The Next Great Migration

The Next Great Migration Plot Summary

Introduction

Throughout history, humans have been on the move. We've crossed oceans, traversed mountains, and ventured into unknown territories. Yet for centuries, we've been told a story that migration is abnormal—a crisis, a disruption to the natural order. This narrative has shaped our borders, our policies, and even our scientific understanding of ourselves. But what if this fundamental assumption is wrong? What if movement, rather than stasis, is the defining characteristic of life on Earth? From the taxonomies of Carl Linnaeus that categorized humans into fixed racial groups to the border walls of today, powerful institutions have worked to keep people in their "proper places." These efforts have had profound and often devastating consequences. By tracing how migration has been misunderstood across centuries and disciplines, we gain insight into today's heated debates about refugees, climate displacement, and national identity. Whether you're concerned about environmental change, interested in human origins, or simply trying to make sense of headlines about migration crises, this exploration offers a revolutionary perspective on one of humanity's most fundamental activities—one that may be essential for navigating our uncertain future.

Chapter 1: Ancient Migrations: Our Species' First Global Journey (200,000 BCE)

Human migration began with our origins as a species. Approximately 200,000 years ago, the first anatomically modern humans appeared in Africa. These early Homo sapiens weren't content to stay in one place. Between 70,000 and 50,000 years ago, small groups began venturing beyond Africa, embarking on what scientists now call the "Recent Out of Africa" migration. This wasn't a single, organized movement but rather a series of journeys spanning countless generations as small bands ventured into unknown territories. What drove these ancient travelers? Climate fluctuations played a crucial role. During periods of warming, the Sahara briefly transformed into grasslands with lakes and rivers, creating corridors through once-inhospitable terrain. Later, during ice ages, sea levels dropped by hundreds of feet, exposing land bridges between continents. The most famous of these, Beringia, connected Siberia to Alaska, enabling the peopling of the Americas. These environmental changes created both opportunities and pressures for movement, as groups followed game animals, sought water sources, or fled deteriorating conditions. The archaeological record reveals the remarkable adaptability of these migrants. As they moved into new environments, they developed technologies suited to local conditions—from specialized hunting tools in the mammoth steppes of Europe to fishing equipment along coastal routes. Their bodies adapted too, with genetic changes emerging over generations. Those who ventured into higher latitudes evolved lighter skin to synthesize vitamin D from limited sunlight. Groups settling at high altitudes developed adaptations for low-oxygen environments. These biological changes occurred gradually over thousands of years, creating the diversity we see in human populations today. What's particularly striking about these ancient migrations is their success despite overwhelming obstacles. Without maps, compasses, or knowledge of what lay ahead, our ancestors navigated vast oceans, crossed scorching deserts, and scaled forbidding mountain ranges. They accomplished these feats without modern technology or understanding of geography, relying instead on observation, oral tradition, and remarkable resilience. As geneticist Svante Pääbo noted, "No other mammal moves around like we do. We jump borders. We push into new territory even when we have resources where we are... There's a kind of madness to it." This ancient pattern of movement established migration as fundamental to human experience—not an exception but the rule. By the time European explorers began circumnavigating the globe in the 15th century, humans had already reached virtually every habitable corner of the planet through countless migrations. This deep history of movement would be forgotten or deliberately obscured in later centuries, as scientists and politicians constructed theories portraying humans as naturally sedentary. But the archaeological and genetic evidence tells a different story: we have always been a species on the move, with migration as our defining characteristic.

Chapter 2: Scientific Racism: How Taxonomy Created Biological Borders (1700s-1800s)

