The papaya orchard was so robust and healthy that it looked like an advertisement—the background image behind a celebrity endorser of a new papaya drink. Sweating in the equatorial sun, some of the researchers admiringly fingered the plump, pendulous green fruit, each the size of a baby’s head, wrapped in clusters around the trees’ sturdy trunks. Other scientists bent down and with equal approbation scooped up handfuls of dirt. The road to the plantation had been cut into the Amazon’s famously poor soil—it was the blaring orangered of cheap makeup, almost surreally bright against the great dark green leaves of the forest. But in the shade of the papaya trees the soil was dark brown, with the moist, friable feel that gardeners seek.

At first glance, the soil seemed similar to what one would find in, say, the grain belts of North America or Europe. After a more careful inspection, though, it looked entirely different, because it was full of broken ceramics. The combination of good soil, successful agriculture, and evidence of past Indian inhabitation was what had brought the scientists to the farm. I had been invited to tag along.

The orchard was about a thousand miles up the Amazon, two hours by ferry and bus from Manaus. Manaus, the biggest city on the river, is situated on the north bank of the Amazon, hard by its junction with the Negro River, a major tributary. *24 Between the two rivers is a tongue of land that, depending on your point of view, is either almost destroyed by development or quite lightly inhabited considering its proximity to a city of a million people. Near the tip of the tongue is the small village of Iranduba: a bush-pilot airport, a half-dozen lackadaisical stores, some bars with jukeboxes loud enough to knock birds from the trees, and docks for loading local farmers’ produce. A few miles outside Iranduba, on a bluff above the Amazon, stood the papaya orchard. It was one of the many small riverside farms operated by the descendants of Japanese immigrants.

In 1994 Michael Heckenberger, now at the University of Florida in Gainesville, and James B. Petersen, now at the University of Vermont in Burlington, decided to look for potential archaeological sites in the central Amazon. With a team of Brazilian scientists, Meggers had surveyed much of the river and its tributaries in the 1970s and 1980s and concluded there was little of archaeological relevance—further proof of the inescapability of ecological constraints. Believing that Meggers’s survey had been too coarse-grained, Heckenberger and Petersen decided to search a single area intensively. Joined by Eduardo Goés Neves of the University of São Paulo, several dozen of Neves’s students, and, later, Robert N. Bartone, of the University of Maine at Farmington, they found more than thirty sites at the Amazon-Negro junction, four of which they excavated fully. The papaya farm was one of the four. Now Neves, Petersen, and Bartone were leading a score of visiting researchers and a journalist on a tour of the site.

From the shade of a doorway, the father of the family watched us mill around with a tolerant smile. A teenage girl stood outside, listlessly sweeping at a cloud of yellow butterflies. Through the loosely placed boards in the wall floated the bark and jabber of a talk-radio show about the latest soccer perfidy from Argentina, Brazil’s hated rival. Although it was winter, the midday sun was hot enough to make sweat start out from the skin.

At the edge of the papaya grove were ten low earthen mounds that the team had identified as human-made. Carbon dating indicated that they were constructed in about 1000 A.D. The archaeologists had begun opening up the largest of the mounds. Already they had discovered nine burials, one body placed in a big funerary urn, all apparently interred at the same time. Because the scientists were unlikely to have uncovered the area’s only concentration of human remains in their first, exploratory test pit, they believed that the entire mound was likely to be full of burials—hundreds of them. “That suggests thousands of people lived here,” Neves said. “In 1000 A.D., that’s a big place.”

Shoving back his baseball cap, Neves levered himself into the excavation site, a six-foot, rectangular hole with the right-angled corners and precisely vertical walls that are a hallmark of archaeological investigation. One of the visiting researchers passed down a Munsell soil-color chart. Resembling strips of paint-color samples, these are used by pedologists (soil scientists) to classify soils. Neves scraped the wall lightly, exposing fresh earth, and pinned the chart to the wall with a big-headed nail. From the top of the dig he dangled a measuring tape—alternating ten-centimeter strips of red, white, and green—to indicate depth. Digital cameras ratcheted and whined. It was a vest-pocket version of the inspection of Folsom by the graybeards.

Neves had a little trouble hanging the tape because he couldn’t find a place where it wouldn’t get snagged on the broken ceramics protruding from the walls. They bristled from the side of the dig in a profusion that reminded me of the Beni mounds, hundreds of miles upstream. Some of the pieces seemed to form horizontal layers. As in the Beni, the ceramics had apparently been smashed deliberately, perhaps to build up the surface.

