An understanding of the exploitation of animal resources is crucial to our appreciation of ancient subsistence strategies, land use, and regional social transformations (Crabtree, 1990; Zeder, 1991; Lhuillier and Mashkour, 2017). Zooarchaeology in Northern China has been consistently applied to the study of ancient remains, with the aim of understanding faunal temporal and spatial distribution, past environments and human-animal relationships (Yuan, 2015). Systematic studies on ancient domestication (Huang, 2010), regional trajectories (Flad et al., 2007; Yuan et al., 2007), secondary products (Li et al., 2014a; Li et al., 2014b; Brunson et al., 2016) and craftsmanship (Campbell et al., 2011; Hou et al., 2018) have been largely centered in the Neolithic and dynastic periods in the Central Plain (Huang, 2000; Li, 2011a; 2011b; Li et al., 2014a). Limited work has been done in other contexts, including Bronze Age Central Shaanxi, which has to date obfuscated the economic conditions underpinning the emergence of the Zhou as a political authority in the late 11th century BCE (Yuan, 2000; Zhongguo Shehui Kaxue Xueyuan Kaogu Yanjiushuo, 2007; Li et al., 2019, Li et al., 2020).

The Proto-Zhou Culture (ca. 1400–1050 BCE) refers to the cultural complex created by the Zhou people and their alliance in Northwest China before the formal establishment of the Zhou Dynasty (1050–256 BCE). In other words, it indicates the dry-farming communities that inhabited the central Loess Plateau during the late Shang Dynasty (1600–1050 BCE) (Huang et al., 2003; Cao, 2007). Epigraphic sources have consistently been used to identify the ancestral land of Zhou, the dominant idea being that it was located in the northern and middle reaches of the Jing River (Khayutina, 2020). According to written sources and inscriptions, the main Proto-Zhou centers include the Zhouyuan region, which encompasses present-day Qishan and Fufeng Counties, and Feng and Hao, located on the western and eastern banks of the Feng River, near Xi’an. Their location is supported by archaeological evidence (Zhang and Yin, 2004; Khayutina, 2010). The earliest Zhou centers, Tai, in the valley of the Wei River, and Bin, in the middle reaches of the Jing River, have not been precisely identified, although most scholars have located the Ancient Bin Area (Gu Bin di 古豳地) in a region roughly covering the present-day counties of Binzhou, Xunyi, Changwu and Chunhua (Zhang, 2004; Li, 2006; Niu 2017; Khayutina, 2020).

“The Archaeological Investigation of the Ancient Bin Area” project has identified and excavated several Proto-Zhou sites in the Jing River Valley, including Nianzipo (Changwu County) (Zhongguo Shehui Kaxue Xueyuan Kaogu Yanjiushuo, 2007), Zaoshugounao (Wang and Chen, 2010; Xibei Daxue Wenwhua Yichan Xueyuan yu Kaoguxue Xueyuan Zhongxin, 2012), Zaolinhetan (Dou et al., 2019) (both in Chunhua County), Xiaweiluo (Xibei Daxue Wenwhua Yichan Xueyuan yu Kaoguxue Xueyuan Zhongxin et al., 2006), Sunjia and Xitou (all three in Xunyi County) (Xibei Daxue Wenhua Yichan xueyuan et al., 2020; Xibei Daxue Wenhua Yichan xueyuan et al., 2021). Taxonomic typological comparison of structures and pottery material, sometimes combined with radiocarbon dating results, has allowed the attribution of these sites to the Proto-Zhou Culture. Sites excavated in the context of this project were among the first in the region at which significant zooarchaeological research was undertaken (Zhongguo Shehui Kaxue Xueyuan Kaogu Yanjiushuo, 2007; Li et al., 2019, 2020) (Figure 1).

