THE “WATSON THESIS”

Like the histories of Braudel, Wallerstein, and Hodgson, “The Arab Agricultural Revolution” offers a bold interpretation, or a vision of how things once were, that readers can test from multiple disciplinary angles. What elevates Watson's article high above more ordinary academic writing is its evident relevance outside its immediate disciplinary fields of economic botany or early medieval Islamic history. For what Watson said 40 years ago proved to be applicable in scholarly debates about technological diffusion in pre-industrial societies, the “decline” of Islamic civilization, the relations between elite and peasant cultural systems, Europe's historical Sonderwegin the second millennium CE, the origins of globalization, or the nature of Mediterraneity.

In a mere 25 pages (for an appendix listing “the main primary sources” fills the last two pages, justifying the fact that a “preliminary report of my research” appeared without notes or references), Watson traversed several centuries and regions to suggest the seventh-century unification of Mediterranean, Fertile Crescent, Persia, and swathes of Central Asia by Islam's devotees created unprecedented opportunities for unhindered circulation. What moved across this new “Islamdom” (as Hodgson called it) were not only armies of Muslims, but also ideas and commodities. Among the latter, Watson singled out specialized techniques of cultivation, particularly irrigation, and plants. Watson (Reference Watson1974, p. 9) listed 17 food and fiber crops: rice, sorghum, hard wheat, sugar cane, cotton, watermelons, eggplants, spinach, artichokes, taro root, sour oranges, lemons, limes, bananas, plantains, mangos, and coconut palms.Footnote ² His fusion of plants and the technologies to grow them into a single agronomic “package” was one of his key insights.

According to Watson, most of these plants originated in India, though a few were Persian or had anyway reached the Sasanian Empire when the Arabs discovered them. Except for coconuts and mangos, they could be acclimatized to different environmental conditions within the Caliphate by judicious cultivation, including artificial waterings. Thus, in the space of 400 years, Watson's plants achieved widespread diffusion and became economically significant in many areas where they had been unknown before Islam. This “achievement,” unparalleled before European expansion inaugurated modernity, permitted high and stable agricultural profits. These in turn stimulated a demographic upswing, rather as Malthusmight have predicted, and fed urbanism in the Islamic world. Taken together, these developments amounted to an agricultural revolution, implicitly the equal of the northwest European one in the eighteenth century that textbooks cited as a precursor to industrialization in the same area.Footnote ³ Thus Watson outlined a new way to think about the impact of the immigration of the Arabs into the Mediterranean, and the formation of the Islamic “ecumene.”

Henri Pirenne, the great Belgian economic historian who hypothesized that the major interruption to the flow of Mediterranean history came in the seventh century, with the establishment of an Islamic maritime hegemony that separated north and south Mediterranean shores and isolated Europe from trade in the Inner Sea, had adumbrated Watson's way of thinking in the 1930s (Pirenne Reference Pirenne1939). Watson did not cite Pirenne, but there are intriguing parallels between the “Pirenne thesis” and what we might call the “Watson thesis” (see Havighurst Reference Havighurst1958). Still, it is important to keep in mind that Watson decentered Europe within the historical narrative. While Pirenne was properly Eurocentric in his concerns, to Watson Europe (Islamic Iberia) was really only the (exceptionally well-documented, to be sure) western fringe of a far larger Eurasian and African polity whose internal communications made possible the exchanges he imagined to have been epoch-making.

Watson, who was trained in economics, expanded his familiarity with southwest Asian agriculture working for various private and state development agencies in Jordan, Syria, and Egypt (1960–61, 1979–80, 1983–86). His interest in economic development (and in movements that promised to deliver it, like the Green Revolution) was based on this practice. His interest in west Asia derived from direct experience. “The Arab Agricultural Revolution” of 1974 and its several subsequent incarnations brought together these two intellectual strands in Watson's formation and applied them retrospectively to the period of Islam's foundation.

