Hundreds of thousands of years before the invention of the wheel, some unlucky hominin stepped on a loose rock or unstable log and—just before they cracked their skull—discovered that a round object reduces friction with the ground.

The inevitability of this moment of clarity explains the ancient ubiquity of rollers, which are simply logs put underneath heavy objects. The Egyptians and the Mesopotamians used them to build their pyramids and roll their heavy equipment, and the Polynesians to move the stone moai statues on Easter Island. But rollers aren’t terribly efficient, because they have to be replaced as they roll forward, and even if they’re pinned underneath, friction makes them horribly difficult to move. The solution—and the stroke of brilliance—was the axle. Yet despite the roller’s antiquity, it doesn’t appear that anyone, anywhere, discovered the wheel and axle until an ingenious potter approximately 6,000 years ago.

The oldest axle ever discovered is not on a wagon or cart, but instead on a potter’s wheel in Mesopotamia. These may seem like simple machines, but they’re the first evidence that anyone anywhere recognized the center of a spinning disk is stationary and used it to their mechanical advantage. It’s a completely ingenious observation and so novel that it’s unclear where the idea came from—perhaps from a bead spinning on string?—as it has no obvious corollary in nature. The pole is called an axle, and many scholars consider it the greatest mechanical insight in the history of humankind.

Yet there exists another great intellectual leap between the potter’s wheel and a set of wheels on a rolling object. The full wheel set appears to have first been invented by a mother or father potter, because the world’s oldest axles are made of clay, are about two inches long, and sit beneath rolling animal figurines.

The first wheeled vehicle, in other words, was a toy.

In July 1880, the archaeologist Désiré Charnay discovered the first pre‑Columbian wheel set in the Americas. It was on a small coyote figure mounted on four wheels, and Charnay found it in the tomb of an Aztec child buried south of Mexico City.

As Charnay presumes in his book The Ancient Cities of the New World, the toy was a memento of “a fond mother … who, ages gone by, buried [it] with her beloved child.”

The Aztec child lived thousands of years after the inventor in the high steppe but before the Europeans arrived with their wheels in the Americas, which suggests that in both the New and Old Worlds a mother or father potter independently invented the wheel and axle to make a toy.

The archaeologists I spoke with are hesitant to believe such a remarkable insight could have been made in the pursuit of something as frivolous as an object for play. The engineers, however, are not. Instead, they believe it would be far more remarkable if the first wheel and axles appeared on 500‑pound wagons. Small versions of inventions—modernly called models or prototypes—nearly always precede larger ones. They are far easier to build, take far less time, and allow an inventor to quickly discover potential problems and find solutions.

Yet as ingenious as this inventor was, their toy did not spark a societal revolution. The person who scaled it into a full‑size set of wheels a few hundred years later did. The full‑size wagon first appeared approximately 5,400 years ago, and it may be one of the the first inventions in history to go viral. Archaeologists have discovered full‑size carts from southern Iraq to Germany within a few hundred years of each other at a time when cultural barriers were particularly impermeable. The wagon, it seems, was irresistibly useful.

When I asked David Anthony, an anthropologist and the author of The Horse, the Wheel, and Language, what explains this viral growth, he believes part of the reason may be the wagon’s sheer size: “These were probably the biggest wooden machines anyone had ever seen,” he says. They would have been loud; they would have been slow. And they were powered by teams of oxen, which were by themselves some of the largest animals in the steppe.

The invention of the wagon was the prehistoric equivalent of Sputnik; it did not go unnoticed. Because the two oldest wheels archaeologists have found vary significantly in design—one has an axle fixed to the wheel as it does on a modern train, the other spins freely on the axle like on a modern car—Anthony suggests that at least some wagon builders copied what they saw from afar without being able to inspect it closely.

The invention and widespread adoption of the wagon had an immediate and dramatic effect on societies throughout the Middle East and Europe. It drastically increased a farmer’s productivity, and in doing so altered the landscape. Where once farms required teams of people to move the heavy loads of fertilizer, seeds, and crops, the wagon allowed for the possibility of a single‑family venture. Populations that were previously clustered around rivers exploded onto the productive but unexploited steppe. The wagon changed entire economies, lifestyles, wars, and even languages. “It would be difficult to exaggerate the social and economic importance of the first wheeled transport,” writes Anthony.