The study of faunal assemblages has suggested that the ancient inhabitants of Central Shaanxi herded sheep and goats in the gullies and hills, and raised pigs on the plain and loess platforms, while also practicing some hunting and fishing (Cheng et al., 2017; Festa and Montheith, 2022). Results from the Zaoshugounao and Zaolinhetan assemblages have revealed that residents practiced intensive farming and animal husbandry in and around the settlements, complemented by extensive caprine herding on marginal lands (Li et al., 2019, 2020). By contrast, pigs would appear to have been important domesticated animals at Fengxi (Yuan, 2000), Nianzipo (Zhongguo Shehui Kaxue Xueyuan Kaogu Yanjiushuo, 2007) and Beicun (Cao, 2001), where relatively low ratios of bovids compared to pigs have been identified. Our analysis of the faunal assemblages from Sunjia and Xitou represents novel data on animal economies in the Jing River Valley during the second millennium BCE, which allows for a more solid understanding of the regional subsistence strategies in the context of the emergence of the Zhou authority.

This study is based on the faunal remains excavated from Sunjia in 2017 and Xitou in 2018. Although mostly recovered from residential contexts, a few finds were discovered in four burials in Xitou (M2, M6, M7, and M12). Hand selection was employed during excavation, but no sieving. The animal bone assemblages totaled 1,097 fragments at Sunjia and 519 fragments at Xitou.

The analysis was conducted in two different locations: the zooarchaeology laboratory of Northwest University (Xi’an), and the Northwest University archaeology base in Xunyi County. Taphonomic processes—fragmentation, sub-aerial weathering, burning, gnawing—and human modifications were quantified for all fragments to evaluate the general preservation of the assemblages. The completeness of bones was recorded differently for identified and non-identified bones: the former was measured according to proportion of the whole bone (0.25, 0.25-0-5, 0.5-0.75, ≈1); for the latter maximum length measures were recorded. Sub-aerial weathering and burning were also recorded according to Behrensmeyer (1978) and Stiner et al. (1995), respectively. Worked bones were identified into the lowest identifiable taxonomic unit and classified, according to their possible function considering shape, size and (when possible) use-wear, into four main categories—tools, oracle bones, decorations, and discarded material.

Identification was attempted for every fragment using the reference collection of the zooarchaeological laboratory of Northwest University, online reference resources (e.g., archaeozoo.org) and published identification manuals (e.g., Hillson, 1992; France, 2009). All identified bones were used to calculate the number of identified specimens (NISP) and minimum number of individuals (MNI). NISP was used to quantify species abundance and was calculated using fragments identified to family and beyond following Clason (1972)’s method. By counting fragments that can be cross-mended as one, Clason’s method limits the risk of counting fragments from the same element more than once and, therefore, reduces the boost from large-size bones and animals. Considering the poor preservation of the faunal remains, the limited availability of reference specimens, and the uncertainties surrounding the standards to distinguish sheep and goats (Zeder and Pilaar, 2009; Zeder and Lapham, 2010; Salvagno and Albarella, 2017), the two were combined into the “caprine” category. MNI was calculated on the basis of diagnostic zones present (Dobney and Rielly, 1988). Because of the small number of faunal remains unearthed from graves in Xitou, they were considered along with those from the residential context in the counts of NISP and MNI, in order to provide an omnicomprehensive understanding of the taxonomic abundancy at the site. However, as the inclusion of fauna in funerary contexts implies intentional deposition, the provenance of the bones was signaled in the resulting counts and considered, when necessary, during the interpretation of the results.