As a historian, Watson retained some of the assumptions of mid-twentieth century development economics. His demography was classically Malthusian, and the argument that growing populations could stimulate agricultural innovation and improved supplies found little room in Watson's analysis, with its exogenous factor (the “package” of exotic plants) shaking up the otherwise stable situation of the Caliphate (Boserup Reference Boserup1965). His model of linear, cumulative economic growth facilitated by government policies, ignited by the injection of new cultivars into “traditional” rural systems, and stimulated by the removal of trade barriers, can seem optimistic and teleological today (Decker Reference Decker2009, p. 191). The belief that Homo economicus will adopt “useful” innovations when given a chance, in the ninth century or thereafter, is obvious also in the titles of Watson's essays about “imperfect transmission” and “restricted diffusion” of techniques: Failure to accept better techniques is always just that, failure (Watson Reference Watson1994, Reference Watson and Sweeney1995). The sense some admirers of the “Watson thesis” have that his studies are “somewhat dated” emerges from a post-modern impatience with the simpler myths of a bygone period and the cosmology of post-war development science (Waines Reference Waines2003, p. 573).Footnote ⁴

YOU SAY YOU WANT A REVOLUTION

In the 1970s, revolution was in the air. At the 1973 Atlanta meeting of the Economic History Association Watson had entitled his paper “A Medieval Green Revolution,” and he sustained the comparison with the mostly 1960s government sponsored dissemination of “improved” seed crops and cultivation techniques in Asia by adopting that title for a 1981 article reiterating his theory, admitting thatagricultural revolution is “alas” a “hackneyed” formulation (Watson Reference Watson and Udovitch1981).Footnote ⁵ Yet the ethnicized agricultural revolution coined in 1974 prevailed in the long run. Agricultural Innovation, the fullest expression of Watson's thinking on what it is nowadays fashionable to call plant “translocation,” uses it in preference to the colored version, perhaps because by the early 1980s Indian and African agricultural yields no longer generated the same excitement and hope they used to (Watson Reference Watson1983, pp. 123–28; Boivin Reference Boivin, Fuller and Crowther2012).Footnote ⁶

Curiously, the claims of a sudden, even violent change in the way plants moved and people behaved around them did not garner as much attention from Watson's readers as other aspects of his article, and thesis. Most people would find a revolution that took 400 years to happen, as the “Watson thesis” demands, soporific: Revolutions are supposed to be quick, just a few years (as in France in the 1790s) or months (as in Iran in 1979), and be decisive events that leave nothing the same as before. Dribbled out over four centuries, unnoticed by contemporaries, the Arab agricultural revolution looks positively counter-revolutionary. Agrarian change may have different rhythms than political subversion of the kind usually associated with “revolution” (Bernstein and Byrns Reference Bernstein and Byrns2001), but even the original Agricultural Revolution to which Watson linked the phenomena he noticed in 1974 is generally squeezed into a few human generations, canonically 1700–1850.

THE REVOLUTION MOVES BACKWARD

Critics of Watson's hypothesized Arab transformation of Mediterranean and west Asian agriculture who never took issue with his formulation of change as revolution have however focused on the chronology of his plants’ diffusion. Several scholars of the classical Mediterranean, especially archaeologists, have labored to prove that this or that plant from Watson's list of 17 was actually known in the Mediterranean, or Nile valley, long before the Arabs got there. Some well-preserved seeds of “sorghum (Sorghum bicolor), cotton (Gossypium herbaceum) and possibly durum wheat (Triticum durum)” were identified in Roman and late Roman contexts at Qasr Ibrim, a Nile settlement currently just north of the Egyptian border with Sudan: Their excavators thought such seeds, unassuming as they were, undermined claims to revolutionary agency for the creators of the Caliphate (Rowley-Conwy Reference Rowley-Conwy1989, p. 136; see Watson Reference Watson and Udovitch1981, pp. 32–35 and 1983, p. 20). Likewise, the discovery at a few sites in the Aegean of grains that appear to be hard wheat authorized some peremptory dismissals of Watson's argument and concomitant claims that the ancient Greeks and Romans actually cultivated most of the plants in the revolutionary “package” Watson assigned to the Arabs (Decker Reference Decker2009). Durum wheat matters a lot to modern people, because it contains little gluten and is unsuited to making bread. Thus Watson's assertion that it reached western Eurasia thanks to the Arabs was a loud salvo in the pasta wars, the acrimonious debate about the origins of noodles (Watson Reference Watson1983, pp. 22–23 explicitly argued the “high art” of making dried pasta reached Christendom from Islamdom). The reasoning went that if the wheat needed to make pasta arrived with the Arabs, so must have pasta.

