The term American Web, which the text introduces in Part 4 and figures heavily in parts 5 and 6 as well, refers to the communications, trade, and political network that emerged in present-day North, Central, and South America before the arrival of Europeans. Part 6 discusses the contact between the American Web and the Old World Web. Throughout the text, the authors highlight how the American Web had fewer domesticable animals and weaker communications and trade links than the Old World Web to explain why the American Web lagged behind the Old World Web in transformative expansion and tightening.

The Anthropocene refers to an age of history in which the scale of human activity has substantially altered Earth’s surface, atmosphere, oceans, and nutrient cycling. Some scholars place its origins in the period when human agriculture began, while a growing group of scholars agree that it began in the 1950s. This text uses the term in the Introduction, identifying the Anthropocene as a “new era of earth history [...] in which our actions are the most important factor in biological evolution, and in several of the planet’s biogeochemical flows and geological processes” (7-8). Though the phrase most important suggests that the authors fall within the latter group of scholars, they discuss human impact on the environment beginning in the Paleolithic Era.