We present a stable isotope study on ancient plant remains from the Tibetan Plateau to explore the cultivation strategies employed by herding communities during the 1^st millennium BCE and 1^st millennium CE. Through carbon and nitrogen stable isotope analyses of 6-row barley (Hordeum vulgare) grains recovered from three sites, representing some of the oldest evidence of grain cultivation in the region, we inquire whether these early highlanders developed intensive cultivation activities in environments optimal for transhumant animal pasturing. We further investigate the influence of growing conditions on barley grain size. Our results from Piyang, Dingdong, and Jiweng provide critical insight into early barley cultivation and labor strategies in western Tibet.

Research shows that this region was at a major crossroad of the trans-Eurasian exchange of crops and livestock, among other commodities, situated along a southern route of the eastern dispersal of the Fertile Crescent cereals, particularly barley (Hordeum spp.) (Liu et al., 2017; Lister et al., 2018; Gao et al., 2021). This route parallels (albeit a millennium later) the well-documented northern route through the Inner Asian Mountain Corridor, a series of foothill locations linking today's eastern Kyrgyzstan, Uzbekistan, and Kazakhstan and western Xinjiang, which were intensively utilized by ancient communities between the 3^rd and 1^st millennium BCE (Frachetti et al., 2010; Jones et al., 2016; Liu et al., 2019). The Eurasian food globalization process involved agropastoral communities across Inner Asia cultivating and transporting Southwest Asian crops such as free-threshing wheat (Triticum aestivum/durum) and barley and managing livestock such as sheep (Ovis aries), goat (Capra hircus), horse (Equus caballus), and cattle (Bos taurus). The spread of broomcorn (Panicum miliaceum) and foxtail millet (Setaria italica) from their domestication center in northern China westwards to Central Asia and beyond occurred during the 3^rd and 2^nd millennium BCE (Liu et al., 2018; Hermes et al., 2019; Dal Corso et al., 2022; Endo et al., 2023). Recently published stable isotope results, ceramic impressions, and genetic analyses on related materials are beginning to reveal evidence signifying the incorporation of these newly imported crops and livestock into the indigenous culinary and cultural traditions (Liu and Reid, 2020; Vaiglova et al., 2021; Li et al., 2022; Murakami et al., 2022; Ritchey et al., 2022; Tian et al., 2022; Endo et al., 2023; Sun et al., 2024a).

In recent years, there has been an increase in research in the western and central Tibetan Plateau that includes archaeobotanical recovery as one of the primary objectives of study. This resulted in new insight into human and plant interactions that manifested themselves in distinct subsistence strategies, cooking traditions, and ecological interactions. While maintaining these distinct traditions, communities in western and central Tibet were interconnected with broader Eurasia (e.g., Chen et al., 2023; Gao et al., 2021; Tang et al., 2021; d'Alpoim Guedes et al., 2014; Lu et al., 2021; Song et al., 2018, 2021). The Tibetan Plateau provides a unique window into understanding human ingenuity and persistence, as its high elevation presents particular challenges to human occupation, such as limited growing seasons, harsh weather systems, and reduced oxygen availability.

Indeed, humans utilized varying and innovative subsistence strategies to succeed in the high elevations of the Tibetan Plateau. Pastoralism and arable agriculture were first introduced to the eastern Tibetan Plateau between the 4^th and 2^nd millennium BCE. Domestic pig (Sus scrofa) and millet farming spread into the region from the Loess Plateau and were first concentrated along the northeastern margins of the Plateau (Aldenderfer, 2011; d'Alpoim Guedes et al., 2014; Chen et al., 2015; d'Alpoim Guedes and Aldenderfer, 2020; Ma et al., 2023). Archaeobotanical assemblages from before 1,500 BCE are dominated by foxtail and broomcorn millet, which predate the introduction of wheat (Triticum sp.) and barley (Hordeum sp.) into the region (Chen et al., 2015; d'Alpoim Guedes, 2015). A different strategy was used in southeastern Tibet. At the sites of Karou and Xiaoenda, for example, there has been evidence of mixed hunting and millet farming (Zhang et al., 2019; Song et al., 2021; Lu, 2023). Questions remain as to whether millet grains could be brought to high elevations from lowland farms via trading networks. Macrobotanical remains from the sites of Zongri and Karou support both sides of the argument (Ren et al., 2020; Song et al., 2021). However, human isotope values from Zongri show clear evidence of substantial millet consumption, likely occurring daily (Cui et al., 2006). While grain trade cannot be ruled out as an explanation, it is unlikely that such trade could sustain human food at a population level, raising questions about local cultivation. By the mid-second millennium BCE, the Southwest Asian domesticates such was wheat, barley, cattle and sheep/goats were introduced to various Tibetan regions (Chen et al., 2015; d'Alpoim Guedes, 2015). The hardiness of barley and ecological flexibilities of sheep/goats, yak (Bos grunniens) and yak-cattle hybrids likely contributed to the flourishing of agropastoral communities in regions higher than 2,500 meters above sea level (masl hereafter) (Chen et al., 2015, 2023; Zhang et al., 2022; Tang et al., 2023).

