Muddy timeline.
Sediments from Laguna Pirhuacocha reveal the rise of large scale metal work 400 years prior to the rise of the Inca.

Incas Lose a First

The Incas fashioned gorgeous gold, silver, and copper statuettes and ornaments, but they shouldn't get credit for introducing "industrial scale" metallurgy in South America, as researchers long thought. Fresh evidence from ancient lake sediments in Peru reveals that extensive smelting of copper and silver began around 1000 C.E. some 450 years before the rise of the Inca civilization. The findings suggest that the Inca, and later the Spanish, likely looted the artifacts, leaving behind little evidence of the earlier craftsmanship.

Reconstructing the history of metalsmithing in the Andes has been challenging because so few early artifacts remain. But several years ago Alexander Wolfe, a paleolimnologist at the University of Alberta in Canada, and colleagues realized that the Bolivian lake sediments they had been studying to discern ancient climate patterns likely also preserved a detailed timeline of the history of local metal smelting. Metals in the smoke from a smelter rain down and get trapped in successive layers of lake sediment. In 2003, Wolfe and a colleague reported in Science that they had found evidence of extensive silver smelting in a pre-Incan culture in Bolivia. But the timing of around 1000 C.E. was curious, as it coincided with the fall of the Tiwanaku empire that dominated the region at the time.

In hopes of finding further clues, Wolfe and colleagues expanded their search to lake core sediments from Laguna Pirhuacocha, a small lake in the mining region of Morococha in Peru. The area was home to the Wari empire, the largest in the Andes before the Inca. As in their earlier study, the researchers tracked sediment levels of lead, titanium, zinc, bismuth, antimony, copper, and silver. They also used radiocarbon dating and other techniques to determine the ages of different strata within the sediment core. The results were clear, Wolfe says.

In the 15 May Environmental Science & Technology, the researchers report that again around 1000 C.E. they found a spike in several metals, this time those associated with copper smelting. And again the date was curious, since it occurs after the fall of the Wari. Wolfe says the timing of the spike is consistent with previous suggestions that Wari and Tiwanaku empires fell because of a drought or some other environmental collapse. The rarity of artifacts from this metal-working hints that the Incas and Spanish made off with the objects. But the timing wasn't the only thing that stood out. Around the rise of the Inca, the researchers found that the metalsmiths shifted their smelting from copper to silver. That, they suggest may have been to pay a heavy tax imposed by Incan rulers, who favored the metal.

"I think it's pretty exciting stuff," says Mark Brenner, a paleolimnologist at the University of Florida, Gainesville. Brenner notes that the levels of lead and other potentially dangerous metals appear to be high enough that they may have caused widespread health effects, such as muscle and joint pain and memory troubles, among the locals. Next up, he says, it may be worth examining the bones of skeletons from the time to see whether they show effects from the rise of the Andes' original large scale metalworks.

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