I asked Petersen, a ceramics specialist, how many plates and bowls and cups were in the mounds. He pulled out a scrap of paper and a pen and scribbled some numbers. In a minute or two he looked up. “This is a rough, back-of-the-envelope-type estimate,” he warned, showing me the result: the single mound we were standing on might contain more than forty million potsherds. “Think of the industry required to produce that much pottery,” Neves said. “Then they just smash it. Look at the way they piled up this good soil [to make the burial mound]—it’s all wasteful behavior. I don’t think scarcity was a problem here.”

The ecological constraints on tropical soils are in large part due to the gravitational energy of raindrops. Rainfall, drumming down day in and day out, pounds the top few inches of earth into slurry from which nutrients are easily leached and which itself easily washes away. In uncut forest, the canopy intercepts precipitation, absorbing the physical impact of its fall from the clouds. The water eventually spills from the leaves, but it hits the ground less violently. When farmers or loggers clear the tree cover, droplets shoot at the ground with more than twice as much force.

Slash-and-burn minimizes the time in which the ground is unprotected. Intensive agriculture is much more productive but maximizes the land’s exposure. This painful trade-off is why ecologists argue that any attempt by tropical forest societies to grow beyond small villages has always been doomed to fail.

According to Charles R. Clement, an anthropological botanist at the Brazilian National Institute for Amazon Research (INPA) in Manaus, though, the first Amazonians did avoid the Dilemma of Rainfall Physics. Speaking broadly, their solution was not to clear the forest but to replace it with one adapted to human use. They set up shop on the bluffs that mark the edge of high water—close enough to the river to fish, far enough to avoid the flood. And then, rather than centering their agriculture on annual crops, they focused on the Amazon’s wildly diverse assortment of trees.

In his view, the Amazon’s first inhabitants laboriously cleared small plots with their stone axes. But rather than simply planting manioc and other annual crops in their gardens until the forest took them over, they planted selected tree crops along with the manioc and managed the transition. Of the 138 known domesticated plant species in the Amazon, more than half are trees. (Depending on the definition of “domesticated,” the figure could be as high as 80 percent.) Sapodilla, calabash, and tucumá; babaçu, açai, and wild pineapple; coco-palm, American-oil palm, and Panama-hat palm—the Amazon’s wealth of fruits, nuts, and palms is justly celebrated. “Visitors are always amazed that you can walk in the forest here and constantly pick fruit from trees,” Clement said. “That’s because people planted them. They’re walking through old orchards.”

Peach palms—the trees through which I looked at the Amazon from Painted Rock Cave—are Clement’s favorite example. Giddily tall and straight, they have up to a dozen stalks, with a protective mat of spikes wrapped around the bottom of the tree. The protection is little needed; peach palm wood is hard enough that in the Beni it was used for saw blades. Bundles of orange or red fruit hang like clusters of bocce balls from the base of the fronds. The fruit is soaked with oil and rich in beta-carotene, vitamin C, and, surprisingly, protein. When dried, the white or pink pulp makes flour for thin, tortilla-like cakes; when boiled and smoked, it becomes hors d’oeuvres; when cooked and fermented, it makes beer. (The sap also makes a kind of wine.) Two crops a year are not uncommon; in terms of yield per acre, peach palms are typically much more productive than rice, beans, or maize. Trees begin producing fruit after three to five years and can continue for another seventy years. Like strawberries, peach palm throws out adventitious shoots. With a little care, these can be harvested for heart-of-palm—very tasty heart-of-palm, in my experience. Bactris gasipaes, as scientists call it, has more than two hundred common names: pupunha, cahipay, tembe, pejibaye, chontaduro, pijuayo. To Clement, the proliferation of names suggests the plant was used for many purposes by many cultures.

In the 1980s and early 1990s Clement measured peach palms throughout the Amazon basin. He learned that several physical characteristics, including fruit size, lay on a gradient with those apparently closest to the wild state in western Amazonia, near the Beni; the implication was that the tree might first have been cultivated there. Using a different method, Jorge Mora-Urpí, one of Clement’s collaborators, concluded that Indians might have bred the modern peach palm by hybridizing palms from several areas, including the Peruvian Amazon. Whatever the origin, people domesticated the species thousands of years ago and then spread it rapidly, first through Amazonia and then up into the Caribbean and Central America. Bactris gasipaes was in Costa Rica 1,700 to 2,300 years ago and probably earlier. By the time of Columbus, one seventeenth-century observer wrote, Native Americans valued it so highly “that only their wives and children were held in higher regard.”