On the other side of the Plateau, communities in western Tibet were likely closely connected with cultural groups in the Kashmir region as well other regions on the Plateau (Spengler, 2015; Spate et al., 2017; Chen et al., 2024). As early as 2,600 BCE, Harrapan communities cultivated a diverse crop package including hulled 6-row barley (Horduem vulgare var. vulgare), wheat (Triticum aestivum and sphaerococcum), field-pea (Pisum arvense), and rice (Oryza sativa) (Pokharia and Saraswat, 2002; Pokharia et al., 2011). In northern Nepal (3,000–4,000 masl), between 1,000 BCE and 1,000 CE, there was an early 6-row barley and buckwheat (Fagopyrum esculentum/tatarieum) dominated agropastoral system, with later inclusions of bread wheat (Triticum aestivum), broomcorn millet, and pea (Pisum sativum) (Knörzer, 2000). Similar ceramic traditions of cord decorations found across the Himalayas may also support this interconnectivity (Chen et al., 2024). By 1,500 BCE in central Tibet, agropastoral communities at Changguogou (1,400–800 BCE, 2,750 masl) and Bangga (1,000–800 BCE, 3,750 masl) had hulled and naked (Hordeum vulgare var. nudum) barley, bread wheat, pea, and probably buckwheat (Fu, 2001; d'Alpoim Guedes et al., 2014; Liu et al., 2017; Tang et al., 2021). In southeast Tibet, Wang et al. (2021) show that the Nyingchi Region was connected to agropastoralist communities to the west, through the presence of bread wheat, 6-row barley, and peas dated to the 1^st millennium BCE. In addition to the three western Tibetan sites presented in this study, the large site of Kaerdong (455–700 cal. CE, 4,300 masl) has evidence for a barley-dominated agropastoral system, with the addition of bread wheat and buckwheat (Song et al., 2018). This rapidly growing dataset suggests a possible southern introduction of domesticates into central and western Tibet (Laurent, 2015; Stevens et al., 2016; Liu et al., 2017; Lister et al., 2018; Gao et al., 2021). This paper begins to address the actual methods used by communities to successfully grow Southwest Asian crop domesticates on the Plateau by examining the labor choices involved in plant cultivation, as measured through stable isotope values of the barley grains themselves at three small agropastoral sites in the Tibetan highland.

Crop management, such as irrigation and manuring, require high labor investment and integration with other tasks, especially in mixed agropastoral economies where mobility for at least some of the population is necessary (Lees and Bates, 1974). There is a potential opposition between the labor strategies necessary for plant cultivation and those of animal pastoralism, particularly in landscapes that lend themselves to herding activities, such as the Tibetan Plateau highlands. Pastoral systems use extensive labor strategies, where productivity is measured by the access to and quality of expansive pasture and the size of the herds grazed on them. Risks are mitigated through herd and grazing land management (Boserup, 1965; Khazanov, 1983; Barfield, 1999; Halstead, 2000; Kradin, 2015). In contrast, with arable farming, production is limited by the amount of suitable land available and its fertility (Boserup, 1965). In this context, intensification is measured by the amount of labor and resources invested per unit area of land through activities such as irrigation, plowing, and fertilizing to buffer against future food shortages (Boserup, 1965; Morrison, 1994; Halstead, 2006, p. 45). Extensification, within the farming context, uses larger plots of land, spreading labor, energy, and time across increasing area (Halstead, 1995, 2000). Macrobotanical remains and plant stable isotope values are useful proxies for measuring labor strategies and provide an exceptional opportunity to examine the under investigated character of plant cultivation in Western Tibet.

