“Migration is the planet’s connective tissue”

Movement has shaped Earth as we know it but we’re only now starting to understand, says science journalist Sonia Shah

When people start moving, we call it a “migrant crisis”. It’s reflexive. And it happens regardless of whether host societies have the capacity to absorb migrants or whether migrants themselves and the societies they enter and leave would be better or worse off because of their movements.

In part, that’s because we’ve long misunderstood the scale and meaning of movement on our shared planet.

In the 18th century, the founder of modern taxonomy, Carl Linnaeus, characterised the natural world as essentially still. Each animal belonged where it was found and hadn’t moved from one place to another; each human population was similarly fixed in place on the planet. Thanks to Linnaean taxonomy, we name things based on their fixed places and where they “belong”: the Canadian goose, the Japanese maple. We use animals to stand in for places, as if they are one and the same: the camel stands in for the Middle East; the kangaroo for Australia – as if they have been there from time immemorial and could never shift.

Linnaeus decided that people who lived in different continents had been so biologically isolated from each other that they were separate subspecies, creating a human taxonomy which separated people by colour, continent, and his sense of their morals. He relied heavily on folklore and myth about tailed men and African women with bizarre genital growths (his taxonomy was famously based on sexual characteristics, which is why it was controversial and called “loathsome harlotry”). Elevating the degree of differentiation between us obscured our common origin and our shared migratory history. Nevertheless, his ideas formed the foundation for modern ideas about racial difference, which are used to justify anti-migrant policies to this day.

Ancient DNA shows that we’ve continuously migrated

We’ve minimised the role and scope of migration ever since. For example, Europeans refused to believe Polynesian people’s story of prehistoric migrations to the Pacific Islands by canoe from Asia. They thought that purposeful long-distance movements were only possible with modern Western technology. In the 1940s, the Norwegian explorer Thor Heyerdahl theorised that the only way people could have gotten to the remote Pacific islands was by floating there on a raft from Peru. He was so convinced of his theory that he tried it himself on the Kon Tiki raft, which became a popular movie and book. Up until the 1960s, top geographers said that migration has played such a minor role in human history that the people who lived on different continents had actually evolved there.

Today’s policymakers similarly underestimated the pace of human movements when they claimed they could arrest the spread of novel coronavirus by closing the borders, seemingly unaware that seven million people had already left the city of Wuhan before it was locked down. It was only after the borders slammed shut that it became clear that our movement patterns made even our most stringent efforts to stop the microbe’s dispersal futile.

Our underestimation of the scope of migration has been coupled with an outsized focus on migration’s disruptive effects. We call the movement of wild species into novel habitats “invasions” of unwanted “aliens,” even though according to a general rule in invasion biology, only 10 per cent of alien species establish themselves in new habitats and only 10 per cent of those are likely to cause unwanted harm to economies, ecosystems or human health.

Human migrants are blamed for all manner of social ills, from the spread of crime and terror to disease. One result is that today, more borders are fortified with walls and fences than at any time in history.

But new findings made possible by advancements in genetics and navigation are upending conventional notions of migration as rare and disruptive, revealing migratory capacities more extensive and more deeply embedded in history and nature than ever before imagined.

Our capacity to co-operate across geographic barriers relies on the cultural connections forged by people on the move

Ancient DNA shows that we’ve continuously migrated. We didn’t just disperse out of Africa into an empty planet and then stop moving until modern times. We migrated out of Africa into Eurasia and then back again; we moved from Eurasia into South Asia; we migrated into the Americas and then back to Europe. Some of the most forbidding migrations, such as into the Tibetan plateau and the remote Pacific had been accomplished not just once but multiple times.

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A revolution in animal tracking thanks to GPS and solar technology has revealed that animal movements are much more expansive in scale and more complex and responsive than ever before imagined, too. The movements of mountain goats is shaped by the timing of volcanic eruptions, which they detect six hours before seismologists can. The flight paths of swans curve according to cold snaps, and could forecast outbreaks of avian influenza days before traditional methods of influenza surveillance. The creep of thousands of species toward the poles and into the heights tracks the shifting climate.

We live in a world on the move. And nature depends on our journeys. Ecosystems depend on the biological connections provided by wild species on the move. Over 90 per cent of the trees in rainforests, for example, rely on the movements of birds and other animals to disperse their seeds. Human mobility is fundamental to our biological resilience. Our capacity to co-operate across geographic barriers relies on the cultural connections forged by people on the move, injecting genetic and cultural diversity into otherwise insular societies.

Migration is the planet’s connective tissue. It’s not the crisis we reflexively imagine it to be. In a rapidly changing world, migration may be just the opposite: the solution.

Sonia Shah is the author of The Next Great Migration: The Story of Movement on a Changing Planet (Bloomsbury, £14.99)