Uncannily preserved in the sands of New Mexico, archaeologists have discovered the oldest evidence yet of a vehicle used by humans: drag marks, along with footprints, left in the ground that have been dated to 22,000 years ago.

As detailed in a study published in the journal Quaternary Science Advances, these marks were left behind by a type of sledge known as a travois. Think of it as a wheelbarrow without the wheels.

Typically comprising two wooden poles held in each hand at the front, and intersecting at the back in a V or X-shape, a travois would have been pulled across the ground, carrying meat, game or other supplies. Their usage is well-known to scientists — but this is by far the oldest example, predating the invention of the wheeled vehicle in Mesopotamia by some 17,000 years, according to researchers.

"There's nothing this old," study author Matthew Bennett at the University of Bournemouth told New Scientist.

The ancient runnels, as the authors describe them, were discovered in the dried mud of a bygone lake in White Sands National Park in New Mexico, hidden by sediment for untold ages, and finally exhumed by a chance mix of natural erosion and careful excavation by researchers.

"The drag-marks extend for dozens of meters before disappearing beneath overlying sediment," explained Bennet in a writeup for The Conversation. "They clip barefoot human tracks along their length, suggesting the user dragged the travois over their own footprints as they went along."

Rarely were they found in isolation, with the researchers discovering other tracks of footprints nearby all heading in the same direction. In many cases, based on their size, the prints were left behind by children.

"We believe the footprints and drag-marks tell a story of the movement of resources at the edge of this former wetland," Bennett wrote in The Conversation. "Adults pulled the simple, probably improvised travois, while a group of children tagged along to the side and behind."

To New Scientist, Bennet added that while travois were often pulled by animals like horses in other cultures, the White Sands discovery only indicated human usage. It's possible some of the marks were left by dragging firewood, "but this does not fit all the cases we found," Bennett wrote in his Conversation essay.

But perhaps the discovery's most staggering implication is that humans may have crossed into the Americas much earlier than commonly believed, with dominant theories — which are being increasingly challenged — holding that nobody made the trek until around 15,000 years ago.

"The peopling of the Americas debate is a very controversial one, but we're fairly confident about the dates," Bennett told New Scientist. "The traditional story is that the ice sheets parted and they came, but you can come through before the door closes, too."

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