Anyone with a palate will appreciate that the stakes in this Gelehrterstreit are higher than in most. But given the vast differences between whatever passed for pasta in Hellenistic times, or the early Caliphate, and a steaming bowl of bucatini all'amatriciana, this search for origins seems sterile. Whether some genetic evidence suggests there was durum in ancient Attica, or not, or if there have been Roman-era palaeobotanical finds in the plateau of Kerak in Jordan, or even if genetic structure and distribution of modern durum cultivars only “fits vaguely” with the idea of Arab influence on the cultivar, are facts tenuously related to the history of “pasta” and, in the end, to the validity of the “Watson thesis” (Sallares Reference Sallares1991, pp. 316–26; Pray Bober Reference Pray Bober1999, pp. 479–80; Oliveira et al. Reference Oliveira2012; Hoppé Reference Hoppé1999; Zohary et al. Reference Zohary, Hopf and Weiss2012, pp. 39–47). Assigning to such a multifarious food as pasta a single source is surely wrong-headed.Footnote ⁷

Another plant on Watson's list that occasioned controversy is, perhaps surprisingly, the artichoke. Again it is classicists who object to any postclassical appropriation of the tasty thistle and insist that the ancients knew and grew it in the Mediterranean area. In complicated arguments about the genealogy of artichokes, their relation to cardoons (another excellent thistle), and the domestication of both, they appeal to new scientific evidence not available in the 1970s to Watson, whose reconstruction relied principally on Iberian agronomic handbooks (the earliest surviving dates to 961). Yet the archaeobotanical tools now used as a matter of course, electronically synthesized, still leave uncertain whether the Romans gobbled artichokes and/or cardoons. A posting on Blogspot entitled “themedievalarabagriculturalrevolution” (8 November 2013), by a certain “andrew watson” offered a spirited electronic defense of Watson's original position on artichokes as both Arab and revolutionary. It stated “genetic research” proves the artichoke was a modification of the cardoon, and that when added to linguistic and historical evidence (the agronomic manuals) there can be no doubt it was a product of the Arab agricultural revolution.Footnote ⁸ Thus, the scientific data invoked by the admirers of classical agricultural traditions has not ended the controversy. The new archaeobotanical tools have yet to achieve more clarity than the old philological ones Watson used in 1974.

It was not just classical scholars who objected to the appropriation of so much botanical glory to the early Caliphate in Watson's publications. In defense of the Persianate world and its claims to have originated some of the crops in the Watsonian package, Peter Christiansen (Reference Christiansen1993, pp. 67–72) argued for the pre-existence in late Sasanian western Eurasia of cotton and sugar cultivation. Christiansen produced some administrative documents to substantiate his case that the Arabs had not significantly expanded the range of those crops in Iraq and Iran, but allowed that perhaps further west, in coastal Syria, Egypt, the Maghrib, and Spain the early Muslims had in fact introduced those plants for the first time in the eighth and later centuries.Footnote ⁹

Such attempts to deflate the Arab agricultural revolution conflate introduction and diffusion of plants. Even if it can be proved that there was a fair amount of (say) cotton grown in Sasanian Mesopotamia, or of Triticum durum in Attica, and that the Arabs did not greatly expand those cultivations there, the “Watson thesis” remains afloat. For it presents the cumulative effect of diffusion across the Caliphate as decisive, and not the micro-regional impact of a particular crop's first arrival or acclimatization. The revolution is in the process of widespread dissemination, not an event of introduction.

