Human Origins / Archaeology

On August 13, 2005, American archaeologist James Petersen, Brazilian archaeologist Eduardo Neves, and two colleagues pulled up to a restaurant on a jungle road near Iranduba in the Brazilian Amazon to have a beer. At about 6:45 p.m., two young men, one brandishing a .38 revolver, entered the restaurant and demanded the patrons’ money. The archaeologists turned over their money and the bandits started to leave. Then, almost as an afterthought, one of them shot Petersen in the stomach. Neves and the others raced Petersen to the hospital, but their friend bled to death before they could reach help.

State and municipal police reacted quickly to the news, cordoned off roads, and brought suspects to the restaurant for identification. Within 24 hours the police had arrested the two armed bandits and their driver and learned there were two others involved. The crime was front-page news in Manaus, the capital of the state, a city of more than a million about an hour north of the study site, across the Rio Negro. After a 21-day manhunt through the jungle, the remaining two fugitives were captured, and when the state police brought the criminals back, the Iranduba chief of police, Normando Barbosa, says, “there were hundreds of people lined up on the road that wanted to lynch the killers.”

This outrage reflected a response not only to the crime but also to the victim. Over the past decade, Petersen, Neves, and their band of archaeologists had become local heroes, earning the appreciation of the surrounding community during seasonal digs conducted on the peninsula that separates the Rio Negro and Amazon rivers. At more than 100 sites across the peninsula, Petersen and his colleagues had unearthed evidence of early civilizations that were far more advanced, far more broadly connected, and far more densely occupied than that of the small bands of nomadic hunter-gatherers previously hypothesized for the region. Before the Europeans arrived, this peninsula in the heart of the Amazon was home to communities with roads, irrigation, agriculture, soil management, ceramics, and extended trade. These civilizations, Neves says, were as complex as the southwestern Native American cultures that inhabited Chaco Canyon and Mesa Verde. But due to the scarcity of stone in the Amazon, the people built with wood, and over time the structures disintegrated, leaving little evidence of the culture.

One legacy remains, however: their soil. Terra preta de Indio—Portuguese for “Indian black earth”—is prized among local farmers, and it is a direct contribution of the vanished Amazonian cultures. While most Amazonian earth is notoriously nutrient poor, yellowish, sterile, and unscented, there are extensive patches of soil that are mysteriously dark, moist, fragrant, and filled with insects, microbial life, and organic matter. Scholars have come to realize that by devising a way to enrich the soil, the early inhabitants of the Amazon managed to create a foundation for agriculture-based settlements much more populous than scholars had thought possible.

Petersen had called the soil a gift from the past; he believed that studying it would reveal the region’s past cultures in a new, much more complex light. At the time of his death, he and his colleagues had been developing a workshop for teachers in the region on the science and archaeology surrounding terra preta. The discovery held meaning for more than archaeologists, however. Figuring out the composition of dark earth and how it was formed offers a way to improve soil fertility for today’s small farmers and also curb carbon emissions from the fires that these farmers set to clear the forest. Yet after Petersen’s murder the project was shut down, and those who had gathered for both the workshop and the August field season were sent home. Had the Amazon turned too dangerous for its inhabitants to learn their own ancestors’ secrets?