in one case a cat and a human in the same household got the disease. Doctors in the health departments of Texas and Oklahoma joined forces to track the source. They were especially worried because none of the victims had traveled: They had gotten the disease in their own backyards.
Dr. Bradley led the investigation of the two cases in Oklahoma. She assembled a team that included an entomologist and a biologist. When the team visited the patients and surveyed their properties, they noted burrows of wood rats and populations of sand flies, which they concluded must have been the host and vector. The investigators trapped a number of rats and sand flies and tested them for leish. None had the disease, but by this time the mini-outbreak had died down.
I called Bradley and asked if the leish had really died out or if it was still around. “I’m sure it hasn’t gone away,” she said. “It’s smoldering somewhere out there, quietly cycling in nature,” waiting for the right combination of circumstances to break out again. When she and her team mapped leish cases in the United States over time, they revealed an inexorable spread northeastward across Texas and Oklahoma, aiming for other states in a northeasterly direction.
Why?
Her answer was immediate: “Climate change.” As the United States becomes warmer, she said, the ranges of the sand fly and the wood rat are both creeping northward, the leish parasite tagging along. The sand fly genus known to spread this kind of leish has now been found in the United States five hundred miles northwest and two hundred miles northeast of its previously established range.
A recent study modeled the possible expansion of leishmaniasis across the United States over the next sixty-five years. Since it takes both vector and host to spread the disease, the scientists wanted to know where the sand fly/wood rat combination would migrate together. They looked at two future climate scenarios, best case and worst case. For each case, they extrapolated out to the years 2020, 2050, and 2080. Even under the best-case climate assumptions, they discovered that global warming would push leishmaniasis across the entire United States into southeastern Canada by 2080. Hundreds of millions of Americans could be exposed—and this is just by wood rats. Since many other species of mammals can host the leish parasite—including cats and dogs—we know the potential problem is far greater than what was described by this study.* A similar spread of the disease is expected in Europe and Asia.
It seems that leishmaniasis, a disease that has troubled the human race since time immemorial, has in the twenty-first century come into its own. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the NIH, told our team bluntly that, by going into the jungle and getting leishmaniasis, “You got a really cold jolt of what it’s like for the bottom billion people on earth.” We were, he said, confronted in a very dramatic way with what many people have to live with their entire lives. If there’s a silver lining to our ordeal, he told us, “it’s that you’ll now be telling your story, calling attention to what is a very prevalent, very serious disease.”
If leish continues to spread as predicted in the United States, by the end of the century it may no longer be confined to the “bottom billion” in faraway lands. It will be in our own backyards.
Global warming has opened the southern door of the United States not just to leish but to many other diseases. The big ones now entering our country include Zika, West Nile virus, chikungunya, and dengue fever. Even diseases like cholera, Ebola, Lyme, babesiosis, and bubonic plague will potentially infect more people as global warming accelerates.
Modern travel has given infectious disease new ways to spread. Bubonic plague in the fourteenth century traveled from Central Asia to the Levant and Europe by horse, camel, and boat; the Zika virus in the twenty-first century jumped from Yap Island in Micronesia to French Polynesia, Brazil, the Caribbean, and Central America by 2015, all by plane. In the summer of 2016, Zika arrived in Miami, again on an airplane. The 2009 outbreak of deadly H1N1 swine flu in Mexico hitched rides on planes to strike as far away as Japan, New Zealand, Egypt, Canada, and Iceland. As Richard Preston noted in his terrifying book The Hot Zone, “A hot virus from the rain forest lives within a twenty-four-hour plane flight from every city on earth.”
The world’s last great pandemic was the Spanish flu outbreak in 1918 that killed a hundred million people—about 5 percent of the world’s population. If a pandemic like that were to happen again, it would spread faster and might be impossible to contain. According to the Bill & Melinda Gates Foundation, in such a pandemic “the death toll could reach 360 million”—even with the full deployment of vaccines and powerful modern drugs. The Gates Foundation estimated that the pandemic would also devastate the world financially, precipitating a three-trillion-dollar economic collapse. This is not scaremongering: Most epidemiologists believe such a pandemic will eventually happen.
Archaeology contains many cautionary tales for us to ponder in the twenty-first century, not just about disease but also about human success and failure. It teaches us lessons in environmental degradation, income inequality, war, violence, class division, exploitation, social upheaval, and religious fanaticism. But archaeology also teaches us how cultures have thrived and endured, overcoming the challenges of the environment and the darker side of human nature. It shows us how people adapted, lived their lives, and found fulfillment and meaning under fantastically diverse conditions. It tracks both the failures and the successes. It tells us how cultures faced difficulty and challenge, sometimes in successful ways and sometimes in ways that, while successful at first, sowed the seeds of eventual collapse. The Maya created a vibrant and brilliant society that, in the end, failed to adjust to a changing environment and the needs of its people; so did the Roman Empire and the ancient Khmer, to pluck civilizations randomly out of the hat. But the people of the City of the Jaguar did adapt to the challenges of the rainforest, and they continued to thrive in one of the harshest environments on the planet, transforming it into a beautiful garden—until their abrupt demise.
I can recall the very moment when we stumbled over the cache and I first saw that jaguar head coming out of the ground. Gleaming with rain, it rose up snarling, as if struggling to escape the earth. It was an image that spoke directly to me across the centuries—forging an immediate, emotive connection to these vanished people. What had been theoretical for me became real: This spirited image had been created by people who were confident, accomplished, and formidable. Standing in the gloom among the ancient mounds, I could almost feel the presence of the invisible dead. At its zenith, the people of the city of T1, the City of the Jaguar, must have felt nearly invulnerable in their valley redoubt ringed by mountains. What power could overthrow their mighty gods and potent rituals? But the unseen invader ghosted in and visited upon them a destruction that was as impossible to resist as it was to predict. Sometimes, a society can see its end approaching from afar and still not be able to adapt, like the Maya; at other times, the curtain drops without warning and the show is over.
No civilization has survived forever. All move toward dissolution, one after the other, like waves of the sea falling upon the shore. None, including ours, is exempt from the universal fate.