The trans-regional movements brought exotic food items to not only novel environments but also new cultural settings with their own food preparation techniques. Research across Eurasia identifies distinct cuisines and associated cooking traditions that were formulated before domestication and within which domestication occurred (Sakamoto, 1996; Fuller and Rowlands, 2009, 2011). As the cereal crops moved across Eurasia and into new cuisines, selective pressures modified traits apparent in the grains. For example, during the eastward movement of bread wheat and barley into ancient China, there was a dramatic decrease in grain size as the crops entered a boiling-and-steaming tradition that favored smaller grains (Liu et al., 2016; Ritchey et al., 2022). The Asian millets, on the other hand, grew in seed size as they move westward into new banking and grinding culinary traditions (Sun et al., 2024b). Ritchey et al. (2022) argue that the 6-row barley in Tibet, when compared to the other regions in Central and East Asia, are notably larger and attribute this to a historical tradition of a boiling-free roasting zone in high-elevation Tibet. Boiling whole grains is inefficient in time, labor, and fuel at such high altitudes where low vapor pressure reduces the boiling point of water to 86°C at 4,600 masl. A similar trend is seen in foxtail millet on the Plateau (Sun et al., 2024b).

An alternative hypothesis to increased grain size could be increasing investment in growing conditions to produce a higher yield with larger grains. Anthropogenically enriched growing conditions can enlarge grain sizes (Savin and Nicolas, 1996; Altenbach et al., 2003; Dupont and Altenbach, 2003; van Bommel et al., 2021; Larsson and Bergman, 2023). Poor ecological conditions, on the other hand, have been hypothesized to limit plant development and grain size (Fuller et al., 2017; Motuzaite-Matuzeviciute et al., 2018; Motuzaite Matuzeviciute et al., 2021). Experimental work shows variable but generally positive correlations between increased water availability and soil nutrition and grain size in various cereals (van Bommel et al., 2021; Larsson and Bergman, 2023). Within the context of this growing research, we consider this hypothesis through the analysis of grain size and stable isotope values from three Tibetan Sites in the larger Tibetan dataset from Ritchey et al. (2022).

Plant stable isotope values are currently the most direct method for investigating past growing conditions of plants. In semi-arid/arid environments such as in our study area (< 450 mm/annual rainfall), non-native water-demanding cereals are expected to experience water stress to a certain degree (Li et al., 2022). Carbon isotope values (δ¹³C) of plant remains, particularly C₃ plants like barley, reflect the water availability during plant growth and the grain-filling period (Farquhar et al., 1989; Araus et al., 1997, 1999; Wallace et al., 2013). δ¹⁵N values allow for the assessment of soil ¹⁵N enrichment processes during plant growth caused by natural and cultural factors including aridity, soil denitrification, and fertilization through middening and manuring (Bogaard et al., 2007; Fraser et al., 2011; Styring et al., 2018). Together, these measurements allow for a direct assessment of past crop agricultural activities of watering and soil maintenance, which have been used to investigate early crop management strategies in the Middle East, Europe, East Asia (Bogaard et al., 2013; Vaiglova et al., 2014a; Styring et al., 2016b, 2018; Li et al., 2022), and recently in the eastern Tianshan Mountains of Inner Asia (Tian et al., 2022). In this study, we use this method to analyze 55 total barley grains from the sites of Dingdong, Piyang, and Jiweng, with each sample representing a single grain (Table 1).

Water availability during photosynthesis directly influences a C₃ plant's ability to assimilate CO₂, which exists in lighter ¹²CO₂ and heavier ¹³CO₂ forms. When plants are well watered, there is free passage of CO₂ through the open stomata on the leaves and the lighter ¹²CO₂ is preferentially assimilated while the heavier ¹³CO₂ is discriminated against (O'Leary, 1988; Girolamo et al., 2014). When growing in water-limited soils, plants periodically close the stomata to preserve plant moisture, causing CO₂ to be recycled, resulting in higher assimilation of the heavier ¹³CO₂ (O'Leary, 1988; Girolamo et al., 2014). A more negative δ¹³C value of an archaeological grain thus reflects higher water availability during the grain-filling growth period compared to a crop that grew in drier soils (Farquhar et al., 1989; Araus et al., 1999; Wallace et al., 2013). Stable carbon isotope values are typically reported as δ¹³C. However, to compare the values across distinct chronological periods (when the carbon isotope composition of atmospheric CO₂ differed) a conversion to Δ¹³C is needed. This value captures the degree to which a plant discriminated against ¹³C irrespective of the atmospheric composition (Farquhar et al., 1989). We use Δ¹³C_plant−air values as the calculated ¹³C discrimination independent of source CO₂ computed with the equation developed by Farquhar et al. (1989):

After the conversion of results into Δ¹³C, the directionality of the water availability changes, with higher Δ¹³C values corresponding to wetter soils. Elevated Δ¹³C values may reflect the use of watering practices such as man-made irrigation, terracing, or strategic planting in wetter soils (Araus et al., 1999; Ferrio et al., 2005; Wallace et al., 2013).