Unlike maize or manioc, peach palm can thrive with no human attention. Tragically, this quality has proven to be enormously useful. In the seventeenth and eighteenth centuries many Amazonian Indians, the Yanomamo among them, abandoned their farm villages, which had made them sitting ducks for European diseases and slave trading. They hid out in the forest, preserving their freedom by moving from place to place; in what Balée calls “agricultural regression,” these hunted peoples necessarily gave up farming and kept body and soul together by foraging. The “Stone Age tribespeople in the Amazon wilderness” that captured so many European imaginations were in large part a European creation and a historical novelty; they survived because the “wilderness” was largely composed of their ancestors’ orchards. “These old forests, called fallows, have traditionally been classified as high forest (pristine forest on well-drained ground) by Western researchers,” Balée wrote in 2003. But they “would not exist” without “human agricultural activities.” Indeed, Amazonians typically do not make the distinction between “cultivated” and “wild” landscapes common in the West; instead they simply classify landscapes into scores of varieties, depending on the types of species in each.

After we had spoken for a while Clement took me out of his office and into INPA’s experimental forest. To my untrained eye, it looked much the same as the forests around the lodges outside Manaus that attract ecotourists, except that INPA staffers kept down the undergrowth. There was the same cool green light from the canopy, the same refulgent smell, the same awe-inspiring sense of variety. The air vibrated with the same inharmonic racket of squealing, burbling, croaking, and cheeping birds. Dribbling down some of the tree trunks were little runnels that looked like dried sap. On a previous visit to the Amazon I had seen runnels just like these on a rubber tree in an abandoned plantation. Thinking it was a drip of latex sap, I plucked at one. It was the cover for a termite superhighway. Termites boiled out of the little tunnel and all over my hand. Termites bite. Flapping my hand wildly, I leapt back from the tree. My sandaled foot landed on a ground-wasp nest. In this way I learned why some Amazonians have a jaundiced view of biodiversity. On Clement’s tour I kept my hands to myself.

It was July—winter in the Amazon, the worst time of the year for fruit. Nevertheless, Clement was able to find yellow bacuri and purple açai. He plucked what looked like a four-foot version of a string bean from a branch, split it lengthwise, and showed me flattened, shiny seeds arrayed along its length like teeth in a jaw. Each seed was the size of a thumb bone and nestled in a fluffy white coating. “Try this,” he said. “It’s the ice-cream bean.” I put a seed in my mouth and sucked on it. The coating did taste quite like vanilla ice cream, and was just as refreshing. Three or four more fruits followed, each equally strange to me. (This is what people like about biodiversity.) Peach palm was not in season, but he found another member of the same genus. The fruit, when peeled, was unappetizing—quite like soggy cardboard in color, texture, and flavor. Clement squeezed some pulp. Oil dribbled from his fingers to the ground. “This’ll put some calories into you,” he said.

Planting their orchards for millennia, the first Amazonians slowly transformed large swaths of the river basin into something more pleasing to human beings. In the country inhabited by the Ka’apor, on the mainland southeast of Marajó, centuries of tinkering have profoundly changed the forest community. In Ka’apor-managed forests, according to Balée’s plant inventories, almost half of the ecologically important species are those used by humans for food. In similar forests that have not recently been managed, the figure is only 20 percent. Balée cautiously estimated, in a widely cited article published in 1989, that at least 11.8 percent, about an eighth, of the nonflooded Amazon forest was “anthropogenic”—directly or indirectly created by humans.

Some researchers today regard this figure as conservative. “I basically think it’s all human created,” Clement told me. So does Erickson, the University of Pennsylvania archaeologist who told me in Bolivia that the lowland tropical forests of South America are among the finest works of art on the planet. “Some of my colleagues would say that’s pretty radical,” he said. According to Peter Stahl, an anthropologist at the State University of New York in Binghamton, “lots” of researchers believe that “what the eco-imagery would like to picture as a pristine, untouched Urwelt [primeval world] in fact has been managed by people for millennia.” The phrase “built environment,” Erickson argued, “applies to most, if not all, Neotropical landscapes.”

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