Ancient Americans show metallic flair

Science News, Nov 7, 1998 by Bruce Bower

Scientists working at an ancient ceremonial center in Peru can be forgiven if they break into a chant of "Hallelujah, foiled again." Copper and gold foil unearthed there dates to about 3,000 years ago, offering the oldest known evidence of metalworking in the New World.

Metallurgy in this region arose in what is believed to have been a relatively small society without strict social classes, assert archaeologist Richard L. Burger and geologist Robert B. Gordon, both of Yale University. Traditional theories hold that large states characterized by stark social divisions held a monopoly on technological innovations such as metallurgy.

Burger and Gordon present their findings in the Nov. 6 Science.

"This is an extremely important paper," comments archaeologist Daniel Sandweiss of the University of Maine in Orono. "It finally gives us a clear indication that metallurgy was invented independently [in the New World] and developed in ways that were similar to its beginnings elsewhere."

The Yale researchers directed excavations at Mina Perdida, located on a large, natural terrace above a coastal valley. A flat-topped, terraced pyramid dominates the site. Digging focused on two long, raised mounds arranged in a U shape and framing a ceremonial plaza.

Mina Perdida and nearby sites have already yielded remains of religious rituals and other community activities, and of households situated on their fringes. These locations were abandoned before the rise of Peruvian cultures that produced smelted copper objects by around 2,000 years ago.

Radiocarbon dating of artifacts found in the same sediment as the copper and gold-foil fragments yields an age of between approximately 3,120 and 3,020 years, Burger and Gordon report.

Metalworkers at Mina Perdida understood copper's natural properties and how to manipulate the metal in sophisticated ways, Burger holds. Microscopic analysis of foil specimens indicates that they were expertly hammered into thin foils. In some cases, a heating process was used as part of foil production. Three copper foils have folded corners and edges. Fragments of gold attached to two copper foils indicate that Mina Perdida artisans made gilded objects.

Foils may have been attached to ceremonial attire or objects in order to reflect light during ritual performances, Burger suggests. Ancient onlookers probably marveled at the capture and redirection of a natural force as significant as the sun, he says.