Historians of technology have advanced a similar “chronological” critique of the “Watson thesis,” arguing for greater continuity between Roman and Islamic agriculture than Watson allowed. This objection was born together with the original paper, for Thomas Glick, a specialist in medieval Iberia, made it the centerpiece in his published comments to Watson's article(Glick Reference Glick1974, p. 76). Later, an admirably even-handed essay by a team of historical geographers addressed “objectively” Watson's notion that the introduction of new crops in Islamic Iberia during the agricultural revolution necessitated the introduction of new methods of watering. Convinced of the sophistication of Roman hydrotechnology, these researchers indicated that neither the (scanty) literary record, nor the archaeological one, suggest much post-Roman innovation. At most, they conceded, during the Islamic domination of Iberia Roman techniques had been extended somewhat to new territories, but otherwise there was perfect continuity between first and eleventh century irrigated agriculture in the peninsula (Butzer et al. Reference Butzer1985).

In Iberian historiography, the Islamic period can be a prickly topic, and how one conceptualizes the effects of the immigration of Berbers and Arabs, and the attendant Islamicization, in the eighth–eleventh centuries has political valence even today (Trillo San José Reference Trillo San José2005, pp. 164–66). But archaeological studies show that the irrigated landscapes around Valencia or in Andalusia were new, clearly associated with Arab settlement, and offer carbon-dated data to substantiate the point (Trillo San José Reference Trillo San José2005). On the other end of the Romans’ “Very Own Sea” a Jordanian case study, closely analyzed with many technological enhancements, has permitted excavators and surveyors to conclude that the early Islamic propensity for settlement in floodplains and reliance on irrigation was unrelated to any need to acclimatize Indian crops. Rather, the intensified and extended agricultural exploitation of arid zones in that fringe of the Roman Empire had so eroded hillsides that there were no alternatives by the time the Arabs got there (Contreras et al. Reference Contreras2014, p. 42).Footnote ¹⁰

Watson, it seems, had been insensitive to the varied pedology of the Caliphate (Watson Reference Watson1974, pp. 13–14). Early critiques of the “Watson thesis” in fact stressed the heterogeneity of the Islamic “ecumene,” a space whose regional diversity made the impact of agricultural innovation necessarily asymmetrical (Johns 1984). Whether focused on issues of irrigation technology, or soil conservation, the supply of regional case studies correcting the chronological details of the “Arab Agricultural Revolution” and restricting its diffusion is potentially infinite. But such studies have yet to attainthe critical mass to invalidate the argument that something agriculturally new happened overall in the early Caliphate.

Like Pirenne, Watson made an intervention in the historiographical debates about the nature of the transformation of the ancient world or, as it used to be known, the decline and fall of the Roman Empire (see Ward-Perkins Reference Ward-Perkins1997). This is a very big scholarly subject, which helps us understand why so many and such different scholars responded to the intervention (for different assessments of the period's agriculture, see Wittow Reference Wittow1996, p. 55; Moorhead 2014, p. 286). In a monumental history of the Mediterranean region published at the beginning of this century to revisit Braudel's immortal effort, a classicist and a specialist in late antique culture rejected radical ruptures’ relevance to the pre-industrial past. Peregrine Horden and Nicholas Purcell's version of Mediterraneity requires placid changelessness between neolithic and industrial times, no fall of Rome or, for that matter, Arab agricultural revolution. Consequently, their The Corrupting Sea analyzes Watson's idea in extenso, and suggests not only that most of his revolutionary plants had been around for a long time before their supposed migrations, but also that the introduction of a few crops now and then formed a part of the normal exploitative arsenal by which landowners in the Middle Sea appropriated peasant surplus (Horden and Purcell Reference Horden and Purcell2000, pp. 257–63).Footnote ¹¹

