Fourth millennium BP human–animal dynamics in the SETP

Faunal research into human–animal dynamics and early food production in the STP is still in its infancy. New faunal data from the Klu lding site illustrate that among the specimens classified into the subfamily Caprinae, two could be identified as domestic sheep (O. aries). Conversely, the presence of wild Caprinae could not be confirmed in the assemblage studied (Table 2). Despite limitations of sample size, positive identification of the domestic form and lack of unequivocal evidence for wild Caprinae suggest that domestic sheep likely figured prominently in the non-identified Caprinae assemblage as well (n = 15; i.e., 19.7% of NISP). Thus, on the assumption that all taxa identified to the species level contributed significantly to the non-identified assemblage, it seems reasonable to postulate that sheep husbandry was essential in the livestock economy of Klu lding.

The relative abundance of pig remains (10.5–14.4%) indicates that swine husbandry contributed to human subsistence as well, possibly equivalent to sheep. The only Bos specimen identified by us suggests that large bovines, be it domestic cattle, yak, or their hybrid (termed “dzo”), were present in small numbers as well. For reasons of economic efficiency, however, the keeping of large ruminants often goes hand in hand with their use as draught, dairy, or pack animals, but unequivocal evidence for this is lacking. Nevertheless, the economic importance of domestic bovines may be underestimated in view of the pronounced fragmentation of the bone material at Klu lding.

During excavation of Klu lding, a square-corner stone enclosure (Q1) made of large gravels was partially uncovered in layer ③ of T1, with a length of 450 cm exposed inside the trench. The radiocarbon date of layer ② (Table 1) suggests its construction before 3400 cal yr BP. Similar stone enclosures were found in numbers at Bangga in the south-central TP, with early-phase structures dating to 3000–2800 cal yr BP (Lu et al., Reference Lu, Chen, Zhang, Tang, Lemoine, Wangdue, Chen, Liu and Frachetti2021). In comparison to the findings from stone enclosures F2/F5 at Bangga yielding abundant animal dung and interpreted by Lu et al. (Reference Lu, Chen, Zhang, Tang, Lemoine, Wangdue, Chen, Liu and Frachetti2021, see Fig. 3 in this reference) as animal corrals, the possibility of Q1 at Klu lding serving the same purpose cannot be excluded. However, stone structures are prevalent in the prehistoric and historic TP, so without additional evidence, any statement regarding their exact function remains speculative.

Figure 3. Proposed pathways of cultural exchange in Middle–Late Holocene, distribution of prehistoric culture groups in central and East Asia, archaeological sites mentioned in the text, location where palaeoclimatic records were obtained. 1: Mehrgarh; 2: Harappa; 3: Burzahom; 4: Gepa Serual; 5: Mebrak/Phudzeling; 6: Zhongba; 7: Nizhnaya; 8: Kyamo; 9: Khog Gzung; 10: Khuurai Gobi2; 11: Qugong; 12: Yagshiin Huduu2; 13: Bangga; 14: Klu lding; 15: Kha lding; 16: Xiaoenda; 17: Karuo; 18: Shatar Chuluu1; 19: Yingpanshan; 20: Ashaonao; 21: Sanxingdui; 22: Dadiwan; 23: Shimao; 24: Taosi; 25: Shihushan; 26: Erlitou; 27: Youyao; 28: Jiahu; 29: Cishan; 30: Kuahuqiao; 31: Houtaomuga. Hexagons for palaeoclimate records: I: Bangong Co; II: Aweng Co; III: Ngamring Tso; IV: Paru Co; V: Delingha; VI: Tiancai Lake; VII: Heihai Lake. The red box indicates the area of the studied archaeological sites.