Mortality profiles for cattle, pigs and caprines were generated based on bones epiphyseal fusion alongside tooth eruption and wear. Considering the fragmentary evidence, cattle dental aging was attempted using Jones and Sedler (2012), which works relatively well with loose teeth. Caprine mandibles were aged using Payne (1973), which identifies tooth eruption and wear stages for the lower deciduous premolar (dp4), permanent premolar (P4) and molars (M1, M2, and M3). Available dp4 and M3 from single individuals to which age stages could be assigned were also used. The information was then converted into a survivorship curve, which expresses the percentage of animals killed at each age. For pigs, we employed Lemoine et al. (2014)’s “specific system”, which allows to consider both mandibles and maxillae. Epiphyseal fusion analysis for cattle was carried out following O’Connor (2003), while for pigs Zeder et al. (2015) was employed, because it relates to Lemoine et al. (2014)’s dental aging system. Analysis on caprines was conducted by referring to Zeder (2006)’s system, which relates tooth eruption and wear to long bone fusion to refine age determination accuracy.

Measurements were taken for whole elements and undamaged parts following Von den Driesch (1976). Body-size of cattle and pigs was examined using the Log Standard Index (LSI) method. In spite of several imperfections (e.g., the assumption that all bones vary proportionally in size with the standard animal, neglecting other factors impacting the body proportions), the LSI method has the merit of increasing sample sizes, when few measurable specimens are available (Meadow, 1981, Meadow, 1984). Due to the lack of published measurement data from complete Chinese specimen skeletons, Degerbol and Fredskild (1970)’s female aurochs from Mesolithic Denmark, and Russel (1993)’s modern Hungarian female wild boar were used as standard animals for LSI analysis of cattle and pigs, respectively. Pigs’ body size and upper M3 measurements were also used to investigate the domestication status (Mayer, et al., 1998).

This paper has demonstrated that taxonomic abundance and some information about human exploitation of animal resources can be inferred from two small and poorly preserved assemblages. Sunjia and Xitou were rather consistent in terms of taxonomic composition. Both assemblages were dominated by domestic species, though some wild fauna was also present, suggesting that the economy was based on husbandry supplemented with some hunting and fishing. Cattle and caprines dominated the assemblages in Sunjia and Xitou. Our results are consistent with those obtained by Li et al. (2019), and Li et al. (2020) for the coeval neighboring sites of Zaoshugounao and Zaolinhetan (Figure 8; Supplementary Table S3), suggesting a growing importance of these two taxa in the region during the Late Shang period. Increasing bovid herding marks a clear difference in comparison with previous periods, when pigs were predominant. In Central Shaanxi pigs were domesticated relatively early, probably in the Mid-Neolithic (Barton et al., 2009), and their importance grew during the Yangshao and Longshang periods (Hu, 2001; Hu et al., 2011; Wang et al., 2013). A slight, though steady, increase in bovids, at the expense of pigs, has been documented from the end of the Longshan period (Hu, 2001; Hu et al., 2008; Hu et al., 2016), and according to our results, became more dramatic in the late second millennium BCE (for a summary see Festa and Monteith (2022)).

The exploitation strategies present at the sites of Sunjia and Xitou may have been dependent on multiple simultaneous variables. The shift to bovid husbandry could be related to the increasingly cold and dry climate, which followed the Holocene Climatic Optimum, and which could have had an impact on livestock management. While caprines and cattle are fairly tolerant of arid conditions, pigs require a plentiful and dependable supply of water (Burrin, 2001). Also, under cold and arid conditions, agricultural productivity would have declined, prompting a wider and more diversified use of the landscape, including the expansion into marginal lands, which would have been easier with bovid herding (Festa and Monteith, 2022). An et al. (2005) and Huang et al. (2004) have shown that climatic deterioration in the Loess Plateau caused many rain-fed agricultural economies to shift toward agro-pastoralism and mobile pastoralism from the beginning of the second millennium BCE. Similar conclusions were reached by research in Central Asia and Northern China (Frachetti et al., 2017; Wang et al., 2021). Although the residents of the Jing River Valley practiced agriculture and raised some pigs (Lu and Zhang, 2008; Li et al., 2009; Chen et al., 2019), the growing importance of cattle and caprine husbandry may have allowed for a more extensive exploitation of the immediate environment in response to regional climatic changes.