However one assesses such an absorption of revolution into bourgeois routine, Horden and Purcell did call attention to an aspect of the Arab agricultural revolution that Watson neglected. In his article Watson acknowledged that the new crops, by needing new cultivation methods, had required an intensification of rural labor (Watson Reference Watson1974, p. 16). Watson observed this intensification in its temporal dimension, showing how many of his plants called for summer farming, and therefore irrigation, when grown in Mediterranean conditions. In effect they forced cultivators to work hard even during the hottest months of the year, a season when, according to Watson, tradition had peasants doing as little as possible. To Watson, this colonization of time was mainly a “rise of productivity.” Yet farmers need strong inducements to expand their workload, and though Watson gestured toward urban demand and human acquisitiveness, he did not fully explain why people able to produce subsistence for a household without the new crops, and without their grueling work regimen, would want to adopt the new ways. The “Watson thesis” proposed an ethnic “Arab” quality of mind, an experimental yen, drove people to try the new cultivations (Watson Reference Watson1974, pp. 21–22). And while Watson maintained that early Islamic societies had reversed trends toward larger estates controlled by fewer people in late Roman and Sasanian Empires, and promotedsmallholding and sharecropping, he tended to highlight elite contributions to and marginalize peasant agency in his diffusion (Watson Reference Watson1974, pp. 29–30, with an Islamicist's early critique in Cahen Reference Cahen1986, p. 218). By inserting agricultural innovation into the age-old mechanisms of exploitation that sustained Mediterranean elites, Horden and Purcell offered a valuable corrective. Even if it did not dismantle the argument that the Caliphate facilitated plant “translocation” that could have deep repercussions in specific regional contexts, The Corrupting Sea usefully re-introduced class relations into the Arab agricultural revolution and the “Islamic mode of production” (Shatzmiller Reference Shatzmiller1993).

FELLOW TRAVELERS: THE MEDIEVALISTS’ WATSON

At the beginning of that other revolutionary decade, the 1960s, the distinguished American medievalist Lynn White Jr. observed that an “earlier agricultural revolution which was equally decisive in its historical effects” as the one launched by “Turnip” Townsend occurred in the early Middle Ages (White Reference Lynn1962, p. 40). His fantastically productive French peer Georges Duby, whose Rural Economy and Country Life in the Medieval West, first issued in French in 1962, is still in print, was more cautious and did not use the revolution metaphor even for developments of 1000–1200. Duby thought “economic development does not proceed at a regular speed but by fits and starts and short-term changes,” and his second monograph on the cycles of the medieval economy spoke of “take offs” rather than orthodox revolutions (Duby Reference Duby1968, p. 61; Duby Reference Duby1973). Yet it is clear that the concept of the Middle Ages as a rupture in European time appealed to post-war medievalists. The “Arab Agricultural Revolution” participated in the Zeitgeist even while shifting attention away from northwestern Europe, where Pirenne had localized it for European medievalists.

Specialists in western European medieval affairs may not cite “The Arab Agricultural Revolution” or Watson's subsequent explorations of his thesis as a matter of course, but they do deploy his ideas routinely (see Epstein Reference Epstein and Prak2000, pp. 41–42). For instance, a fine textbook dedicated to the very beginning of the Middle Ages refers to the circulation of plants within the early Caliphate as proof of the vigor and articulation of the economy there (Moorhead Reference Moorhead2013, p. 286). The rehabilitation of the European Dark Ages as a crucial cultural and economic transition is now a cottage industry. Even without quoting Watson, and without resorting to his exogenous deus ex machina (Indian plants) to kick-start change, recent evaluations of eighth century agricultural production propose pretty much what Watson had hypothesized for Islamdom in 1974: intensification as much as extension of cultivation, and an increasingly acquisitive elite culture, sparked a take-off in which some discern “the origins of the European economy” (Crabtree Reference Crabtree2010; McCormick Reference McCormick2001; Hodges Reference Hodges2012, pp. 116–36). The “Watson thesis” is part of the landscape also in technical studies detailing medieval soil history, with archaeological sampling of dirt apparently proving that cultivators were adept at conserving soil fertility in Islamic Sicily (Egli et al. Reference Egli2013; Corti et al. Reference Corti, Costantini and Dazzi2013, p. 258).

