Thirteen thousand years ago, human existence depended on clever ways to survive life among snow and ice. Now, scientists think these solutions were even more ingenious – and brutal – than we thought, as Ice Age hunters probably crafted a weapon to make animal prey like mammoths and sabre-tooth cats impale themselves.

The discovery could finally solve a decades-long debate about how these ancient tools, sharp rocks known as Clovis points, were used. Thousands of Clovis points have been found all over the US, ranging from the size of a human thumb to a smartphone, and made from rocks like chert or flint.

Previously, researchers thought the razor-sharp rocks topped spears that talented hunters would throw at their giant prey. These included mammoths, mastodons (similar to mammoths but more closely resembling modern-day elephants) and bison. That, or the sharpened rocks helped humans butcher wounded animals they had scavenged.

But the new study, published in the journal PLoS ONE, suggests we may have got it all wrong. The authors, archaeologists from UC Berkeley in the US, think the weapons were used to ingeniously trap and maim charging animals – including, they think, as a defensive move against sabre-tooth cats.

So how does this work? They think the hunters used them by planting the base of Clovis point-topped spears into the ground, with the spike facing upwards at an angle. Then, when a charging animal met them, its own force would drive the spear deep into its body. Given a mammoth could weigh as much as nine tonnes, this is likely to have been more damaging than even the strongest of ancient hunters thrusting a spear into the animal.

"This ancient Native American design was an amazing innovation in hunting strategies," said Scott Byram, first author of the paper. "This distinctive Indigenous technology is providing a window into hunting and survival techniques used for millennia throughout much of the world."

Finding this out required some bizarre methodologies. While analysing artworks and sources of writing from around the world may be normal, the researchers also ran an experimental simulation of this hunting technique.

Three sharpened rocks, black, grey and pink, in a row. These are replicas of Clovis points, the Ice Age weapons used to hunt mammoths. — These replicas of ancient Clovis points show their distinctive flute near the base. These are the weapons that may have brought down the mammoths. - Photo credit: Scott Byram

Essentially, they built a test platform to see how much force a replica spear system could withstand before breaking. But next, Byram and his team plan to build a fake mammoth to further test their theory, using a slide or pendulum to thrust it down onto a Clovis point replica.

This impaling technique, known as pike hunting, has been used elsewhere in human history. For example, similar planted pikes have been used to injure horses during warfare.

But in the Ice Age, this technique would have been crucial for survival as the hunters could re-use their weapons – rather than risk losing or destroying them by throwing them at an animal. Back then, finding suitable rocks and the right kind of straight wooden poles for the spears would not have been easy in such a snowy environment.

"Sometimes in archaeology, the pieces just start fitting together like they seem to now with Clovis technology, and this puts pike hunting front and centre with extinct megafauna," Byram said.

"It opens up a whole new way of looking at how people lived among these incredible animals during much of human history."

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