The Proto-Zhou faunal assemblage from the site of Fengxi (Xi’an), located in the plain of the Wei River Valley, includes a relatively larger proportion of pigs than Sunjia and Xitou (Yuan, 2000). Similarly, in Laoniupo (Xi’an), also located in the plain, pig remains were well represented. These two assemblages present certain limitations, one being the sample size of the former, which was very small, including less than 200 elements. Additionally, the assemblage from Fengxi was discovered over the course of 50 years of intermittent archaeological excavations, with recovery and recording protocols not followed to a modern standard: the context in which the bones were and some relevant data are, therefore, controversial. The bones at Laoniupo were mostly found in funerary contexts, which implies intentional selection (Zhang et al., 2007). The variations in the faunal assemblages between these and our sites may, nevertheless, indicate an adaptation to distinct eco-topographic conditions—the former being on a broad flat plain and the latter in a hilly region consisting of gullies and loess platforms. The climatic deterioration following the Climatic Optimum may have affected agriculture to different degrees in the plain and the hilly transitional region to the north, resulting in a different response by the residents of the two areas. Deterioration in climatic conditions would have led to cultivation being less productive in the Jing River valley—where arable land was more limited to begin with—than on the plain. Therefore, while the communities in the plain could rely on a complementary strategy of mixed millet-rice agriculture and pig husbandry (Zhang et al., 2010), the residents of Sunjia and Xitou may have diversified the exploitation of animal resources to cope with new climatic conditions. Bovid husbandry would have been quite efficient, because these animals do not compete with humans for food, do not require copious amounts of water, and could also be used for secondary products.

It is however, noteworthy, that suines, along with deer, were well represented at the sites of Beicun (Yao County) and Nianzipo (Changwu County), which were also located in the hilly region to the north of the Guanzhong Plain. Beicun was reported only in terms of MNI and based on a specific selection of skeletal elements, which not necessarily represent the whole assemblage (Cao, 2001). Additionally, the context in which the skeletal elements were found is controversial and it is unclear whether these bones were from a residential or a funerary context, or both. Similarly, the assemblage from Nianzipo, made up mostly of long bones shafts with traces of human modifications, was retrieved from specific contexts associated with bone production, and may not be fully representative of the whole assemblage (Zhongguo Shehui Kaxue Xueyuan Kaogu Yanjiushuo, 2007). Notwithstanding, the high proportion of pigs at these sites suggests that cultural preferences may have influenced the regional animal exploitation strategies (Figure 8; Supplementary Table S3).

Increasing caprine and cattle herding in Sunjia and Xitou may also have been due to the influence of neighboring pastoral communities in the north. In the second-first millennium BCE mobile and semi-mobile pastoralism dramatically increased, and small and large-scale population movements created a solid network of interaction across Central Asia, Northwest China and Mongolia (Frachetti et al., 2017; Høisæter, 2017). In particular, the growing importance of bovids in the Jing River Valley may be related to the southern migration of pastoralist communities from the Northern Loess Plateau and the Mongolian Plateau. The existence of relations between the residents of Central Shaanxi and those inhabiting the northern regions has been recorded in ancient texts, such as Shiji Zhou Benji (史记·周本纪) (Huang et al., 2003; Khayutina, 2020). Most importantly, such interactions are documented by archaeological evidence of steppe-type of artefacts in several Proto-Zhou sites in Central Shaanxi (Zhang, 2004, Zhang, 2016; Wang and Chen, 2010).