Perhaps because so much of the Islamic agronomic literature Watson analyzed originated in Iberia, some of the most enthusiastic proponents of the “Watson thesis” have been students of medieval Iberia (e.g., Chalmeta Gendrón Reference Chalmeta Gendrón1994). The translation of his book into Spanish may also have helped the diffusion of his ideas (Watson Reference Watson1998). Iberianists pursue Watsonian insights when they test the record for the Arab introduction of citrus fruits to the Pyrenean peninsula (Ramón-Laca Reference Ramón-Laca2003). They go so far as to seek in the bones of medieval domestic animals traces of the early Islamic agricultural revolution, of the increased exchanges, intensifications, and market orientation it occasioned (Pereira et al. Reference Pereira2006; Davis Reference Davis2008). They discuss the flowering of an Islamic garden culture in relation to the new plants Iberians had available through the Islamic “ecumene” (Fairchild Ruggles Reference Fairchild Ruggles2008; Anderson Reference Anderson2013). Though there were some dissonant voices (Aubaile-Sallenave Reference Françoise1984), specialists in fairly esoteric subjects, like the history of literary agronomy or of irrigation in Islamic Iberia, saw the value in Watson's suggestion that the fusty, forgotten texts or bits of earthenware pots they handled could be part of a revolution, important in the grandest scheme of things (e.g., Bolens Reference Bolens1981; Fernández Bermejo and García Sánchez Reference Fernández, Esteban and Sánchez1998; Glick Reference Glick1977, Reference Glick2005).

Students of the medieval Caliphate outside al-Andalus were also among the early adopters of the innovations Watson conjured up (Keddie Reference Keddie1984, pp. 717–78). Whether discussing food in Fatimid Cairo or Almoravid Anadalusia, the extension of sugar cane cultivation in the Mediterranean, the social status of traders and trade in Islamdom, the archaeology of Egypt's Red Sea ports, the politics of dreaming, the rise of Fatimid power, or the impact of epidemics in Islamic societies, orientalists tend to favor Watson's thesis (Lewicka Reference Lewicka2011; Remie Constable Reference Remie Constable1996 and Reference Remie Constable2013, p. 202; Ouerfelli Reference Ouerfelli2008; Van der Veen Reference Van der Veen2011; Lamoreaux Reference Lamoreaux2002; Brett Reference Brett2001; Pamuk and Shatzmiller Reference Pamuk and Shatzmiller2014, p. 216). The counter-argument, most extensively developed by the Viennese-Israeli Islamicist Ashtor, that Islam and its institutions had been an enormous dead hand on Eurasia, stifling cities, industry, trade and economic activity in general, did not make many converts among scholars of medieval Islamdom (Ashtor Reference Ashtor1976). Current orthodoxies lean toward an economically vibrant early Caliphate (with sometimes a “decline” after about 1100, as Watson (Reference Watson1974, pp. 32–35) also accepted). In such reconstructions revolutions à la Watson are very handy explanations of how it all happened (e.g., Shatzmiller Reference Shatzmiller2011). Indeed they are essential building blocks of the intellectual edifice.

THINKING GLOBALLY

Now that Bill Gates has embraced Big History we should expect that historiographic trend to flourish further, supported by his Big Commitment (see www.gatesnotes.com/Education/Bill-Gates-Big-History). Yet the tendency among historians to think big, hemispherically or even globally, began far earlier and took a decisive turn in the 1970s with Wallerstein's Modern World-System. Scholars of the “Great Divergence,” code for the attempt to explain Europe's surprising supremacy over Asia in the last 200 years, of world history or of globalization, all in a sense react to the circumstances of late the twentieth and early twenty-first century life and seek in the past some way to understand them. Contemporary curiosity about connectivity and the circulation of commodities that renders visible such connectivity, particularly within capitalist systems of exchange, can be retrofitted into early modernity (Wallerstein's world-system) or even deeper into the past, as Janet Abu-Lughod did (Abu-Lughod Reference Abu-Lughod1989). Collectively, the world-systematizers, the world historians, the Big Historians, and their allies form a movement in contemporary historiography that sees large caliber comparisons as a satisfactory method of doing historyand considers synthesis of data from disparate places productive (for instance Lieberman Reference Lieberman2003 and Reference Lieberman2009).