By the 18th century, European naturalists began developing classification systems that fundamentally misunderstood migration's role in nature. Carl Linnaeus, the Swedish botanist who created modern taxonomy, established a system that categorized species according to their geographic origins. His approach assumed that plants, animals, and even human populations belonged in fixed locations, with clear biological borders between them. This sedentary worldview portrayed migration as unnatural and disruptive to a divinely ordered world. Linnaeus's taxonomy went beyond simply naming species. In his 1758 work "Systema Naturae," he divided humans into distinct categories based on continental origin: Homo sapiens europaeus (white Europeans), Homo sapiens asiaticus (yellow Asians), Homo sapiens americanus (red Americans), and Homo sapiens afer (black Africans). Each group was assigned not just physical traits but moral and intellectual characteristics. Europeans were described as "inventive" and "governed by laws," while Africans were labeled "lazy" and "governed by caprice." This classification system provided scientific justification for colonialism and racial hierarchies by suggesting that peoples had evolved separately and belonged in their respective geographic regions. The 19th century saw these ideas further entrenched through the work of scientists like Louis Agassiz at Harvard, who proclaimed that "the several races of men... are well marked and distinct." Even as Charles Darwin's theory of evolution suggested a common origin for humanity, scientists continued to emphasize differences rather than connections. Darwin's book "The Descent of Man," which argued against the concept of distinct human subspecies, was largely ignored by the scientific establishment. His biographers would later call it "Darwin's greatest unread book." These scientific myths about migration had profound political consequences. In the early 20th century, Madison Grant and Henry Fairfield Osborn, influential American scientists, used these ideas to advocate for immigration restrictions. They argued that migrants would contaminate the nation with "inferior germplasm," leading to biological degradation. Grant's book "The Passing of the Great Race" became a bestseller and influenced the Johnson-Reed Act of 1924, which drastically reduced immigration to the United States. Adolf Hitler later wrote to Grant, calling his book "my bible." The sedentary paradigm extended to wildlife as well. Charles Elton, the "founding father" of animal ecology, portrayed migration as a form of population control that ended in death. His theories about "suicidal" lemming migrations, in which the rodents supposedly flung themselves off cliffs to reduce their numbers, captured the public imagination. A 1958 Disney documentary called "White Wilderness" staged footage of lemmings being pushed off a cliff, cementing this myth in popular culture. The truth—that lemmings don't commit mass suicide—wouldn't be widely known for decades. These scientific misconceptions about migration weren't simply academic errors. They formed the intellectual foundation for policies that treated migrants as biological threats rather than as participants in humanity's oldest and most natural pattern of behavior. As explorer Thor Heyerdahl observed, "Borders? I have never seen one. But I have heard they exist in the minds of some people."

Chapter 3: Fortress Mentality: Immigration Restrictions and Their Deadly Consequences (1920s-1940s)

The early 20th century witnessed the transformation of border myths into deadly policy. Between 1880 and 1920, more than 20 million immigrants arrived in the United States, primarily from southern and eastern Europe. This demographic shift alarmed scientific elites like Madison Grant, who headed the New York Zoological Society, and Henry Fairfield Osborn, president of the American Museum of Natural History. These influential men believed that immigrants carried inferior genetic material that would contaminate America's supposedly superior racial stock. Their concerns were fueled by new theories about biological inheritance. The rediscovery of Gregor Mendel's work on pea plants and August Weismann's experiments with mice suggested that inherited traits passed unchanged through generations. This "Weismannism" implied that intelligence, moral character, and other qualities were fixed biological gifts, not qualities that could be nurtured through education or improved conditions. If immigrants with "inferior" traits reproduced with native-born Americans, they would permanently contaminate the population. The scientific establishment mobilized to restrict immigration. In 1921, the Second International Congress of Eugenics was held at the American Museum of Natural History, with exhibits showing the "scientific urgency" of ending immigration and race mixing. Grant and Osborn lobbied Congress for restrictive laws, testifying that newcomers were genetically inferior. Their campaign culminated in the Johnson-Reed Act of 1924, which drastically reduced immigration from southern and eastern Europe and barred most Asian immigrants entirely. President Calvin Coolidge, who signed the bill, had written that "biological laws" showed that "certain divergent people will not mix or blend." The consequences were tragic. When Jewish refugees attempted to flee Nazi Germany in the 1930s, the United States largely refused to admit them, citing the immigration quotas that Grant and Osborn had championed. In February 1939, a bipartisan bill to grant twenty thousand Jewish children asylum was killed in Congress. One opponent testified that twenty thousand "charming children would all too soon grow into 20,000 ugly adults." Months later, the ocean liner SS St. Louis, carrying more than nine hundred Jewish refugees, was turned away from American ports. More than 250 of those passengers would later perish in the Holocaust. The irony is that even as these policies were being implemented, the scientific claims on which they were based were falling apart. When Harvard anthropologist Harry Shapiro traveled to Pitcairn Island to study the effects of racial mixing, he found no evidence of degeneration. The islanders were "physically robust, suffered few diseases, exhibited generally average intelligence, and bore plenty of healthy babies." Franz Boas, studying immigrants and their children, found that physical characteristics changed within a single generation, contradicting the idea of fixed racial types. The fortress mentality of this era established patterns that continue to shape migration policy today. It transformed borders from relatively porous boundaries into heavily policed barriers and reframed migration from a natural human activity into a threat requiring military response. Most importantly, it demonstrated how scientific theories about human immobility could be weaponized with deadly effect. The echoes of these policies would continue to reverberate through subsequent decades, as new justifications for restricting migration emerged to replace the discredited theories of scientific racism.

