The ‘Silk Road’ was an historically and archaeologically documented cultural phenomenon, characterized by gradually increasing interaction that connected communities in Central Asia to a larger social and economic sphere [1]. Scholars are increasingly exploring the broader process of exchange through Central Asia, including the study of corridors of diffusion from the third millennium B.C. onward and systematic exchange systems of the late first millennium B.C. onward, collectively constituting a wide range of goods and peoples [2, 3, 4, 5]. This cultural arena of interconnectivity tied certain Central Asian populations into a shared realm of commodity transfer, resulting in the spread of material goods over vast distances. Approaching the concept of the Silk Road, it is harder to pin the term down to one time period or cultural phase, especially seeing that scholars have been studying pre-Silk Road exchange in the archaeological record for decades [1, 6, 7, 3]. Furthermore, many of the most important routes of Eurasian exchange transected some of the highest mountain ranges in the world [8]; however, limited archaeological investigation has been undertaken outside the major urban centers at lower elevations [9]. Furthermore, there is still little scientific inquiry into what goods were actually moving along the historical trade routes [10]. We use archaeobotanical data to study what crops were actually consumed at these medieval towns and compare the data to other sites in order to explore the spread of domesticated plants across the ancient world. We suggest that orchards and vineyards around the oasis cities of Central Asia, such as Bukhara, Khiva, Loulan, and Samarkand, provided cultivated goods for merchants and travelers, who in turn carried those fruits and grains along a nodal network and ultimately across two continents. In this article, we synthesize medieval-period botanical data and present a systematic study of botanical remains recovered from anthropogenic sediments from Tashbulak, Uzbekistan (A.D. 800–1100). We also suggest that most of the fruit crops identified in this archaeobotanical assemblage were carried to the site by merchants from lower elevations, based on the fact that many of these trees cannot grow at high elevations. By pulling together these diverse data sets and contrasting them with historical sources, we argue that arboreal crops were a prominent part of the economy across Central Asia during this period and that certain crops dispersed across Eurasia through Central Asia.

The archaeobotanical data that we present in this paper fit into an historical context; in order to interpret these data, we must understand what the historical sources tell us regarding the cultivation of crops in medieval Central Asia. Early literary accounts from Central Asia attest to the fruits of medieval urban markets and the commerce routes that spread them. For example, Abu Hamid al-Andalusi al-Gharnati traveled in Khorezm from 1130–1155 and described cities, villages, farmsteads, and fortresses. He also stated that there were “fruits, the like of which I have not seen in any of the other countries I have visited” ([ 11 ]:88); specifically describing melons, dates, red and white grapes, apples, pears, pomegranates, and watermelons. About a century earlier, in 988, Ibn Hawqal described Khorezm as a “fertile country, producing many kinds of grain and fruit” ([ 11 ]:177). Zahiruddin Muhammad Babur, wrote that “[g]rapes, melons, apples, and pomegranates, all fruits, indeed, are good in Samarkand; two are famous, its apple and its şāhibī (grape)” ([ 12 ]:77). Nuruddin Muhammad Jahangir (1569–1627) repeatedly stated that farmers near Samarkand grew exceptionally sweet apricots, peaches, melons, and apples, as well as rice, millet, and wheat. He specifically noted that “[o]n one tray they brought many kinds of fruit—Kārīz melons, melons from Badakhshan and Kabul, grapes from Samarkand and Badakhshan, apples from Samarkand, Kashmir, Kabul, and from Jalalabad, which is a dependency of Kabul, and pineapples, a fruit that comes from the European ports” ([ 13 ]: Vol. 1:73). Al-Jahiz supposedly wrote a preserved late first millennium pamphlet on trade, which focuses on luxury goods coming into the Abbasid capital of Baghdad [ 14 ]. He extensively discusses fresh and dried fruits as one of the most prominent trade goods. A cache of Sogdian documents recovered from the Mugh (ca. 600–800 A.D.) citadel discuss economic transactions, notably the trade of large amounts of barley grains and wine [ 15 ]. Contemporaneous documents from the region also note the importance of the exchange of dried fruits and even suggest that some people paid their taxes in dried fruits and nuts [ 15 ]. The archaeobotanical data collaborate these historical texts by illustrating that people were moving fruits and nuts and that a diversity of cultivated foods was used in the cuisines of medieval Inner Asia.

