Old Native Americans were among the first coppers | Science

A group led by archaeologist Michelle Bebber of Kent State University, Kent, made these replicas of copper arrowheads and knives made by people from the Old Copper Culture of North America.

Michelle Bebber / Kent State University Experimental Archeology Lab

By David Malakoff

About 8500 years ago, hunter-gatherers living on Eagle Lake in Wisconsin discovered a conical, 10-centimeter-long, pristine point made of real copper. The neat point, which is used to shoot a big game, illuminates the technological impact of the New World – and a puzzle. A new study of that artifact and other traces of prehistoric mining concludes that the so-called Old Copper Culture, then mysteriously gone, appeared much earlier than previously thought.

The dates show that early Native Americans were among the first people in the world to mine metal and invent it mechanically. They also suggest that regional climate change may help explain why, after thousands of years, the intelligent metallurgists abruptly stopped making most copper and copper tools. they largely returned to stone and bone tools.

The largest and most real copper deposits are found in the Earth around the Great Lakes of North America. At some point, Native Americans learned to cut the ore and heat, hammer, and grind it into tools. They left behind thousands of countless copper mines and tools, including projectile lethal points, large knives and axes, and fish hooks and awls. Today, it is not uncommon to meet local residents “who have a bucket of copper products [that they’ve found] away in their cellars, ”says David Pompeani, a geologist at Kansas State University, Manhattan, who studies ancient mining.

When researchers began to date the artifacts and mines, they saw an alarming pattern: The dates suggested that the people of Ancient Culture began to make about 6000 metal tools. years ago and then, for reasons that were not clear, copper tools that were largely abandoned about 3000 years ago. After that, early Native Americans used copper mainly for smaller, less useful, decorative materials, such as beads and bracelets. “History is just as special,” partly because many ancient cultures did not abandon metal tools once they learned how to make them, Pompeani says.

About 10 years ago, Pompeani began a medical investigation that cast doubt on the Old Copper timeline. He extracted sedimentary corals from lakes adjacent to prehistoric mines on the Keweenaw peninsula of Michigan and Royale Island and measured concentrated metals in the corrugations, including lead and titanium, which were released by the processing the mine. Studies have shown that copper mining began about 9500 years ago in some areas – some 3500 years earlier than once thought. It also ended earlier, about 5400 years ago, Pompeani reported The Holocene in 2015.

In laboratory experiments, replica Old Copper Culture arrowheads performed about the same as stone arrowheads. Perhaps that is why the people of Old Copper Culture abandoned copper points after using them for thousands of years.

Michelle Bebber / Kent State University Experimental Archeology Lab

Now, a team led by Pompeani is providing new evidence for the revised timeline. The researchers used innovative methods to reconstruct 53 radiocarbon dates – including eight newly collected dates – associated with the Ancient Copper Culture. Some came from wood or cord still attached to splinters; others came from charcoal, wood or bone found at mines and human burials. The oldest artifact with a reliable date appears to be the 8500-year-old projectile point found in Wisconsin.

This month in Radiocarbon, the team reports that the most reliable dates, along with the sediment data, show that the Ancient Copper Culture appeared at least 9500 years ago and reached between 7000 and 5000 years ago. back. That makes it at least as old, and perhaps older, as the copper-working cultures recorded in the Middle East, where archaeologists have unearthed a copper column believed to be 8700 years old. age.

The oldest window for the Old Copper peak did not surprise archaeologist Michelle Bebber of Kent State University, Kent, who studied the culture. The dates confirm “those hunter-gatherers [were] very ingenious, ”she said, and willing to“ constantly experiment with novel materials. ”

But why did the copper test suddenly end? Bebber’s work in replicating Copper-style arrowheads, knives and awls shows that they were not necessarily superior to the other options, especially after being sensitive in time and effort. required to make metal tools. In controlled laboratory experiments, such as firing arrows into flesh-like blocks of clay, she found that stone and bone tools were mostly just as effective as copper. That could be because Great Lakes copper is surprisingly real, which makes it soft, unlike harder natural copper alloys found elsewhere in the world, she says. say. Only copper awls were better than bone hole punchers.

Pompeani has identified another partner that may have become extinct Old Copper about 5000 years ago. Sediment cores, tree ring data, and other evidence show that a stable dry spell hit the area around that time, he says. This could have eliminated social and ecological impacts which made it difficult to spend time and resources making copper tools. Over time, copper may have become a luxury item, used to signify social status.

But copper awls followed this trend: They required very little ore to make, Bebber notes, and the people of the Great Lakes continued to use them for thousands of years.