This volume presents a new model of borderlands interaction and several applications of it, pushing frontier studies in interesting directions. The editors have created a graphical representation of interaction, which they call the Cross-Cultural Interaction Model (CCIM), which attempts to account for levels of intensity of exchange between two or more groups. This circular representation allows researchers to display multiple groups, their range of interaction (limited, selective, or intense), and degrees of interaction between groups (i.e., one- or two-sided). One strength of the model is its flexibility, as evidenced by the inclusion of case studies from several world areas. The theoretical underpinnings of the model are published elsewhere, which is a drawback for the book itself, because while the model has great potential for studies of interaction, the varied uses of the model without explicit grounding in theory can at times result in a lack of clarity.

As stated, the flexibility of the model is one of its strengths, and contributors to this volume were given free range to adapt the model to address various research questions. Some, like Wells's study of Roman Europe after AD 100, Feur's study of Late Bronze Age Thessaly, and Costion and Green's focus on the prehistory of interactions in the Moquegua Valley of Peru, apply the model at large scales. Wells models four zones of far-reaching interaction and shows that as distance from Rome increased, frontier areas were more likely to exhibit agency and autonomy. Feur draws upon acculturation theory but shows that the CCIM accounts for ethnicity, class, and terrain to illuminate “patterns of intercultural interaction” (p. 56). Costion and Green apply the CCIM to demonstrate that access to drainages was key to the evolution of exchange networks in the Moquegua Valley from 11,000 BP to AD 1450. On the one hand, these studies usefully demonstrate how interactions shifted, and they allow the authors to ask why those shifts occurred. However, the broad scale prevents the authors from delving into much detail to ask questions such as why certain items were adopted when others were not and how those items were used in different ways by borderland groups.

Other chapters take more fine-grained scalar approaches, which allow them to ask and sometimes to answer these questions. Toft's chapter focuses on specific items that Inuit groups in Greenland acquired from Dutch, Danish, German, and British whaling ships and Danish missionaries and colonists during the late 1600s and early 1700s, items such as barrel hoops, glass beads, and especially steel saw blades for ulo knives. He shows how and why trade changed by focusing on how the uses of those items by different native groups changed over time. Palumbo rightly critiques our understanding of gold as a symbol of chiefly power in Costa Rica and Panama between AD 750 and 950. Using archaeology and documentary sources such as nineteenth-century written accounts of looted burials, he identifies inflationary and what he terms deflationary (i.e., devaluation) trends that altered how gold was used and by whom; that is, it was not access to gold but access to a lot of gold and other items that demonstrated “such lavishness as evidence of instability” (p. 161), rather than access to gold symbolizing elite power. Buchanan's chapter on the Mississippian Southeast takes a unique and thoughtful approach by literally turning the model on its head to show that religion affected interaction between Cahokia and neighboring Mississippian groups during the early second millennium AD. Her consideration of several archaeological sites near Cahokia demonstrates that there were power realms and sacred spaces that impacted who exchanged with whom and when; this angle is often ignored in interaction studies. Smith and Buzon's chapter on the Nubian frontier of Egypt between 1680 and 656 BC takes a diachronic view on its development. Although the details they discuss can be overwhelming at times, they use linear and circular variations of the CCIM to demonstrate variation over time and space.

The concluding chapter by the editors evaluates the uses of the model within the book. Although this synopsis allows readers to consider the chapters as a group, an outsider's perspective comparing CCIM with other models of borderlands interaction as well as its relevance to archaeological study of exchange would have been beneficial. Overall, this volume outlines models for viewing interactions differently than archaeologists typically have—and in many cases, to better understand those interactions. I commend Green and Costion for pushing boundary studies in important new directions, and I look forward to seeing applications of their approach in future archaeological research on borderlands.