Comparative archaeobotanical data

Archaeological studies complement the historical sources by illustrating how diverse economic strategies across Eurasia were at this time, surveys have identified the presence of cities, towns, and small farmsteads [9, 16, 17]. Stable isotope analyses of bone collagen demonstrated highly diverse diets between regions that were narrowly circumscribed within communities across this varied cultural landscape [18]. Examining previous studies of botanical remains from medieval contexts helps us understand how our new data fits into a broader Eurasian dispersal of domesticated trees. These findings are, in most cases, unpublished or hard to access outside Central Asia. While direct dates, photos, and descriptions of the identification criteria are lacking for most of these reports, they merit further consideration. In eastern Kazakhstan, a small archaeobotanical assemblage was collected at the fortified town of Talgar (ca. 700–1200 A.D.; Fig 1); it contained remains of barley (Hordeum vulgare), both naked and hulled forms, broomcorn millet (Panicum miliaceum), and compact wheat (Triticum aestivum) grains, as well as wild seeds, notably Polygonum and Onopordum acanthium [19]. Another small study at the same site was conducted by Miller [20]; the 2.4L of sediment contained free-threshing wheat and barley grains, a possible oat (Avena sp.) grain, and numerous wild seeds and dung fragments. Two additional small samples from the following season (1.0 and 1.5L of sediment) also contained wheat, barley, a possible foxtail millet grain (Setaria sp.), and wild seeds–Chenopodium, Convulvolus, Cyperaceae, Trifolium, Trigonella, Hypericum, Plantago, and Galium [20]. Also in eastern Kazakhstan, three flotation samples (24L of sediment total) from the medieval occupation (1220–1420) at Begash (Fig 1; [2, 21]) were analyzed, containing 45 broomcorn and 11 foxtail millet grains, as well as 1,217 identified wild seeds or seed fragments representing 21 distinct categories of seeds. At Antonovka (Fig 1), 22 flotation samples and 382 liters of sediment from thirteenth century layers were floated [19]. The assemblage consisted of 1,500 wild herbaceous seeds, including Chenopodium, Oenothera, Lithospermum arvense, Rubus, and Anchusa arvensis, and 178 domesticated grains and 80 legumes. Of the grains, 119 were of a highly compact form of wheat, the remainder came from hulled barley and broomcorn millet, and among the legumes, 69 were peas (Pisum sativum), the rest were lentils (Lens culinaris).

Archaeobotanical studies in the Talas Valley of southern Kazakhstan were conducted on sediments from a fortified structure that was excavated at Akyrtas (ca. 900–1200 A.D.) and a mosque at Ornek (Karluk; ca. 900–1200 A.D.), both of which contained domesticated grains of wheat, naked and hulled barley, and broomcorn millet, unspecified legumes, as well as wild seeds of Chenopodium, Lithospermum arvense, and Polygonum. Grape pips (Vitis vinifera; n = 3) and apple/pear seeds (n = 7) were also recovered from Ornek ([19]:99). The nearby site of Kuiruk-tobe provided hand-picked desiccated grape pips and possible watermelon seeds (Citrella lanatus) [19]. In flotation samples from Djuvan-tobe (ca. 600–900 A.D.), Bashtannik [22] identified 178 carbonized specimens: 65 barley grains; 61 broomcorn millet grains; 24 free-threshing bread wheat grains; 14 peas; 4 lentils; and grape pips. The most interesting discovery from the seventh century occupation layers was a single rice (Oryza sativa) grain. He also recovered a single rice grain from sediments from Karaspan-tobe (ca. 300–500 A.D.), as well as a purported plum pit (Prunus sp.), grape pips, peas, and millet, barley, and wheat grains.

At several sites in Ferghana, a Soviet excavation team dissolved unfired mudbrick in water and hand collected large carbonized seeds from within [23]. The mudbricks came from fifth to seventh century layers in the Osh Region at the border of Kyrgyzstan. Barley, both hulled and naked forms, was the most prominent grain from Kuyuk Tepe and Tudai Kalon. Compact and lax-eared forms of wheat were recovered from the sites of Kuyuk Tepe, Munchak Tepe (compact), and Tudai Kalon. Broomcorn millet grains were also recovered from all three of these sites and seeds from a small-seeded form of lentils were recovered from Kuyuk Tepe and Munchak Tepe. Peas and an unspecified vetch (Vicia sp.) were reported from Kuyuk Tepe. Rice grains were also reported from Munchak Tepe, on the Sokh alluvial fan near the Syr Darya River, as were grape pips, peach and apricot stones, and melon and unspecified cucurbit seeds ([24, 23]:176). Papaver sp., although likely wild, and cotton seeds (Gossypium sp.) were recovered from Tudai Kalon and Kuyuk Tepe, as well as a slightly latter (ca. 600-800A.D.) site in the same region, called Ak Tepe [23]. An abundance of capper seeds (Capparis spinosa) was recovered from a burial at Damkul Cemetery, also near Kerkidon [23]. Grapes represent the most prevalent fruit found at Kerkidon, and at the nearby site of Settlement 5a a possible winery was excavated. Wineries have been reported from medieval sites across southern Central Asia [25]. Gorbunova [23] also references a study from the 1970s, where a series of occupation sites and burial grounds in the Asht Region of northern Tajikistan were excavated, hand-picked seeds at those sites supposedly included melons (Cucumis melo), watermelons, unspecified nuts, peaches (Prunus persica), apricots (P. armeniaca), cherries (Prunus sp.), apples (Malus pumila or M. sieversii), and almonds (P. dulcis). An even more interesting series of botanical discoveries came from the 1933 excavations at the fortified citadel at Mugh (ca. 600–800 A.D.) in northern Tajikistan, which is usually associated with Sogdians. Among the handpicked remains of cultivated plants, the excavators noted cherry, peach, apricot, grape, apple, and cotton seeds, grains of hulled barley, free-threshing wheat, broomcorn millet, a large amount of walnut (Juglans regia) and almond shells, and legumes that they claim are fava beans (Vicia faba) [15, 26]. They also claimed to have grains of cultivated Echinochloa crus galli, a weed or loosely domesticated grain that is sometimes allowed to grow or is planted in fields in Tajikistan and Uzbekistan. Yakubov [15] also referred to finds of plum, cherry, peach, and apricot pits, as well as apple and grape seeds from contemporaneous sites in the region around Mugh. Furthermore, Lunina [25] noted the remains of fruits in a well at the southern Sogdian city of Nesef, dating between the eighth and twelfth centuries; these finds include apple, watermelon, cucurbits, and grape seeds, peach and apricot pits, and walnut and almond shells.