Apart from domestic livestock, a diverse archaeofauna comprising remains of Sichuan vole, a small cat, a fox, a leopard, musk deer, barking deer, birds, and fishes was recovered at Klu lding. These taxa formed part of the local fauna populating the natural environment surrounding the site. As such, the vole and small cat most likely represent commensal species frequenting human habitats in search of food. With the onset of sedentism and cereal cultivation in SW Asia at the transition of the Pleistocene to the Holocene, the human niche witnessed increasing numbers of seed-eating rodents (Tchernov, Reference Tchernov1984; Willcox and Stordeur, Reference Willcox and Stordeur2012). Higher rodent densities certainly attracted the species’ natural enemies, such as (wild) cats (Vigne et al., Reference Vigne, Guilaine, Debue, Haye and Gérard2004, Reference Vigne, Briois, Zazzo, Willcox, Cucchi, Thiébault and Carrère2012) and foxes (Peters et al., Reference Peters, Arbuckle, Pöllath, Özdoğan, Başgelen, Kuniholm and Galatasaray2014), and the fact that crop seeds including millet have been found in numbers in the archaeobotanical samples of Klu lding (Wang, Y., personal communication, August 2021) makes commensalism a likely explanation. Elsewhere in China, the presence of commensal carnivores as a means of reducing crop losses has already been postulated for Neolithic farming villages of the Yangshao culture dating to the sixth millennium BP (Guan et al., Reference Guan, Hu, Hu, Sun and Wang2008; Hu et al., Reference Hu, Hu, Wang, Wu, Marshall, Chen, Hou and Wang2014; Vigne et al., Reference Vigne, Evin, Cucchi, Dai, Yu, Hu and Soulages2016). Just as in the ancient Near East (e.g., Weissbrod, Reference Weissbrod and Dean2010), the relative abundance of cereal finds and the presence of rodents and their predators testify to the sedentary agricultural nature of the Klu lding settlement.

With regard to the other vertebrate taxa, hunting or trapping of pika, leopard, musk deer, barking deer, birds, and freshwater fishes primarily served food purposes. Similar faunal spectra have been reported from other SETP sites (Huang and Leng, Reference Huang and Leng1985; Li, Reference Li2007; Zhang et al., Reference Zhang, Chen, Marshall, Lü, Lemoine, Wangyal, Dorje and Liu2019b). Besides meat and fat, the furs of pikas, foxes, and leopards were certainly valued for clothing (Feng et al., Reference Feng, Cai and Zheng1986; Monchot and Gendron, Reference Monchot and Gendron2011), while the hides of deer and Caprinae may have been used as seat carpets. (Feng et al., Reference Feng, Cai and Zheng1986). Deer musk obtained from the species’ caudal glands may have been appreciated for fragrance or as admixture to medicine, among other uses (e.g., Green, Reference Green1986; Yang et al., Reference Yang, Meng, Xia and Feng2003). As wild taxa account for almost 28% of the assemblage identified, hunting, fowling, and fishing still represented essential subsistence activities at Klu lding, even if the relative importance of these wild taxa had already decreased compared with the earlier settlement sites of Xiaoenda and Karuo (Li, Reference Li2007; Zhang et al., Reference Zhang, Chen, Marshall, Lü, Lemoine, Wangyal, Dorje and Liu2019b).

In summary, the fauna from Klu lding illustrates the dynamics of human–animal–environment dynamics in the SETP during the mid-fourth millennium BP. In this warm-humid and most suitable area for human habitation in Tibet, the site inhabitants explored a diverse range of food resources. Their subsistence combined husbandry of pigs, sheep, and cattle with millet agriculture, the latter also attracting crop-eating rodents and their enemies, more precisely wild small felids. Meanwhile, a large part of the resources were obtained through the hunting of leopards, foxes, different species of deer, and pikas, as well as fowling and fishing.

