To prime the men for going out to slash and burn the forest to clear a new cassava patch for Ana María’s brother, they were drinking chicha—gallons of it. Even the children slurped ceramic bowls full of the milky, sour beer brewed from cassava pulp, fermented with the saliva of Zápara women who chew wads of it all day. Two girls with grass braided in their hair passed among the throng, refilling chicha bowls and serving dishes of catfish gruel. To the elders and guests, they offered hunks of boiled meat, dark as chocolate. But Ana María Santi, the oldest person present, wasn’t having any.

Although the rest of the human race was already hurtling into a new millennium, the Zápara had barely entered the Stone Age. Like the spider monkeys from whom they believe themselves descended, the Zápara essentially still inhabit trees, lashing palm trunks together with bejuco vines to support roofs woven of palm fronds. Until cassava arrived, palm hearts were their main vegetable. For protein they netted fish and hunted tapirs, peccaries, wood-quail, and curassows with bamboo darts and blowguns.

They still do, but there is little game left. When Ana María’s grandparents were young, she says, the forest easily fed them, even though the Zápara were then one of the largest tribes of the Amazon, with some 200,000 members living in villages along all the neighboring rivers. Then something happened far away, and nothing in their world—or anybody’s— was ever the same.

What happened was that Henry Ford figured out how to mass-produce automobiles. The demand for inflatable tubes and tires soon found ambitious Europeans heading up every navigable Amazonian stream, claiming land with rubber trees and seizing laborers to tap them. In Ecuador, they were aided by highland Quichua Indians evangelized earlier by Spanish missionaries and happy to help chain the heathen, lowland Zápara men to trees and work them until they fell. Zápara women and girls, taken as breeders or sex slaves, were raped to death.