The productivity of the cereal crop can also be improved through the management of soil nutrition. In particular, anthropogenic fertilization of soils, accomplished in ancient times primarily through dung manuring but also through the application of guano and marine biofertilizers, can be detected using δ¹⁵N values (Szpak et al., 2012; Gröcke et al., 2021). Plant nitrogen isotope values (δ¹⁵N) reflect the isotopic composition of the nitrogen (N) source. For N non-fixers like the barley analyzed in this study, nitrogen is primarily absorbed from the soil. Any enhancements made to the soil, whether of natural or anthropogenic causes, are reflected in higher δ¹⁵N values of the plant remains (Ambrose, 1991; Bogaard et al., 2007; Fraser et al., 2011; Girolamo et al., 2014; Szpak, 2014). Natural causes for heightened δ¹⁵N values include aridity, salinity, and denitrification (Ambrose, 1991; Hartman and Danin, 2010; Szpak et al., 2013). Anaerobic soil conditions and high temperatures can cause soil denitrification which leads to soil bacteria consuming the available oxygen from nitrates, resulting in an increased δ¹⁵N value of the soil (Farrell et al., 1996; Hartman and Danin, 2010). Temporary waterlogging in floodplains or wadi slopes can result in elevated δ¹⁵N values of plants grown there (Hartman and Danin, 2010). High-elevation environments, such as the Tibetan Plateau, have unique impacts on δ¹⁵N values of both the soil and vegetation (see below). Anthropogenic activities to improve fields elevate plant δ¹⁵N values above the natural baseline, with values above 6 ‰ in European and southwest Asian contexts reflecting intensive manure application (Bogaard et al., 2007, 2013; Fraser et al., 2011; Szpak, 2014).

Regionally specific nitrogen isotope baselines can be estimated using archaeological remains of animals that subsist on natural vegetation (such as wild herbivores) (Vaiglova et al., 2022). Based on an estimated trophic offset between diet and consumer tissue, herbivore tissues are approximately 3‰−5‰ higher compared to the values of their diet (Deniro and Epstein, 1981; Minagawa and Wada, 1984). Thus, measured δ¹⁵N values from bone collagen of archaeological herbivores in the region can provide a local baseline against which the archaeological plant δ¹⁵N values can be compared. There are limitations to using local archaeological herbivores to reconstruct baselines, as the δ¹⁵N values can vary between individuals, species, and habitat (e.g., hot/dry vs. cool/wet habitats) but similar limitations exist when using modern plant isotope values (environments change over time and are a product of ancient human and natural processes that can influence soil compositions) (Deniro and Epstein, 1981; Ambrose, 2000; Vaiglova et al., 2022). Unpublished data on archaeological Tibetan deer provide a mean δ¹⁵N of 4.3 ‰ (n = 12) (Tang, 2024). When calculated with the known offset between trophic levels, this provides a baseline plant δ¹⁵N threshold of 0‰−1.3‰. Reported δ¹⁵N values of modern wild vegetation record a mean of 2.4‰ (Yang et al., 2013). We expect the natural non-manured soil δ¹⁵N values to be approximately between 0‰ and 2.4‰.

Results of Δ¹³C and δ¹⁵N analyses are reported in Table 3 and displayed as boxplots and CIs in Figure 3. We use a 95% confidence interval for all analyses. The Δ¹³C values of grains from Jiweng record the highest mean (16.7‰, [16.1, 16.9], n = 19), followed by Piyang (16.2‰, [15.7, 16.6], n = 9), and Dingdong (15.8‰, [15.5, 16.1], n = 27). With the adjusted watering bands for a high-elevation atmospheric effect, all three sites have grains that measure above the optimal watering threshold. Four grains from Dingdong measure below the OWT and four from Jiweng measure above the SWT. Overall, the most observable difference in Δ¹³C values between sites lies in the higher Δ¹³C values from Jiweng. The mean difference between Jiweng and the combined values of Dingdong and Piyang is −0.6‰, [−1.1, 0.0] (Supplementary Table 3, Supplementary Figure 3). This suggests that, given the small sample size of the data collected, the mean difference between the Δ¹³C values at Jiweng and the other two sites is plausibly anywhere between −1.1‰ and 0.0‰. There is some overlap between the CIs of the values from Jiweng and the Dingdong/Piyang data. This suggests that there is possible difference between the mean values of the two sets of groups. The difference is more notable between Jiweng and Dingdong than any other pairing, with a mean difference of 0.9‰, [0.3, 1.5]. This suggests, given the small sample size of the data collected, the difference between the mean Δ¹³C values at Jiweng and Dingdong is plausibly anywhere between 0.3‰ and 1.5‰. There is no overlap between the CIs of the values from Jiweng and Dingdong, suggesting that there is a notable difference between the higher mean values of Jiweng from that of Dingdong.