Chapter 4: Population Panic: Environmental Arguments Against Human Movement (1960s-1980s)

By the 1960s, a new justification for restricting migration had emerged: environmental concerns about population growth. Paul Ehrlich's 1968 bestseller "The Population Bomb" warned that unchecked human reproduction would lead to mass starvation and societal collapse. Opening with a dramatic scene of overcrowding in Delhi, India, Ehrlich painted a picture of a world overwhelmed by too many people consuming too few resources. "The battle to feed all of humanity is over," he declared. "In the 1970s and 1980s hundreds of millions of people will starve to death." Though Ehrlich didn't initially focus on immigration, population control advocates quickly made the connection. Organizations like Zero Population Growth (ZPG) argued that even if Americans limited their family size, immigration would undermine these efforts. John Tanton, an ophthalmologist from Michigan who led ZPG's immigration committee, became particularly influential in this movement. In 1979, he founded the Federation for American Immigration Reform (FAIR), explicitly linking environmental concerns with anti-immigration policy. Tanton built a network of organizations dedicated to restricting immigration, including the Center for Immigration Studies and NumbersUSA. He cultivated relationships with both liberal environmentalists and conservative nationalists, framing immigration restriction as necessary for environmental sustainability. "We're not anti-immigrant," he would say, "just as someone on a diet is not anti-food." This environmental justification gave the anti-immigration movement a veneer of scientific legitimacy and moral urgency that appealed across the political spectrum. The environmental arguments against migration gained further momentum in the 1970s with the publication of "The Limits to Growth," a report commissioned by the Club of Rome that used computer models to predict resource depletion and environmental collapse. The report didn't directly address migration, but its warnings about exceeding Earth's carrying capacity were easily adapted to anti-immigration rhetoric. Garrett Hardin, an ecologist at the University of California, Santa Barbara, explicitly made this connection in his influential 1974 essay "Lifeboat Ethics," arguing that wealthy nations should close their borders to migrants just as a lifeboat must refuse additional passengers to avoid sinking. By the late 1970s, however, cracks appeared in this coalition. Revelations about forced sterilization programs in India, funded by Western population control advocates, horrified many liberals. When Tanton's private correspondence revealed explicitly racist views, many environmentalists distanced themselves from the anti-immigration movement. A bitter fight erupted within the Sierra Club over whether to adopt an anti-immigration stance, ultimately resulting in the organization rejecting Tanton's position. Despite these setbacks, the environmental justification for restricting migration had established deep roots. The idea that human movement threatens ecological stability continues to influence policy debates, even as the apocalyptic predictions of Ehrlich and others failed to materialize. The population panic of the 1960s and 70s demonstrated how environmental concerns could be weaponized against migrants, just as racial science had been in earlier decades. It also revealed how deeply the sedentary paradigm had penetrated even progressive movements, with many environmentalists assuming that keeping people in their "proper places" was necessary for planetary health.

Chapter 5: DNA Revolution: Discovering Our Migratory Nature (1980s-2000s)

