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From Esoteric to Everpresent

By Kevin Foley Article published September 4, 2002

Jim Petersen, professor of archaeology, spends his career immersed in the distant past. So he was surprised this summer to find some of his "esoteric" interests near the center of a media boomlet. When Petersen arrived in Brazil for a conference, he was greeted by a writer from Science and a documentary crew from the BBC.

"It was unbelievable," he says. "Suddenly here's this guy from Science who wants to talk with us, and these documentary guys who wanted to film us everywhere."

The conference, the first devoted to a peculiar type of fertile human-made soil in the Amazon, attracted researchers from a variety of disciplines as well as the reporters. Petersen, who works in the region annually, has excavated sites rich in the soil. He also contributed a chapter about the soil, which is the mysterious product of long habitation by ancient people, to a book accompanying "The Unknown Amazon," a 2001 exhibition at the British Museum.

Petersen thinks the rich earth, called terra preta, is "a gift from the past" in a largely arid region. It's intriguing to Petersen and his colleagues for a variety of reasons, not least that it is the product of long and intense human habitation. Human hands, of course, are usually thought to degrade soil rather than improve it.

Growing interest in the soil has thrust Petersen and his archaeological colleagues from antiquity into hot current debates about sustainable agriculture and soil science. The Aug. 9 Science article puts the findings into context, and describes the diverse group of inter-disciplinary researchers working in the field.

"It's exciting, it's a rare opportunity for archaeology to directly engage a current problem," Petersen says of the terra preta work. "We are increasing our knowledge of fertility in tropical soils, which may offer clues in how to positively manage soils that are increasingly difficult to cope with. If we better understand these fertile soils in the first place, we might understand more about how to recreate them today."

The BBC crew's documentary, the first ever filmed on Amazonian archaeology, drew much of its narrative from Petersen's book chapter and will include footage from his group's fieldwork sites. It airs in Britain on October 27, and may subsequently be picked up by an American network.

In classic Murphy's Law form, the team Petersen collaborates with made a major discovery shortly after the film crew and reporters had left the region. They found an early Paleo-Indian site in Iranduba, Brazil. The site is about 11,000 years old and is the first professionally recovered location in the area from that particular time period. The group found a spear point there, one of only four or five like it ever discovered in the Amazon. Even more evocative, they found dark, terra preta-like earth, expanding the puzzle of the strange soil. According to the current thinking on the material, it shouldn't have been there.

"Terra preta is taken to be a product of large social groups over long period of time," he says. "But now we have dark soil in a far older site. The mystery is, how did the earliest occupants of the Amazon create it? Were they not small social groups as we had thought? Did they stay in place longer than we expected? It's another dimension to a fascinating set of questions."

For more background, see Lynda Majarian's article, "Rainforest Research Hits Pay Dirt."