Dingdong grains have the highest mean δ¹⁵N of the group (16.6‰, [15.9, 17.4], n = 27), followed by Piyang (14.2‰, [12.9, 15.5], n = 9), and Jiweng (13.5‰, [12.5, 14.4], n = 19). All are well above the calculated natural baseline of 0‰−2.4‰ from archaeological herbivores and wild seed remains (Yang et al., 2013; Tang, 2024). When compared to experiments conducted in modern farm settings in England and Germany, where heavily manured (+35 tons of manure/ha) barley and wheat had a mean value of 8‰ δ¹⁵N, all barley grains from this study fall well above this highly-manured threshold (Bogaard et al., 2013). Overall, the most observable difference in δ¹⁵N values between sites is the increased mean of Dingdong. The mean difference between Dingdong and the combined values of Jiweng and Piyang is −2.8‰, [−3.9, −1.8] (Supplementary Table 4, Supplementary Figure 4). This suggests that, given the small sample size of the data collected, the mean difference between the δ¹⁵N values at Dingdong and the other two sites is plausibly anywhere between −3.9‰ and −1.8‰. As the lower limit of the CI for Dingdong is 15.9‰, and the upper limit of the CI for the combined Jiweng/Piyang data is 13.1‰, this difference is notable due to the lack of overlap between the groups. Further, when compared to a similar archaeological plant stable isotope study in Xinjiang, China, the samples from this study, while variable, fall above Li et al. (2022)'s calculated threshold for high nutrient-rich soil condition of 8.5‰ δ¹⁵N for a region (Zhuanglang county) that receives a mean annual precipitation of 550 mm.

At Dingdong, we analyzed both hulled and naked grains. CIs show no notable difference in the Δ¹³C values between naked (15.6‰, [15.3, 16.1], n = 19) and hulled grains (15.9‰, [14.5, 17.2], n = 8) with a mean difference of 0.1‰, [−0.6, 0.8] (Supplementary Table 5, Supplementary Figure 5). Mean δ¹⁵N values of naked barley (17.0‰, [16.1, 17.8), n = 19) are higher than those of hulled barley (15.9‰, [14.5, 17.2], n = 8), with a mean difference of 1.1‰, [−0.5, 2.7] (Supplementary Table 5, Supplementary Figure 5). Given the limited sample size, the difference between δ¹⁵N values of naked and hulled barley at Dingdong is plausibly anywhere between −0.5‰ and 2.7‰. However, there is considerable overlap in CIs between the two groups, suggesting there is not a meaningful difference for either Δ¹³C or δ¹⁵N.