The relatively gradual attrition shown by survivorship curves in Sunjia and Xitou contrasts with a planned and specialized meat production and suggests that the animals were exploited also for their secondary products. However, more data will be required to confirm this supposition. Evidence of worked bones indicates that some taxa were exploited for ritual purposes. For example, cattle scapulae were used to make oracle bones. The Shang used cattle scapulae and turtle shells as divinatory tools (Hou et al., 2018), however at our Proto-Zhou cultural sites only the former was found. Similar finds were recorded at Zaoshugounao and Zaolinhetan (Li et al., 2020), signaling some difference between the Shang and the Proto-Zhou in terms of ritual practices. The percentage of oracle bones in Sunjia (0.4% of the fragments) and Xitou (1.5% of the fragments) was comparable to coeval sites at Zaoshugounao (0.5% NISP) and Zaolinhetan (1.5% NISP) (Li et al., 2020), but lower than at Nianzipo (Changwu County) (3% NISP), where specimens made of horse and other animals’ scapulae were also found (Zhongguo Shehui Kaxue Xueyuan Kaogu Yanjiushuo, 2007). This may indicate a certain degree of ritual variability in the region, and, at the same time, reflect a decline of Shang practices in some areas of the Jing River Valley, in favor of other divinatory systems, such as that by hexagrams, mentioned in written sources (Khayutina, 2020). Only one fragmented oracle bone was found in the filling of grave M7 in Xitou. This was the only cattle remain recovered from our mortuary contexts, suggesting the development of different ritual practices compared to the Shang period, when whole or dismembered cattle were placed in graves (Lu, 2015; Hou et al., 2019). This inference is not only based on faunal assemblages from the four graves examined in this study, but also on comparable finds at Zaoshuguonao (Li et al., 2020). By contrast, the discovery of three bones belonging to (likely) one young dog in grave M2 in Xitou seems to finds parallels with dog mortuary depositions of the Shang (Li and Campbell, 2019), further supporting the variety of ritual traditions present in the Jing River Valley in the late 11th century BCE.

Despite the close proximity (∼4 km) and the shared topography and climate, a significant variation in cattle body size was observed between Sunjia and Xitou. In spite of the small assemblage and the above-mentioned limitations concerning the bones selection, this distinction is quite remarkable and it is worthy to be discussed in terms of extensive/intensive subsistence practices. As discussed above, in the late second millennium BCE, new economic strategies developed in the Jing River valley as a response to climatic changes, which brough about a certain degree of reorganization of the rural landscape and promoted the exploitation of more marginal lands. Archaeobotanical data for Xitou and Sunjia are currently not available, however, crop cultivation and consumption in the region has been demonstrated by archaeobotanical and isotope research results from neighboring Proto-Zhou sites (Lan 2017; Chen et al., 2019), and various degrees of reliance on agriculture have been discussed by Li et al. (2020) for the Zaoshuguonao and Zaolinhetan sites. If this was the case, foddering and breeding strategies would have been adjusted to different farming systems, affecting the animal size (Trentacoste, 2020). Different degrees of engagement in agricultural practice would have had a significant impact on localized animal exploitation, in particular, the use of cattle. A more intense and extensive agricultural activity would have favored animal labour in the fields, and, therefore, the investment in large specimens, potentially even oxen, for traction, which would have significantly increased land productivity; by contrast, small-scale agricultural systems would have incentivized human labor, and, therefore, the exploitation of smaller and cheaper cows for secondary products and light work (Bogaard et al., 2019; Trentacoste et al., 2021). The use of cattle for traction in Northern China during the late Shang period has been demonstrated by paleopathological studies on animal bones (Lin et al., 2018), however, the poor conditions of our assemblages hampered such analysis. In the absence of this data, it might be possible to use the size difference in cattle to differentiate between economic structures (Trentacoste, et al., 2021): a larger, more complex agricultural center, such as Xitou, would have required sizable animals, while in smaller settlements, such as Sunjia, smaller less-demanding female specimens, would have beeen preferred.

A non-statistically significant, yet notable, variation in pig size was identified between the sites of Sunjia and Xitou, with the former generally presenting smaller specimens than the latter. Although the sample size used in this study was small, this variation can signal different animal husbandry practices at the two sites. Chen et al. (2014)’s isotopic analyses of pig bones from the Mid-Late Neolithic sites of Dongying and Wayaogou, in the Wei River valley, have shown various feeding strategies in the region, with some pigs kept on intensive foddering, whereas others received less millet fodder. If the occupants of Sunjia and Xitou engaged in agriculture to different degrees, this may have had an impact on pig husbandry strategies, as less productivity would have left less surplus for pigs. Different feeding strategies would, in turn, have influenced the animals’ size.