The 1980s marked the beginning of a scientific revolution that would fundamentally challenge centuries of thinking about human migration. In 1987, researchers at the University of California, Berkeley—Rebecca Cann, Mark Stoneking, and Allan Wilson—published a groundbreaking study analyzing mitochondrial DNA from 147 women of diverse backgrounds. Their findings shocked the scientific community: all humans shared a common ancestor who lived in Africa just 200,000 years ago, a figure they poetically dubbed "Mitochondrial Eve." This discovery directly contradicted established theories, particularly Carleton Coon's influential 1962 book "The Origin of Races," which claimed that human races had evolved separately on different continents for over a million years. The DNA evidence suggested instead that humans had migrated out of Africa relatively recently and had not been isolated long enough to develop into separate subspecies. The variations between human populations that had been used to justify racial hierarchies for centuries turned out to be literally skin deep. Initially, many scientists resisted these findings. Critics complained that the researchers "simply didn't have the training" to make such claims. But as genetic evidence accumulated through the 1990s, the "Recent Out of Africa" theory gained acceptance. Population geneticist Luigi Luca Cavalli-Sforza incorporated DNA evidence with linguistic, archaeological, and anthropological data to map human migrations across the globe, confirming our African origins and subsequent worldwide dispersal. The Human Genome Project, completed in 2003, delivered another surprise. Humans have only about 20,000 genes—roughly the same number as a nematode worm and far fewer than the 100,000 scientists had expected. This limited genetic toolkit meant that the vast differences scientists had attributed to race couldn't possibly be encoded in our DNA. President Bill Clinton announced that humans are "99.9 percent the same, regardless of race," undermining centuries of scientific racism. Perhaps most revolutionary was the discovery that human migration hadn't stopped after the initial exodus from Africa. New techniques for extracting DNA from ancient bones, particularly from the dense petrous bone of the inner ear, revealed a history of continuous movement and mixing. Europeans, for instance, descended from at least three distinct populations that had migrated into the region and interbred. The tree-like model of human populations branching apart was replaced by a more accurate image of branches that repeatedly merge back together. These genetic discoveries transformed our understanding of human history and identity. They revealed that migration is not an anomaly or a modern crisis but the defining feature of our species—so much so that we might more accurately be called Homo migratio rather than Homo sapiens. As geneticist Spencer Wells put it, "We are all migrants on a journey that began in a small corner of Africa. The differences between us are, in a very literal sense, skin deep." This new scientific understanding directly contradicted the sedentary paradigm that had dominated for centuries, suggesting that policies restricting migration work against our fundamental nature as a species.

Chapter 6: Climate Displacement: Migration as Adaptation in a Warming World (Present-Future)

Today, we stand at the threshold of what may become the next great migration in human history. Climate change is already forcing both humans and wildlife to move. A comprehensive study of 4,000 species found that they are moving toward the poles at an average rate of 3.8 miles per decade. Coral reefs are shifting poleward as oceans warm. Alpine plants are climbing higher up mountain slopes. These movements aren't anomalies—they represent natural adaptations to changing environmental conditions. Humans, too, are on the move. Between 2008 and 2014, an estimated 184 million people were displaced by sudden-onset disasters like floods and storms. In regions like the "Dry Corridor" of Central America, persistent drought has contributed to migration northward. Rising seas threaten to make low-lying coastal areas and island nations uninhabitable. The World Bank estimates that by 2050, more than 140 million people may be forced to move within their countries due to climate impacts. These movements are not temporary disruptions to a stable world—they represent the beginning of a fundamental reorganization of where life can thrive on our planet. Yet our political and legal systems remain trapped in the outdated sedentary paradigm. International refugee law, created after World War II, recognizes persecution but not environmental degradation as grounds for protection. Border walls and fences have proliferated, with more borders fortified today than at any time in history. These barriers are largely ineffective at stopping human movement but deadly in their consequences, forcing migrants into increasingly dangerous routes. Between 1993 and 2017, over 33,000 people died trying to migrate into Europe, many drowning in the Mediterranean Sea. The science of migration suggests a different approach. Studies show that migration is not a desperate last resort but an adaptive response to environmental change. Like other species, humans have evolved to move when conditions shift. Our bodies contain physiological adaptations acquired during our migratory history—from variations in skin pigmentation that evolved as we moved to different latitudes to genetic variants that help some populations digest milk or survive at high altitudes. These adaptations demonstrate how migration has been essential to our survival as a species. Forward-thinking communities are beginning to incorporate migration into climate adaptation strategies. In Bangladesh, where rising sea levels threaten coastal areas, the government has developed programs to help people move inland and acquire skills for urban employment. In the Horn of Africa, international agencies support pastoralists in adapting their traditional migration routes to changing rainfall patterns. These approaches recognize migration as a solution rather than a problem—a way for people to actively respond to environmental challenges rather than passively accepting their fate. As climate change accelerates, the question is not whether migration will occur, but how we will respond to this fundamental aspect of life on a dynamic planet. Will we continue to build walls and criminalize movement, or will we develop systems that recognize migration as an essential adaptation strategy? The choices we make today will determine whether the coming migrations unfold as humanitarian disasters or as successful adaptations to our changing world.