Barley grain sizes at Piyang, Jiweng, and Dingdong are on average very large, in length and breadth, when compared to other archaeological grains in central and eastern Eurasia (see Ritchey et al., 2022 for a robust regional analysis). However, the individual grain metrics vary and span the spectrum of domesticated barley grain size, from the shortest at 4.03 mm to the longest at 7.01 mm (Supplementary Table 1). Figure 4 presents scatter plots of Δ¹³C and δ¹⁵N values vs. grain length, breadth, and thickness. We assessed linear correlations of length, breadth, thickness, and length/breadth ratio vs. stable isotope value using Pearson's r (Supplementary Table 6). However, due to the small sample size, correlation cannot be estimated with much precision. Overall, the results of the Pearson's r suggest poor correlation between grain metrics and isotope value. Two correlations of Piyang grains have Pearson's r that suggest moderate correlation:δ¹⁵N vs. thickness, r₍₇₎ = 0.55, n = 9 [−0.21, 0.88] and δ¹⁵N vs. breadth, r₍₇₎ = 0.46, n = 9 [−0.32, 0.85]. However, the wide confidence intervals suggest that the estimates of the true correlation have low precision and could be anywhere from −0.21 (suggesting poor negative correlation) to 0.88 (suggesting strong positive correlation) for δ¹⁵N vs. thickness and anywhere from −0.32 (suggesting poor negative correlation) to 0.85 (suggesting strong positive correlation) for δ¹⁵N vs. breadth. At Dingdong, both hulled and naked barley were analyzed. Hulled grains at Dingdong are generally narrower in breadth and shorter in thickness than the naked barley (Table 3). When analyzed separately, there are two correlations that suggest moderate positive correlations: δ¹⁵N vs. breadth, r₍₆₎ = 0.42, n = 8 [−0.43, 0.86] and Δ¹³C vs. breadth, r₍₆₎ = 0.47, n = 8 [−0.38, 0.87] (Supplementary Table 6). Additionally, one correlation suggests a moderate negative correlation: Δ¹³C vs. L/B ratio, r₍₆₎ = −0.51, n = 8 [−0.89, 0.33] (Supplementary Table 6). The large confidence intervals indicate that the true correlations have low precision for each of these analyses. All other correlations fall below a Pearson's r of 0.4.

Stable isotope analyses of ancient crop remains allow for the assessment of their growing conditions (e.g., Ferrio et al., 2005; Fraser et al., 2011; Styring et al., 2015). In certain anthropogenic contexts, elevated carbon and nitrogen isotope values (Δ¹³C and δ¹⁵N) could indicate dedicated labor input to both watering (through irrigation activities) and manuring, which in normal circumstances, correspond to agricultural intensification rather than extensification (Bogaard et al., 2013). In an agropastoral setting, relatively lower labor input in watering and manuring could signify a de-emphasis on cultivation activities. Within communities focused more on herding practices for food production, crops may be grown opportunistically and/or extensively, as seen archaeologically in Tian et al. (2022). This study measured and calculated the Δ¹³C and δ¹⁵N of barley grains from the western Tibetan Plateau sites of Jiweng, Dingdong, and Piyang. The results indicate a managed crop cultivation system, where ancient herders invested time, energy, and labor into cultivating barley in the high-elevation western Tibetan Plateau. Furthermore, in considering the role that culinary traditions play in barley grain metrics (Ritchey et al., 2022), we presented a comparison between grain metrics and grain isotope values (Figure 4). No obvious relationship has been observed. Due to the small sample size, we are unable to make meaningful interpretations from the data. The relatively recent inclusion of systematic macrobotanical sampling on the Tibetan Plateau inhibits a larger analysis at this time. Future work will no doubt expand our understanding of early agricultural labor strategies when isotope analysis with a larger assemblage of macrofossils becomes available, which will increase the precision of mean Δ¹³C and δ¹⁵N estimates of ancient crop remains in the study area.

In this paper, we analyzed the stable carbon and nitrogen isotope values of barley grains recovered from three western Tibetan sites: Piyang, Jiweng, and Dingdong. The results suggest that when barley was first introduced into the region, the communities used a shared intensive cultivation strategy to successfully grow barley above 4,000 masl. Agropastoralists at Jiweng, Piyang, and Dingdong likely manured their fields for barley cultivation. Communities at Piyang and Jiweng provided additional water to the crops, either by irrigating the plants or strategically planting at locations with higher soil water retention. The community at Dingdong did not supplement watering for their barley as much as the other two sites but still ensured adequate water for their barley. Further work on the wild taxa to identify possible arable weeds to the genus and species level would add additional information regarding cultivation strategies that could be compared to the isotopic results.

At a broader regional level, our results resonate with the farming systems commonly seen in prehistoric northern China, where early farmers invested labor significantly into the cultivation of wheat, barley, and foxtail and broomcorn millet (Sheng et al., 2021; Li et al., 2022). Our results, however, differs from the extensification trend later seen in northern China and in eastern Tianshan that has been recently documented by isotope analysis (Tian et al., 2022). Additionally, we compared the isotopic results with the morphometrics of the barley grains to ascertain the role of growing conditions in grain size. We did not find any meaningful correlation between isotopically inferred growing conditions and barley grain metrics. Admittedly, the sample size is small, but already at the limit of destructive work allowed due to the limited number of grains recovered. When the opportunity arises, future isotopic and archaeobotanical work with a larger sample size can clarify the trends observed in this study.