As noted earlier, the fortunes of “The Arab Agricultural Revolution” in scholarly footnotes seem to have rallied after 2007, certainly according to Web of Science. While this may reflect the increased ease of tabulating citations as more journals go digital, it also seems related to an unpredictable uptick in the scholarly relevance of the “Watson thesis.” Watson's work was always popular with world historians and in narratives that emphasized large scale, world-systemic trends and changes. Indeed, his work with the widest “global” reach (Watson Reference Watson and Udovitch1981) has enjoyed even more resonance than his original paper, as its reprinting history reveals (in Waines Reference Waines2002). Therefore, it seems reasonable to postulate that recent interest in Watson's publications and in his thesis is related to current fashions among historians and the increased production of world/Big history, especially in English, and interest in transcultural contact. Some early, programmatic publications in these fields relied on and cited Watson as an authority (Bentley Reference Bentley1996, p. 755 and 1998, pp. 247–48; Shaffer Reference Shaffer1994, pp. 1–2, 13–14).

Medieval Europeanists attempting to insert their bailiwick into these larger contexts have likewise found the “Watson thesis” irresistible (R. Moore Reference Moore2003; Ruiz Reference Ruiz2006). Not only did it describe medieval economic dynamism of an almost capitalist type, it also showed how netted together medieval people actually were. Likewise, medievalists working in a comparative vein in order to sort out why European economic productivity surged ahead at the beginning of modernity use Watson's analysis of Islamic farmers’ manuring and soil maintenance practices to distinguish a European agroecology into which large domestic animals were better integrated than elsewhere (Mitterauer Reference Mitterauer2001).

Similarly pondering the origins of modernity, but looking at other geographical contexts, many scholars have discovered and recycled Watson's thesis. Researchers preoccupied with the construction of pre-modern African agriculture and states have found in it a model of how religious affiliation, trade, and trends in the cultivation of crops might work together (Fuller and Boivin Reference Fuller and Boivin2009, p. 30). Atlanticists, perhaps inspired by the brilliant insights of Alfred Crosby and Sidney Mintz (who cited Watson: Mintz Reference Mintz1985, p. 15), track back to the Islamic Mediterranean divined by Watson some of the crops, and patterns of cultivating them, they consider foundational to the Columbian Exchange and the history of their expansive terraqueous region (Boivin et al. Reference Boivin, Fuller and Crowther2012, pp. 455–56). Investigators into the differences between pre-industrial China and other Eurasian polities have been reassured by the westward drift of agricultural innovation charted by Watson, and persuaded (by the stubborn impermeability of northwest Europe to these innovations) that the unequal development of China and Britain since about 1800 had no deep roots or causes.Footnote ¹² Investigators into urban development who try to figure out why western Europe could sustain a metropolis like London in 1700, while Baghdad, formerly the crossroads of the universe, shrank and sank into obscurity, build on Watson's linkage between agricultural productivity and urbanism (Bosker et al. Reference Bosker, Buringh and van Zanden2013, p. 1419). Environmental historians, from the beginning fellow travelers of the global history movement because environment is the easiest thing to assess across cultures (since all societies had one), are mesmerized by the ecological fallout from the plant “translocations” Watson envisioned, and the attendant social and cultural change (Headrick Reference Headrick, McNeill and Maudlin2012, pp. 40–41; Burke III Reference Burke, Burke and Pomeranz2009a, pp. 38–39 and Reference Burke, Burke and Pomeranz2009b, pp. 86–88). Also academics who wonder where capitalism came from, and whether the widespread dissemination of goods and people (and, we should add, microbes) characteristic of the free market economy existed before industrialization and Europe's colonization of much of the rest of the world, can turn to Watson for guidance (J. Moore Reference Moore2003, p. 147; Banaji Reference Banaji2007, pp. 60–62; Kick and McKinney Reference Kick, McKinney, Babones and Chase-Dunn2012, p. 394).