Spread of millet–pig agriculture in the STP

Pig domestication and early husbandry can be evidenced in the Central Plain of northern China (i.e., Jiahu site, Jiahu culture) and the Lower Yangtze of southern China (i.e., Kuahuqiao site, Kuahuqiao culture) some 9000–8000 years ago (Luo and Zhang, Reference Luo and Zhang2008; Cucchi et al., Reference Cucchi, Hulme-Beaman, Yuan and Dobney2011). Millet was domesticated in northern China ca. 10,000 ago (Cishan site, Cishan culture), and by the sixth millennium BP, millet agriculture had already dispersed across much of northern China (Lu et al., Reference Lu, Zhang, Liu, Wu, Li, Zhou and Ye2009; Yang et al., Reference Yang, Wan, Perry, Lu, Wang, Zhao and Li2012; Zhao, Reference Zhao2014). As such, millet–pig farming developed into the main mode of subsistence of the Yangshao (7–5 ka) and Majiayao (5.3–4 ka) farming communities inhabiting the Yellow River basin (Yuan, Reference Yuan1999; Wang et al., Reference Wang, Martin, Hu and Wang2012, Reference Wang, Martin, Wang and Hu2015). Millet–pig farming has also been observed in Dadiwan, situated at 1593 m asl (6.5–4.9 ka; Barton et al, Reference Barton, Newsome, Chen, Wang, Guilderson and Bettinger2009) close to the NETP, and along the upper Min River at the eastern margin of the TP in NW Sichuan province, as exemplified at the Yingpanshan site (5.3–4.6 ka; 1650 m asl; Zhao and Chen, Reference Zhao and Chen2011; He, Reference He2015).

In view of the geographic origins of pig husbandry in China, domestic pigs were introduced to the TP from the east, along with millet cultivation. Of interest is the fact that in the STP, Sus remains have been identified in sites located above 3000 m asl, for instance at 3700 m asl Qugong (3.8–3 ka, Qugong culture; Zhou, Reference Zhou1999) or at the earlier sites of Xiaoenda (3140 m asl; Zhang et al., Reference Zhang, Chen, Marshall, Lü, Lemoine, Wangyal, Dorje and Liu2019b), Karuo (3100 m asl; Huang and Leng, Reference Huang and Leng1985), though in quite low numbers. Debate continues regarding whether these Sus remains represent domestic pigs or wild boars (Zhou, Reference Zhou1999; Li, Reference Li2007; Zhang et al., Reference Zhang, Chen, Marshall, Lü, Lemoine, Wangyal, Dorje and Liu2019b). Conceivably, the species’ successful association with millet-cultivating Neolithic communities inhabiting the Central Plain (Han, Reference Han2012) allows arguing in favour of domestic pigs spreading along with millet farming Yangshao and Majiayao communities that migrated into the TP from lowland eastern China. As the aforementioned Tibetan sites are all close to or above the altitude limit of the natural distribution usually accepted for Eurasian wild boar (~3000 m asl; Feng et al., Reference Feng, Cai and Zheng1986; Groves and Grubb, Reference Groves, Grubb and Oliver1993; Wilson and Reeder, Reference Wilson and Reeder1993; Keuling and Leus, Reference Keuling and Leus2019), the arrival of pig husbandry offers the most plausible explanation for the species’ presence in the fifth millennium BP contexts of the study region.

Although the site inhabitants obviously managed to provide suitable fodder and indoor space so that pigs could endure the harsh Tibetan winter, numbers may have been limited by the area of available space and the amounts of food the community could spare (e.g., Mitchell, Reference Mitchell2002; Albarella et al., Reference Albarella, Dobney, Ervynck and Rowley-Conwy2007). Investigation of the correlation between the intensity of millet farming and the rather low frequency of Sus in archaeological contexts of the TP needs further exploration, particularly when the climate turned colder in the Middle–Late Holocene TP and millet cultivation was at low-level production due to ecological constraints (d'Alpoim Guedes, Reference d'Alpoim Guedes2015). Besides millet, other cereals, including barley, naked barley, wheat, and Tartary buckwheat identified in STEP sites served as food for humans and perhaps animals as well (Gao et al., Reference Gao, Yang, Ma, Tong and Yang2021; Song et al., Reference Song, Gao, Tang, Zhang, Tang, Xu and Wangyal2021). With more reliable numbers at hand, a closer look at the demographic profiles of pigs could be helpful to test the hypothesis that people removed surplus young and old animals from the herd to save fodder for valuable breeding stock over the winter. Finally, thriving well in a temperate habitat, domestic lineages had to adapt to the conditions of living at significantly higher altitudes. Future ancient DNA studies will have to clarify whether this involved deliberate selection by pig breeders or even hybridization with local wild boar.