Chapter 7: Breaking Barriers: Toward Safe Passage in a Mobile World

The militarized borders that define our world today are neither natural nor inevitable. Throughout most of human history, kingdoms and empires had blurry edges, with cultures and peoples gradually shading from one to the next. Even the highly contested border between the United States and Mexico remained largely permeable until recent decades. The rigid, fortified borders we now take for granted are historical anomalies, products of the same flawed thinking that categorized humans into fixed, immutable races. These barriers exact a terrible human cost. In the Mediterranean, one migrant dies for every fifty-one who successfully reach Europe. Along the U.S.-Mexico border, migrants die of dehydration in the desert or drown crossing the Rio Grande. Those who survive face detention, family separation, and deportation to places where they may face violence or extreme hardship. Children are particularly vulnerable—over one hundred countries around the world detain migrant children, despite overwhelming evidence of the psychological harm this causes. Yet there are alternatives emerging. Conservation biologists have pioneered the creation of wildlife corridors that allow animals to move safely across fragmented landscapes. The Yellowstone to Yukon Initiative, for example, has created a protected pathway spanning five hundred thousand square miles across which bears, wolves, and other species can travel. Similar approaches could inform human migration policy, creating safe, legal pathways for people on the move. Some regions are already experimenting with more humane approaches. The African Union's Protocol on Free Movement of Persons aims to gradually eliminate barriers to migration within the continent. The Economic Community of West African States (ECOWAS) has implemented a free movement regime that allows citizens to travel between member states without visas. These initiatives recognize that migration is not a problem to be solved but a reality to be managed—and potentially a source of economic and cultural vitality. Technology is transforming migration management as well. Digital identity systems help refugees maintain access to financial services and education across borders. Mobile apps connect migrants with healthcare, legal advice, and community support. Satellite imagery and climate modeling allow for better prediction of environmental changes that might trigger migration, enabling more proactive responses. These innovations don't eliminate the challenges of migration, but they make them more manageable. As we face a future of accelerating climate change and environmental disruption, we have a choice. We can continue to cling to the myth of a sedentary world, building ever higher walls and accepting the deaths of thousands as the price of maintaining this illusion. Or we can embrace the reality that migration is not a crisis to be solved but a constant companion of life on Earth—including human life. By creating systems that acknowledge and accommodate our migratory nature, we can transform migration from a source of suffering and conflict into a natural adaptation to our changing world. The barriers we've built are recent inventions. They can be reimagined for a future where safe passage becomes the norm, not the exception.

Summary

Throughout human history, our understanding of migration has been distorted by a fundamental misconception: that staying put is natural and moving is aberrant. This sedentary bias has shaped everything from Linnaeus's racial taxonomies to today's border walls. Scientists from the 18th century onward constructed elaborate theories positioning humans as naturally fixed in place, despite mounting evidence to the contrary. These theories weren't merely academic—they justified colonialism, inspired immigration restrictions that condemned refugees to death, and continue to influence policies that make migration unnecessarily dangerous. The DNA revolution of recent decades has thoroughly debunked these notions, revealing humans as a fundamentally migratory species whose history is characterized by continuous movement and mixing. As climate change forces both humans and wildlife to shift their ranges, we face a critical choice about how to respond. We can continue treating migration as a crisis to be suppressed through walls, detention, and deportation—policies that cause immense suffering without actually stopping movement. Or we can recognize migration as an adaptive response to environmental change and create systems that make it safer and more orderly. This might include international agreements that recognize climate displacement, legal pathways for migration that reduce dangerous irregular journeys, and infrastructure designed to facilitate rather than impede movement. By embracing our migratory nature rather than denying it, we can transform one of humanity's oldest behaviors from a source of conflict into a solution for navigating our rapidly changing world.

About Author

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Sonia Shah

Sonia Shah is a science journalist and prize-winning author. Her writing on science, politics, and human rights has appeared in the New York Times, the Wall Street Journal, Foreign Affairs, Scientific American and elsewhere. Her work has been featured on RadioLab, Fresh Air, and TED, where her talk, “Three Reasons We Still Haven’t Gotten Rid of Malaria” has been viewed by over 1,000,000 people around the world. Her 2010 book, The Fever, which was called a “tour-de-force history of malaria” (New York Times), “rollicking” (Time), and “brilliant” (Wall Street Journal) was long-listed for the Royal Society’s Winton Prize. Her new book, Pandemic: Tracking Contagions from Cholera to Ebola and Beyond, is forthcoming from Sarah Crichton Books/Farrar, Straus & Giroux in February 2016.

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