One of the largest archaeobotanical study conducted in Central Asia consists of hand-collected plant remains from Bazar-Dara (cliff-market; nearly 4,000masl), Tajikistan [27]. The ancient high-elevation town would have been supplied by caravans from lower elevation farming centers and is roughly contemporaneous with Tashbulak. Bubnova [27] theorized that there would have been steady supply routes carrying fruits, nuts, legumes, and grains to the mining communities at these higher elevations [27]. There are also high-elevation remains of ancient water mills for grain grinding in the Aksu River valley. Among the wide variety of cultivated fruits and grains recovered at the site, the excavators identified wheat and barley as well as one possible rye (Secale cereale) grain [27]. Interestingly, they also report to have found rice, as well as Vicia, peas, and lentils. The range of fruits that Bubnova [27] identified from the site is unparalleled at any other archaeological site in Eurasia, while there are no direct dates on the material, and neither photographs nor morphological descriptions were made, she claimed that the project botanists identified melon (13,112 seeds) and watermelon seeds (n = 246), mulberry seeds (Morus sp.), walnut shells (7,474), other nut shells, apricot and peach pits, almond shells (n = 10,315), apple (n = 975) and pear (n = 10,782) seeds, cherry pits, as well as pits of what she called cherry plums (with over 9,000 pits), pistachio (Pistacia vera) shells, grape pips (supposedly recovering 52,805 from house 2 at the site and over 5,000 from the other contexts), and barberry seeds (Berberis sp.). She also claims to have found a few fruits and nuts that have never been identified in archaeological sites in Central Asia before, but the finds are not impossible to believe given the extent of the trans-Eurasian exchange during this time period, including date pits (Phoenix dactylifera), hazelnut shells (Corylus cf. avellana), persimmon seeds (Diospyros sp.), and most astonishing of all, one coconut shell (Cocos nucifera) and some form of unspecified cucurbit seed, possibly Lagenaria siceraria. It is important to note that there were later occupations at the site and some of these finds could have been recovered out of context.

Merv (Fig 1) was briefly, during the twelfth century A.D., one of the largest cities in the world and arguably the most strategic ‘fueling station’ along the Silk Road. In 1992 and 1993, M. Nesbitt conducted extensive analysis on 1,074 liters of sediment from early medieval layers, comprising 100 samples and 62 discrete deposits. They published a synthesis of the major finds in Herrmann and Kurbansakhatov [28]. Of the 62 contexts that were sampled, 37 contained domesticated plant remains–ubiquities (number of contexts in which the given plant category appears) were provided for the 11 cultivated species recovered. The most ubiquitous was cotton, appearing in 78% of the contexts, followed by hulled barley (46%) and free-threshing bread wheat (38%); broomcorn millet was only represented in 3% of the contexts. Legumes were represented by lentils (24%) and peas (8%). Fruit and nut remains from the site included, grapes (8%), hackberries (Celtis sp.; 8%), melons (3%), peaches (3%), and almonds (3%) [28]. Moving further west, Brite et al. [29] brought together a list of Soviet-period (mostly 1960-1970s) mentions of domesticated crops in archaeological reports. They noted the presence of grapes, millet, and barley as far back as the fifth century B.C., and peaches, Russian olives (Elaeagnus angustifolia), and melons possibly appearing sometime between the fourth century B.C. and the fourth century A.D. They also noted grass peas (Lathyrus sativa), possible oats (Avena sativa), and possible alfalfa (Medicago sativa) by the fourth to fifth centuries A.D. They provided references from an archaeological report from 1966 claiming sorghum (Sorghum bicolor) by the sixth to eight centuries A.D. and rice by the seventh to eighth centuries A.D. Collectively, these data illustrate that cultivation was a prominent part of the medieval Central Asia economy; they also show that fruit orchards were maintained across a large geographic area and crop varieties were dispersed across Eurasia during this period.