Today more than ever, food has also become a lens through which we engage with the world sensually, emotionally, ethically, politically, and personally.

In his economic masterwork The Wealth of Nations, the great Scottish economist Adam Smith reveals himself to be a deep admirer of Irish poor folk. Or, more specifically, their preferred food, potatoes.

“The chairmen, porters, and coal-heavers in London, and those unfortunate women who live by prostitution, the strongest men and the most beautiful women perhaps in the British dominions, are said to be, the greater part of them, from the lowest rank of people in Ireland, who are generally fed with this root,” Smith wrote. “No food can afford a more decisive proof of its nourishing quality, or of its being peculiarly suitable to the health of the human constitution.”

Smith had struck on a connection little recognized even today: that improved labor productivity, surging population, and outmigration were thanks to the potato.

This phenomenon wasn’t confined to Ireland. As The Wealth of Nations went to press, across Europe, the potato was upending the continent’s deep demographic and societal decline. Over the next couple centuries, that reversal turned into a revival. As the late historian William H. McNeill argues, the surge in European population made possible by the potato “permitted a handful of European nations to assert domination over most of the world between 1750 and 1950.”

Europe in decline

In hindsight, the rise of Europe—and, more broadly, the West—seems inevitable. It wasn’t. In fact, a glance at 1600s Europe makes this ascension look downright dubious.

During its civilizational heyday between the ninth and 14th centuries, Europe’s population doubled. But by the 1300s, the continent had more people than its land and soil could feed—a state worsened by the arrival of the Black Death. Though its population began to recover ever so slightly in the 1500s, the continent still relied on grains that had developed little since the Neolithic Era and that were therefore prone to failure. Famine was frequent and rampant. Scarce land spurred wars that starved even more people. Peasants sometimes killed their infants rather than struggle to feed them.

In short, by the 1600s, the continent was already plunged deep into demographic decline. “Europe could not, with the agriculture it possessed, feed her lower classes and also support the high-flown schemes of her upper classes,” writes eminent historian Alfred Crosby in Germs, Seeds and Animals. Precedent suggests that this should have spelled long-term doom for European civilization.

Then down from the Andes, ferried across the Atlantic in Spanish galleons, came ashore the potato.

From love-drug to miracle crop

The tuber’s story starts more than 4,000 years ago in the Andes, when locals in the highest mountain plains domesticated wild potatoes, selecting for traits that let them survive the evening frosts that killed other plants. Starting around 100 CE, the pioneering of underground freezers, a potato-based tax system, and enslavement of peasant farmers fueled the rise of the Incan empire, writes McNeill.

That civilization ended when Spaniards invaded in the mid-1500s; the potato-based system of coercion didn’t. The conquistadors instead used the potato surplus to feed slaves mining silver. The resulting silver glut funded a century of Spanish imperialism.

When brought back to Europe, potatoes weren’t an easy sell at first. Unlike the other important New World crop, maize, their appeal wasn’t immediately obvious. At first, the European upper class hailed potatoes as aphrodisiacs. (This explains why Shakespeare’s perpetually horny buffoon Falstaff bellows, “Let the sky rain potatoes!”)

Peasants racked by famine, though, were quick to find the tuber’s true virtues. As Smith correctly noted, potatoes were a far better energy source than Europe’s existing staples, yielding between two and four times more calories per acre. They were far cheaper than bread. Unlike grains, potatoes came from the ground plate-ready, saving labor. One needed little land and practically no capital to farm them.

Potatoes were also vastly more nutritious. A single acre planted with potatoes and the milk of one cow could feed an entire family, providing the all necessary vitamins and micronutrients for a healthy diet. They’re rich enough in vitamin C that they helped end rampant scurvy throughout the continent.

The botanical knack of Andean farmers millennia earlier proved valuable in northern Europe, as potatoes thrived in colder climes than staple grains could tolerate. Since potatoes could be cultivated on the large tracts of grain plots allowed to fallow each year—a form of weed control—potato production complemented grain output. Extra potatoes could be used as fodder for pigs and other livestock, which put protein-rich meat within reach of peasants who could previously afford little or none. That also meant more manure and wider availability of livestock for farming, boosting agricultural output all the more.

War and potatoes

It’s probably no coincidence that the man who once said “an army travels on its stomach” was Europe’s first head-of-state tater-booster. So effective was the crop that Frederick the Great of Prussia ordered his government to distribute free seed potatoes and planting instructions throughout his kingdom. That proved smart: Prussian peasants survived French, Austrian, and Russian invasions in unprecedented numbers.

