This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In 1967, a Malawian farmer stumbled upon a hidden hoard of eight copper ingots buried beneath a tree. Now, more than half a century later, scientists have traced the metal to its source: a copper mine nearly 800 km (500 miles) away.
The discovery, published in the Journal of Archaeological Science: Reports, reveals how Iron Age traders moved copper across vast stretches of southern Africa, with locals making business decisions much like we do today, choosing the longer but safer route by canoe and paddling down major rivers rather than opting for the more troublesome direct overland trek. "It's a proud moment for Malawian archaeology and a great reminder that our ancestors were far more connected to the wider world than is often appreciated," said Smeda Matundu, chief curator of the Chichiri Museum. Of the eight ingots found in the late 1960s, only five remain, with the other three having gone missing.
These ingots are similar in style to other X-shaped ingots found across Zambia and Zimbabwe, dated between the 14th and 18th centuries, but they are also somewhat of an oddity, being far lighter and rougher than any other ingots, the study reported. The team quickly got to work, discovering that these ingots were not made by trained metalworkers. Instead, they were the result of someone pressing normal ingots into moist sand, leaving behind a rough mold that was unable to capture the finer details of a normal ingot but could recast them into thinner copies.
It was a quick and easy method. They then buried them, though to what end remains unknown. "It's a complete mystery," Jay Stephens of New York University said.
"The fact that someone decided to hide these ingots under a large tree is quite curious. Perhaps they intended to come back for them, but never did." Their find spot at Chombe in Malawi is notable, too: Malawi has no copper ore deposits, so the ingots had to have traveled from somewhere else. According to the study, small deposits in neighboring Mozambique are an unlikely source because their use was limited, leaving few alternatives.
They include the world's largest copper ore deposits, located in the Copperbelt on the Zambia–Democratic Republic of the Congo border, and Kipushi, an old copper mine near Lubumbashi, DRC. To figure this out, the team turned to lead isotopes. "Think of an automobile—both a bus and a sports car perform the same base function, despite their obvious size and weight differences," Stephens said.
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