The wheel might have begun with a miniature, but the miniature didn’t change the world. The full‑size version did. And scaling a miniature wheel required its own genius. Anthony believes the full‑size wheel and axle may have required craftsmanship so delicate, it was impossible to build with stone tools and could only be made with the gouges and awls metallurgists had only recently begun to cast. Finally, it couldn’t have been made in stages, which means an individual built the first one.

The identity of the inventor of the first full‑size wheel has become a cliché representing the unknowable, but recent reconstructions of long‑dead languages have provided a powerful new piece of evidence that has brought scholars closer to the inventor than ever before.

Who made the first full‑size wheeled vehicle?

I’ll call him Kweklos—Kay for short—which paleolinguists believe is the word he may have used for “wheel.” In his language, kweklos originates from the verb “to turn,” meaning he referred to his invention very appropriately as “the turner.” And I’ll call Kay a him because the first known wagon driver is a man buried atop his wagon east of the Black Sea.

Kay was born roughly 5,400 years ago, a date that is well supported thanks to the popularity of Kay’s invention. Wagons and references to them explode in the archaeological record from the Middle East to Western Europe within a few generations of each other.

But if the when of Kay’s birth has largely been established, the where is the subject of a lively academic debate. Anthony tells me the wagon “spread so fast that it’s impossible to pinpoint a clear and obvious earliest date.” As of now, two full‑size wagon wheels tie for the oldest that archaeologists have found. One comes from a Slovenian bog in Ljubljana; the second comes from the remarkable Yamnayan culture grave just east of the Black Sea in the North Caucasus, Russia, where archaeologists found not only a wheel but an entire wagon complete with the skeleton of a thirtysomething man sitting atop it.

Archaeology is not the proper science for pinpointing the location of viral inventions. There are, however, linguistic reasons to suspect the Yamnayan man buried with his wagon may have lived close to where the invention occurred. Many paleolinguists now believe the Yamnaya spoke a language called Proto‑Indo‑European (PIE), and reconstructions of that long‑dead language suggest it’s the native language of the wheel’s inventor.

“The vocabulary for wheels shows that most of the words for wheels and axles were created by PIE speakers from their own verbs and nouns,” Anthony tells me. For example, the PIE word for “axle” (aks) derived from the PIE word for “shoulder,” which means PIE speakers used a word from their own language rather than a foreign one to refer to the wheel and wagon.

This fact is critical, because when cultures adopt foreign technology they typically adopt the originating culture’s terminology as well. When the Spanish brought the tobacco plant back from the Caribbean, for example, they kept the local Taino word tabako. Reconstructions of wheel vocabulary suggest—though do not prove—that Kay was a PIE‑speaking Yamnayan like the man buried with his wagon in the southwest corner of Russia.

Kay was a farmer and a herder. He had dogs, horses, and sheep, and perhaps wore some of the earliest wool clothing. He enjoyed mead, an alcoholic honey drink, and he raised cattle and drank their milk. He lived in a long house in a small farming community likely clustered near rivers.

Linguistic evidence suggests Kay worshipped a male sky god, sacrificed cows and horses in his honor, and lived in a village with respected chiefs and warriors. DNA of Yamnayans suggest Kay was likely to have had brown eyes, dark hair—though with an outside chance at red—and somewhat olive‑toned skin. The average height for Yamnayan men was approximately 5-foot-9, and he likely had a heavily muscled frame from years spent toiling in his field.

Many of Kay’s personal details are of course speculative, but one thing is certain: The builder of the first wagon was a genius at conception and craft. There is no other explanation. Scaling the toy into a full‑size wagon meant solving a host of engineering, design, and woodworking problems. Some scholars, including Anthony, believe it isn’t a coincidence that metallurgists first cast copper tools only a few generations before the first wagon. They believe the precise craftsmanship needed to construct a functional wheel and axle may have been impossible with stone tools.

