Weisman describes a “barn raising” event among the Zápara, an Indigenous people of the Ecuadoran Amazon, at which everyone is drunk on cassava beer. After their 200,000-member society was nearly wiped out by the early 20th-century rubber-tapping industry, early 2000s government funding supported a cultural revival on a small portion of their ancestral land. Because the Zápara had abandoned their traditional hunting-and-gathering practices in favor of slash-and-burn farming of cassava, however, the denuded rain forest now supported much less wildlife, leading the Zápara to start hunting the spider monkeys from whom they believed themselves to be descended. “When we’re down to eating our ancestors,” a Zápara elder reflects, “what is left?” (3).

Weisman lays out the thought experiment that constitutes the premise of the book, questioning how the Earth would respond if the entire human species were instantaneously wiped out in a manner that left the rest of the natural world intact:

How soon would, or could, the climate return to where it was before we fired up all our engines? […] Could nature ever obliterate all our traces? How would it undo our monumental cities and public works, and reduce our myriad plastics and toxic synthetics back to benign, basic elements? Or are some so unnatural that they’re indestructible? (4).