There are no other medieval European studies among the fifty-nine titles in the Yale Agrarian Studies Series, and precious few works focused on pre-industrial times. So the October 2020 publication of Jamie Kreiner's Legions of Pigs, amidst books about famine in Maoist China, the politics of environmental aid to Madagascar, and challenges to the Montreal Protocol, is a big accomplishment. It is also a step toward broadening the readership of both early medieval history and medieval environmental history, and toward reaching the "general readers who are interested in animals, agriculture, environmental history, religion, and the history of science" (x) who are Kreiner's other intended audience.

To address people unaware of who Justinian was (143), what geographical differences separate Continental from Mediterranean Europe (81-82), how the annona (86, 112-113) or transhumance (94) functioned, or what actually happened in the Dark Ages (4-5), Kreiner supplies thumbnail sketches, brief asides, and parenthetical definitions. Further, she writes in a folksy, colloquial register that is definitely accessible (more, perhaps, to North Americans), and is always pellucid. Neither the divagations into what specialists might consider basic information, nor the homespun rhetoric, deprive Legions of Pigs of impact. This is an eminently legible book.

Kreiner's study of pigs covers a lot of ground. It has a stupendous geographical range, discussing porcine affairs from Egypt to Greenland. It also ranges widely in chronology. The early Middle Ages are hard to define, but here they are "long." They encompass imperial Roman times and the twelfth century, when a Salernitan medical treatise called the Anatomia Porci was written (196) and when a fresco cycle went onto the walls of a church just north of Rome which, in a brilliant analysis, Kreiner connects to the belief that eating pork allowed people to be better Christians (200-202). Legions of Pigs is likewise ecumenical in its source base: alongside scientific treatises and paintings, to build her arguments Kreiner deploys laws, charters, biblical exegesis, hagiography, mosaics, ivory carvings, behavioral studies of several species of animal, settlement archaeology, palynology, and of course a lot of finely sifted osteoarchaeology. Though Kreiner thinks it "neither helpful nor interesting to generalize" (10) about early medieval environmental conditions, the synthesis (by nation) of zooarchaeological finds, hitherto fragmented and dispersed in local, specialist studies from all Europe and across the "long" early Middle Ages, is one of this book's major achievements.

Legions of Pigs advances two main arguments. First is the claim that the disparate evidence it assembles demonstrates that early medieval Europeans, from kings, to landowners, to peasants, thought ecologically about their circumstances thanks to their frequent encounters with pigs. In other terms, pigs were anything but passive commodities or "walking larders" (78). Enterprising and intelligent animals, they drove humans to adapt their husbandry, in an "ongoing process of co-domestication" (42). Pigs also induced people to confront the interconnectedness of even the tiniest components of an agroecosystem, and to see all the glory and wonder of God's creation in the apparently least significant aspects of nature.

A second argument Kreiner weaves through her book is about scale. She suggests that proper understanding of early medieval environments requires integrating the theological frameworks that contemporaries found most persuasive with minute knowledge of micro-ecological realities (local geology, vegetation, weather, etc., and the human strategies developed to cope with them, including the raising of pigs). The micro-ecological and the macro-cosmological were intimately connected by a (in these pages, too little explored) constant exchange between the learned and popular cultures of the early medieval period, both invested in the close observation and comprehension of nature in all its infinite variations.

These arguments invite a re-evaluation of the venerable notion that Christianization turned Europeans into environmental wrecking balls, persuaded that the natural world was at their disposal because its creator had stipulated as much in the beginning. Lynn White Jr.'s famous 1967 article inScience about Christianity's deleterious effects on medieval ecological relations persuaded many later environmental historians. They maintained that the impermanent natural world seemed inferior and subordinate to the supernatural one, thereby leaving medieval people, particularly scholars, unwilling and unable to examine natural phenomena attentively. An anthropocentric culture also licensed exploiting nature to the hilt. Kreiner offers good reasons to reject such positions (76-77).

Legions of Pigs is divided into five chapters, plus a shorter introduction and epilogue. Kreiner opens by laying out the case for seeing all early medieval nature as "part of a divine jigsaw" puzzle God wanted people to "piece together" in order to improve their souls (3), and for considering the exercise an "ecological ethic," albeit one different from modern environmentalism. The first chapter is on early medieval accounts of "the" pig and of particular ones; their highly variable behavior attracted attention from St. Augustine, Visigothic peasants, eighth-century Irish legislators, and the designers of the Plan of St. Gall. Chapter 2 reconstructs the linkages "from the mud to the cosmos," including an invaluable survey of how natural phenomena figured in Christian hexaemeral literature. It shows Christian intellectuals accepting the dynamism of the "nonhuman world" (61), as well as the limitations in human understanding of its complexities. The third chapter revisits Anna Tsing's idea of "salvage accumulation" that Kreiner deployed in a 2017 Past & Present article, pointing out pigs not only "salvaged" resources their human owners could not get at, but were in turn "salvaged" by early medieval butchers. Here, too, Kreiner stresses the fantastic diversity of conditions in which pigs and people collaborated, even within a single micro-ecology: for instance, at Faragola in northern Apulia, between fourth and eighth centuries completely different ways of inserting humans and pigs into the landscape prevailed (92-95), proving that ecology did not determine agrarian strategies. The penultimate chapter investigates "interspecies relationships" (120), specifically those between pigs and swineherds, pigs and military elites, and pigs and those groups of people who most enthusiastically consumed their flesh. Chapter 5 is about religious readings (Jewish and Islamic, as well as Latin Christian) of "the" pig, as too Roman, or as impure or oversexed, or, ultimately, as good to think about the Incarnation with. In the epilogue Kreiner sketches in some high and late medieval developments in pig history.

A rich and original work, full of fascinating and little-known material, Legions of Pigs is held together by the author's firm belief in early medieval ecological sensibility. Not everyone will agree that the literate or their texts were as environmentally aware as Kreiner makes them out to have been, nor that peasants' "Traditional Ecological Knowledge" had deep taproots in Christian cosmology. And in this study the mechanics of communication between the world of fields and forests and that of scriptoria remain unclear. But the acute discussion of so many particular cases of people-pig entanglement, and the skillful concatenation of disparate sources into a coherent narrative, make up for the book's forthright assertions that sometimes seem to step beyond the available evidence.

One of the advantages of publication in the Agrarian Studies series is its high production standards. The paper is creamy, the fonts elegant, images abound (many reproduced both as good quality color plates in the middle of the book, and as smaller black and white placeholders in the text where the objects are discussed, complete with exhaustive labels), and there are copious maps. The book is also well edited. I noticed few typographical mistakes aside from an "Italia Annonaria" that has slipped across the limes into Mitteleuropa in Map 3, a Murgia plateau that became "Morgia" (93), and ambiguity about the place of Jerash in the episode of the Gadarene swine (on p. 182 the story of Jesus' second exorcism, from Mark 5.1-20, is located either at Gadara or Gerasa, but by pp. 192-193 Gerasa has won out, despite its distance from any sea for the demoniac pigs to leap into). If one has to make do with endnotes in order to win over those "general readers" mentioned in the preface, it is a small price to pay next to the many qualities of this printed artifact. In both form and content, then, Legions of Pigs is a really nice book.