The first and most critical component of the wheel, writes Steven Vogel, author of Why the Wheel Is Round, is the fit with the axle. Too tight and the wagon is hopelessly inefficient, too loose and the wheel wobbles and breaks apart. The problem would not have been revealed by the matchbox‑size wheel and axles, nor would models have required the proper ratio between the diameter and length of the axle. Too thick and the axle creates too much friction; too thin and it breaks under strain of the load.

Then there would have been the matter of the wheel itself, which is a deceivingly complex device. If Kay had cut a fallen tree salami‑style for his wheel, it would have quickly failed. The problem, according to Vogel, is the direction of the grain, which in a salami‑style slice of wood cannot support weight on its edge. Under strain, it would quickly deform. Kay’s solution—as is evident from early wheel design—was to build a composite wheel out of multiple vertically cut planks. Kay would have had to carefully dowel these cuts together, and then shape them into a perfectly round wheel.

The size of Kay’s wheels would also have been critical. Too small and the wagon cannot surmount any potholes, too large and the already heavy vehicle becomes immobile.

The genius of Kay’s craftsmanship lies not in any single one of these realizations; it’s in all of them. The wagon, as Anthony notes, could not have been put together in stages. It’s all‑or‑nothing. Either it works, or it doesn’t. But even with Kay’s crafting genius, his wheel would have been uselessly massive were it not for oxen.

Cattle began as wild aurochs before the late Natufians of Turkey domesticated them some 10,000 years ago. At first the Natufians used them exclusively for their meat and milk, but by the early fourth millennium BCE, the Maykop culture living in what is now Ukraine began to castrate the males and use them as work animals. The process of turning cattle into oxen and breaking them to the yoke would not have been pleasant. “It represented an entirely new level of domestication,” writes the archaeologist Sabine Reinhold, “far beyond earlier intrusions into animal lifestyles.” It involved castration, violence, and the infliction of pain. The animals “become lethargic,” Reinhold writes. “Their spirits are broken.”

It wasn’t just the oxen who suffered. Tellingly, the early Yamnayan wagon driver who was uncovered by archaeologists suffered 26 separate bone fractures throughout his life, in addition to arthrosis in his spine, left ribs, and feet. His life was a brutal one, but perhaps not unusual. Many of the earliest Yamnayans buried with wagons show numerous broken bones, particularly on their hands and feet, probably because submitting oxen to the yoke was a violent struggle between man and animal. The Maykop buried their people with nose‑ringed cattle, and some archaeologists speculate it was as a celebration of them having mastered the beast.

When Kay first yoked his oxen to his several‑hundred‑pound, 3‑ by 6‑foot wagon, complete with screeching wooden components and a team of oxen straining to haul it at a walking pace, he changed farming forever. Where it once took a village to haul a farm’s heavy loads, with a wagon and a team of oxen it took only a family.

As a result, Yamnayan families, using their wagons as mobile homes, spread away from their clustered villages into the vast, unexploited Eurasian steppes—and then beyond.

Their cultural imprint is evidenced even today.

The Yamnayan rolled down from the high steppe into Europe and East Asia, bringing their wagons, culture, and language. Today, 45 percent of the world’s population speaks a tongue descended from Kay’s PIE. Languages as disparate as English, Greek, Latin, Sanskrit, Portuguese, Spanish, Swedish, Slovak, Pashto, Bulgarian, German, and Albanian, to name a few, can all trace their roots back to PIE.

Recent DNA evidence supports a similar conclusion: the Yamnaya culture moved from the steppes and swamped the cultures to its south and west. Their massive wagons played a large role in their cultural domination, but their smallest stowaway may have played an even larger one. Geneticists have located the bacterium Yersinia pestis, an ancient version of the germ responsible for the Black Death, in 5,000‑year‑old teeth found in Central Russia and believe the Yamnaya may have unwittingly wielded a biological weapon as they rolled into Europe.

Perhaps the plague made Kay one of its early victims. Or he may have died from an accident. Whichever it was, the early popularity of his invention is an indication Kay may have been one of the few ancient inventors to have been recognized within his lifetime. And because it became the funeral custom of the Yamnaya to bury drivers on their wagons, perhaps Kay was the first.

From Who Ate the First Oyster?: The Extraordinary People Behind the Greatest Firsts in History by Cody Cassidy, published by Penguin Books, an imprint of Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2020 by Cody Cassidy.

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