In sum, without intending to, Watson wrote an article in 1974 that prefigured some of the salient preoccupations of historians 25–40 years later. His argument for the connections between politics, technologies, and trade networks, applied to that very large slice of the pre-modern world called the Caliphate, has seemed persuasive to people working in heterogeneous fields of inquiry but interested in past linkages and patterns at the macroscopic scale. The Arab agricultural revolution reached extensive unexpected audiences.

IS THE REVOLUTION OVER NOW?

The concision and elegance of “The Arab Agricultural Revolution,” as well as its manifest usefulness on so many historical agendas, go a long way toward justifying the article's enduring popularity. Since Watson repeatedly breathed new life into his creature, turning that Frankenstein into a “thesis” through a half dozen articlesand a monograph elaborating his key tenets, “The Arab Agricultural Revolution” soon transcended the pages of the Journal that first hosted it. Whether the article, and thesis, have aged well, deserve this popularity, and remain persuasive under scrutiny is very much a matter of opinion and, as this essay has shown, of historiographical orientation. But the staying power of Watson's presence in debates among quite disparate historians might suggest that in fact in 1974 he had struck on a genuinely groundbreaking interpretation.

For it was an interpretation of a period, macrohistory packed into a short essay, and merits consideration as such. Others before Watson, in nineteenth century Spain or mid-1940s France, had already noticed the role that the Caliphate played in extending the cultivation of certain plants in the Mediterranean and western Asia (García Maceira Reference García Maceira1876; Haudricourt and Hédin Reference Haudricourt and Hédin1943, p. 130). Watson leavened the insight by working it into a model for the transformation of medieval societies. His thesis does not depend on the close investigation of the introduction into one or another region of any specific plant; it is diffusion and normalization that form the kernel of Watson's argument. His revolution is a gradual, admittedly uneven spread across western Eurasia of a diverse “package” of plants. For this reason the discovery that there were places where some of these plants had been known in pre-Islamic times does not disprove the thesis.

But the flexibilityof the argument does not render the staying power of the “Watson thesis” any less astonishing. In the last two decades, economic botany and ethnobotany, the sciences that track the movements of plants within economies and cultures, have undergone a revolution of their own. The development of new techniques and the application of new technologies for gathering and analyzing botanical remains in archaeological sites has led to an exponential growth in publications on, and arguable in knowledge of, past plants. The geographical distribution of this knowledge is uneven, and some periods (notably the Neolithic) get more attention than others. Regardless, the cumulative effect of these researches has been transformative. Compared to the 1970s, the quiet, secluded subfield in which Watson situated his contribution is now volcanic.

Watson worked virtually without archaeology (pace Keddie Reference Keddie1984, p. 734). He founded his discussion of his 17 plants that had revolutionized agricultural production between the eighth and twelfth centuries on a meticulous parsing of agronomical manuals written inside the Islamic “ecumene” (many in its westernmost territory). This elite literature, written by and for the ruling class, was not at all consistent in its empiricism, though some of its modern readers, like Watson, considered it limpid proof of progress (Bolens Reference Bolens1977). Watson mined these books for the data they contained, though he then translated this traditional, philological reading into the very wide ranging hypothesis discussed above. Surprisingly, his old fashioned reconstruction of what really happened in the gardens and fields has not been decisively undermined by the cutting edge archaeobotanical research of the past 20-odd years. The “Watson thesis” is not about the history of individual species, of course, yet the genetic make-up of Sorghum bicolor in the western Mediterranean, for example, seems to confirm what the medieval agronomists’ ink on parchment and paper had suggested to Watson so long ago (Medraoui et al. Reference Medraoui2007). Similarly, the 2006 discovery of remains of twelfth-century spinach in a Pyrenean village adds another dimension to the argument about Arab diffusion advanced in 1974 (Hallavant and Ruas Reference Hallavant and Ruas2014). Such unpredictable congruence between current archaeobotany and many of Watson's 1970s findings gives hope that the revolution is not over yet.