The Next Great Migration: The Beauty and Terror of Life on the Move

by Sonia Shah

What happened on Kaibab and St. Matthew recalled the warnings of the eighteenth-century cleric Thomas Robert Malthus. Malthus had pointed out that aiding the poor with food and clothing, as England’s Poor Laws required and which most people viewed as beneficial charity, circumvented nature’s checks on human population growth. “We cannot, in the nature of things, assist the poor, in any way,” Malthus wrote in 1798, “without enabling them to rear up to manhood a greater number of their children.” Progress against poverty, disease, and hunger would result in an exponentially growing human population, Malthus warned, whose appetites would regularly outstrip the food supply, creating a permanent state of conflict and scarcity.

Influential thinkers condemned Malthus as an alarmist. The nineteenth-century philosopher Friedrich Engels called his theory “hideous blasphemy against nature and mankind.”

Scientists started resurrecting Malthusian concerns in a spate of popular books.

William Vogt, who’d written the foreword to John James Audubon’s illustrated classic Birds of America, wrote a best-selling book on the topic called The Road to Survival in 1948.

“Every argument, every concept, every recommendation” in Vogt’s book, notes the historian Allan Chase, became “integral to the conventional wisdom of the post-Hiroshima generation of educated Americans.” The Reader’s Digest, a publication with sales second only to the Bible, reprinted a condensed version of Vogt’s book. Between 1956 and 1973, seventeen out of twenty-eight general biology textbooks included a version of Leopold’s account of the collapse of the deer in Kaibab.

Malthus’s predictions never made sense to me and never panned out. They were poorly analyzed and insufficiently discussed in the 69s and 70s.

Paul Ehrlich

Dal Lake

“Uncontrollable aggressiveness” resulted from crowding, the zoologist and TV host Desmond Morris wrote. It had been “proved conclusively with laboratory experiments.” The journalist Tom Wolfe compared crowds of New Yorkers “running around, dodging, blinking their eyes, making a sound like a pen full of starlings or rats.” The critic and philosopher Lewis Mumford wrote of the “ugly barbarization” of humans due to “sheer physical congestion,” which had been “partly confirmed” by Calhoun’s experiments in rats. The “freedom to breed,” Hardin argued, had become “intolerable.”

Scientists started to refer to human population growth10 not as the happy outcome of prosperity and improved health but as a silent killer that would violently erupt.

disdained voluntary family planning programs, which left it up

Controversially, in 2000 the Canadian psychologist John Philippe Rushton would explicitly apply r/K selection theory to human racial groups,16 arguing that black people were r-strategists, “Orientals” K-strategists, and white people in between.

The Population Bomb, the Sierra Club’s David Brower similarly presumed fixed r/K–like differences between people who lived in different places. “Countries are divided rather neatly into two groups,”18 Brower wrote. “Those with rapid growth rates, and those with relatively slow growth rates.” The fast growers, he wrote, were “not industrialized, tend to have inefficient agriculture, very small gross national products, high illiteracy rates and related problems.” The slow growers, presumably, were just the opposite. Ehrlich’s fellow neo-Malthusian scientists,19 such as Kingsley Davis, explicitly called for an end to immigration. According

The journalist Joyce Maynard remembers the “rush of dread” she felt22 while reading The Population Bomb. “Not personal individual fear,” she explained, “but end-of-the-world fear, that by the time we were our parents’ age we would be sardine-packed and tethered to our gas masks in a skyless cloud of smog.”

twentieth century.

The University of Pennsylvania anthropologist Carleton Coon, president of the American Association of Physical Anthropologists, went further. He claimed that there’d been no prehistoric migrations at all.9

Populations of now-extinct Homo erectus had dispersed across the planet and slowly evolved into modern Homo sapiens independently

Scientific belief in biologically distinct racial groups10 remained widespread.

In 1950, in the wake of revelations of Nazi crimes in the name of biological distinctions between peoples, a top agency of the newly formed United Nations issued a statement officially condemning race as an ideological concept, with no basis in biology. But when the agency asked leading scientists to sign on to the statement, they’d balked. Even those sympathetic to the cause of antiracism were reluctant.

Influential scientists lauded the book. Coon’s theory, while “highly speculative,” the anthropologist Frederick Hulse noted, was “really comprehensive.” In the pages of Science magazine, the Harvard evolutionary biologist Ernst Mayr lauded Coon’s book

If groups of Homo erectus had indeed been marooned on their own continents and evolved separately from each other, they’d have been unlikely to all evolve into the exact same species, as Coon’s theory suggested. More likely they’d diverge into five different ones.

That’s not what this mitochondrial DNA showed. According to the geneticists’ analysis, the 147 women of different racial and continental backgrounds had shared common ancestors as recently as two hundred thousand years ago. If true, the long period of isolation that scientists had presumed for centuries didn’t exist. The peoples of the world had emerged from a common ancestor so recently that they had had far less time to differentiate than previously believed.

In just a few hundred thousand years, people had catapulted themselves into every last corner of the planet.

“Mitochondrial Eve.”

Research by scientists such as the population geneticist Luigi Luca Cavalli-Sforza supported the migratory history suggested by Mitochondrial Eve.

The World Council of Indigenous Peoples dubbed Cavalli-Sforza’s work the “Vampire Project.” The Third World Network, an NGO, called it “totally unethical and a moral outrage.”

Cavalli-Sforza Cavalli-Sforza initiated a new field of research by combining the concrete findings of demography with a newly available analysis of blood groups in an actual human population. He also studied the connections between migration patterns and blood groups. Writing in the mid-1960s with another genetics student of Ronald A. Fisher, Anthony W. F. Edwards, FRS, Cavalli-Sforza pioneered statistical methods for estimating evolutionary trees (phylogenies). Edwards and Cavalli-Sforza wrote about trees of populations within the human species, where genetic differences are affected both by treelike patterns of historical separation of populations and by spread of genes among populations by migration and admixture. Many of these influential and fundamental early papers were reprinted in 2018 in a volume focusing on A. W. F. Edwards, and dedicated to Cavalli-Sforza and Ian Hacking.[2] In later papers, Cavalli-Sforza has written about the effects of both divergence and migration on human gene frequencies. While Cavalli-Sforza is best known for his work in genetics, he also, in collaboration with Marcus Feldman and others, initiated the sub-discipline of cultural anthropology known alternatively as coevolution, gene-culture coevolution, cultural transmission theory or dual inheritance theory. The publication Cultural Transmission and Evolution: A Quantitative Approach (1981) made use of models from population genetics and infectious disease epidemiology to investigate the transmission of culturally transmitted units. This line of inquiry initiated research into the correlation of patterns of genetic and cultural dispersion.

David Reich,

But already paleogeneticists such as Sweden’s Svante Pääbo and Harvard’s David Reich, among others, have revealed a backstory of ancient migrations that is far more complex than what Cavalli-Sforza and others extrapolated from modern-day DNA.

About 2 percent of the DNA in modern-day peoples in Europe and Asia traces back to the migratory collision with Neanderthals; and around that proportion of DNA in people now living in New Guinea and Australia traces back to the Denisovans, a group of ancient humans discovered through genetic analyses.