Those invaders soon caught on, encouraging their own plebeians to grow the crop. To this end, Marie Antoinette once sported a potato-flower headdress at a court ball to extol the tuber’s virtues, as McNeill recounts.

The crop certainly did make it easier to staff and feed vast armies. For instance, in the late 1770s, potatoes fed both sides fighting the War of Bavarian Succession, which ended when Bohemia ran out of potatoes.

The Potato War, as it’s sometimes known, doesn’t reflect the potato’s broader promotion of peace, however. The potato’s spread caused a sharp fall in the incidence of conflict, as three economists—the University of Colorado’s Murat Iyigun, Nathan Nunn of Harvard, and Nancy Qian at Northwestern’s Kellogg School of Management—document in a new working paper (registration required) published by the National Bureau of Economic Research.

That may have been because people mainly fought over land, and land’s prime value came from agriculture. Increased productivity would have effectively driven down land values, lowering incentives to shed blood fighting over it, they argue. If higher productivity pushed up real wages for peasant farmers, as you’d expect, the opportunity cost of rioting would climb—as it would, too, for rulers who taxed labor for revenue.

Wars still broke out, of course. But the potato’s spread dramatically limited the destructive consequences of conflict, argues McNeill. The costs and difficulty of transporting soldiers’ rations meant that armies simply stole food from peasants wherever they were operating—which is why long military campaigns usually are accompanied by mass peasant starvation. Potatoes changed that. Fleeing peasants could bundle them up much more easily than grain. And foraging soldiers generally preferred raiding above-ground supplies to digging up potatoes.

Of course, the dependence of so many of Europe’s poor on the potato created new vulnerabilities too—most notoriously, to the potato blight that killed a million people and sent a million more emigrating from Ireland in the late 1840s, many of them to the US.

Dodging a demographic crisis

As Crosby argues, the potato helped stave off the demographic crisis that seemed so certain in the 1600s, from which it would have taken generations to recover. Instead, the potato helped prime the economy with the wealth and manpower needed to fuel the Industrial Revolution.

It’s often assumed that Europe’s rise resulted from the Industrial Revolution and, to a lesser extent, the leap in scientific farming known as the Agricultural Revolution. However, Europe’s surprising revival predates both—and the potato has much to do with that.

With Europe’s food supply suddenly more abundant, nutritious, and secure, peasants lived longer and had bigger families. The population leapt from 126 million in 1750 to 300 million by 1900 (and that’s not counting mass emigration). When the population grew bigger than the number needed to toil in the fields, this time peasants didn’t die of mass starvation. They simply moved to the cities. The potato accounts for around a quarter of the population growth and as much as a third of increased urbanization between 1700 and 1900, according to an earlier paper (pdf) by Qian and Nunn.

It’s thanks to these trends, argues McNeill, that northern Europe’s industrial transformation proceeded as swiftly as it did. “It is certain that without potatoes, Germany could not have become the leading industrial and military power of Europe after 1848, and no less certain that Russia could not have loomed so threateningly on Germany’s eastern border after 1891.”

The swelling population also staffed imperial militaries that forced distant peoples to buy European goods and produce raw materials for its industries. The continent’s most world-altering export, however, was people.

The Caucasian tsunami and the quest for surplus

Europe’s potato-fueled population boom warped the planet in other lasting ways. Between 1820 and 1930, some 50 million Europeans—about equal to one-fifth of its population as of 1820—migrated to the New World countries. The “Caucasian tsunami” that left Europe between the 1840s and World War I was “the greatest wave of humanity ever to cross oceans and probably the greatest that ever will cross oceans,” writes Crosby in Ecological Imperialism.

These civilians were the shock troops of the new—and, largely, permanent—global regime. Thanks to the concatenating population explosions due in no small part to the potato, whites gained 30 million square kilometers of land, most of which they still control. The area of the world settled by Europeans was around 22% in 1750; two centuries later, it stood at 36%.

In an inversion of the potato miracle that helped make their migration possible, European immigrants thrived through growing Old World grains in their new terrain. The resulting plenty boosted birth rates to among the highest in recorded history. Through trade and imperialism, those surpluses fed and fueled Europe’s Industrial Revolution and, eventually, the industrial revolution in the US that led America to seize the mantle of Western global dominance.

This helps explain why the potato is no longer the world’s biggest crop—in fact, it hasn’t been since 1965. But its legacy endures. The Caucasian tsunami surpluses that once fed industrializing Europe now feed the world.