The argument that the residents of the two sites may have relied on different agricultural and livestock management strategies is further suggested by the higher caprine/pig ratio by NISP in Sunjia (1.9), compared to that in Xitou (1.3), which would indicate a lower degree of agricultural engagement in the former site (Miller 1997). Considering that the two sites are only about 4 km apart and share environmental and climatic conditions, different economic strategies could have epended, at least partially, on social, cultural and political factors.

Wild animals were scarce, particularly in Xitou, where the dearth of arrowheads from the archaeological context further suggests limited hunting (Xibei Daxue Wenhua Yichan xueyuan et al., 2020). A few shell fragments constitute the only evidence of aquatic resource exploitation. This is unexpected given the large regional water system and the fair use of mollusks and fish documented from various sites in Central Shaanxi, both earlier than, and contemporary to, Sunjia and Xitou (Cheng et al., 2017; Li et al., 2020). This lack in our assemblages is presumably due to poor sieving and taphonomic agents. The relative paucity of wild taxa in our sites is in line with regional zooarchaeological and paleodietary research, which has shown that while hunting and fishing were practiced in the Neolithic, their importance declined during the Longshan period, possibly due to population growth and the increasing demand for meat, both for consumption and ritual purposes (Cheng et al., 2017). The decrease continued during the Late Shang period, when hunting and fishing may have become less related to the need for food (Li et al., 2021; Festa and Monteith, 2022) (Figure 9; Supplementary Table S3). Ancient texts and archaeological evidence indicate that hunting, in particular, was a significant social activity during the Shang and Zhou dynastic periods (Cheng et al., 2017; Fiskesjö, 2001). Most importantly, faunal evidence from Sunjia and Xitou indicates that wild taxa, especially deer, were exploited for tool-making, supporting Li et al. (2021)’s argument of a shift occurred in the cervids regional exploitation, from meat to antlers. The discovery of some unworked post-cranial elements from deer associated with tools made of antlers—and to a lesser extent, bones and teeth—and debris suggests that local residents hunted cervids and produced artefacts locally.

Although the faunal remains from Sunjia and Xitou were sub-optimally preserved, their analysis is an important addition to zooarchaeological research as it represents a novel interrogation of micro-regional variation in the exploitation of animal resources in the Jing River valley in the Proto-Zhou period. A growing importance of bovids was identified at the sites. A diversified use of animal resources may have been prompted by the local population’s need to exploit the immediate and peripheral environment more efficiently, in response to the climatic deterioration following the Climatic Optimum. Interactions with northern communities of pastoralists, which migrated southward from the northern Loess Plateau and the Mongolian Plateau, could also have promoted more intensive bovid husbandry in the region.

A diversified use of animal resources and a wider and more efficient exploitation of the immediate environment, in addition to the alliances with neighboring communities, may have underpinned the socio-economic foundation behind the emergence of the Zhou as a political power. Li et al. (2020) speculate that diverse faunal use could reflect the development of economic and social complexity in the Jing River Valley in the late second millennium BCE. Such a conclusion was supported by our research results. Patterns of livestock biometry and relative taxonomic abundance in Sunjia and Xitou indicate that the residents of the two sites may have engaged in agriculture to different degrees and relied on different livestock management strategies. Xitou would have been a larger agricultural center, while Sunjia would have been a smaller settlement. This distinction suggests the development of some degree of regional social complexity in the Jing River Valley in the late second millennium BCE. While this study has demonstrated that variations in faunal exploitation strategies can inform socio-economic developments, these should be the subjects for further investigation, when more zooarchaeological results will be considered along with relevant archaeological evidence.