Origins of bovid pastoralism in the STP

At present, none of the sites located in the STP and predating 4 ka yielded unequivocal evidence for human exploitation of domestic bovids. This assumption draws upon the faunal records from Xiaoenda (Zhang et al., Reference Zhang, Chen, Marshall, Lü, Lemoine, Wangyal, Dorje and Liu2019b; this study), Karuo (Huang and Leng, Reference Huang and Leng1985; Li, Reference Li2007), and Mabu Co (located at the very southern edge of the TP; fauna analysed by the first author and colleagues), although in the course of the fifth millennium BP, SETP witnessed the introduction of agricultural practices including millet cultivation and pig husbandry, as discussed earlier.

Relative to the first half of the fourth millennium BP, earlier work proposed that the inhabitants of Qugong in the central TP kept domestic sheep and yak (Zhou, Reference Zhou1999). Though livestock husbandry at ~3700 cal yr BP cannot be excluded, taxonomic identification of the specimens and their ¹⁴C dating need verification. Recent archaeobotanical work at Qugong by Gao et al. (Reference Gao, Yang, Ma, Tong and Yang2021) pointed out issues with ¹⁴C dating of contexts likely due to the old wood effect and/or the use of lab instrumentation generating dates with wide analytical errors (Schiffer, Reference Schiffer1986; Dong et al., Reference Dong, Wang and Ren2014). In addition, the Ovis skull found in Pit 5 has been classified taxonomically as a domestic sheep of the “Tibetan breed” due to its large horns and very large size (Zhou, Reference Zhou1999, p. 238). However, given the widespread occurrence of argali in the region, criteria separating O. ammon from domestic “Tibetan sheep” must be detailed. By analogy, morphological separation of domestic yak from its wild relative and from cattle × yak hybrids is essential to postulate the early presence of the first.

After 3.5 ka, domestic sheep and cattle/yak gain visibility in the archaeological record of the STP, with remains now being identified in every site located above 3000 m asl (Supplementary Material D). Current evidence thus suggests that bovid husbandry gained a foothold around the middle of the fourth millennium BP. Following initial introduction of the domestic bovids, STP witnessed the establishment of an agro-pastoral system combining wheat and barley cultivation with livestock husbandry (Gao et al., Reference Gao, Yang, Ma, Tong and Yang2021). From the early third millennium BP onward, however, barley becomes the dominant crop staple at the expense of millet in pastoral communities inhabiting high-elevations in the NETP (Qinghai) and central STP (d'Alpoim Guedes et al., Reference d'Alpoim Guedes, Manning and Bocinsky2016; Tang et al., Reference Tang, Lu, Spengler, Boivin, Song, Wangdue, Chen, Liu and Zhang2021). Interestingly, this shift in cereal exploitation seems restricted to those regions where mobile pastoralism became an essential feature of local economies.

Like elsewhere in alpine Eurasia, the adoption and widespread use of livestock in the STP relates to the species’ adaptation to high-altitude environments and pasture opportunities (Schaller, Reference Schaller1977; Felius, Reference Felius1985; IUCN/SSC, 1997) on the one hand, and their returns in terms of lifetime (secondary) products, such as milk, hair/wool, dung, and labor on the other (Greenfield, Reference Greenfield2010). Perhaps noteworthy as well is the fact that in mountainous terrain, small ruminants also can be used for transporting goods—for instance, bags containing salt (Yang and Zheng, Reference Yang and Zheng2001). Moreover, caprines and cattle/yak can be pastured in the valleys during wintertime to avoid harsh alpine conditions and periods of food shortage, but will return to higher altitudes to enjoy summer pastures without too much need of human attention for feeding and shelter (Cai, Reference Cai1981; Ryder, Reference Ryder1983). Conceivably, lowland lineages of sheep and cattle translocated into the Himalayas at altitudes well above 3000 m asl needed specific adaptations in order to thrive well under such conditions (Zhang et al., Reference Zhang, Dong, Wang, Ren, Qiang and Chen2016; Wang, Reference Wang2017; Wang et al., Reference Wang, Ju, Jiang, Zhong, Liu, Wang and Hoff2021a). Deliberate selection by breeders seems one option, but with respect to sheep and cattle, hybridization respectively with local wild argali (Ovis ammon) (Aniwashi et al., Reference Aniwashi, Ali Kaleri, Sulaiman, Li and Zhuang2011; Wang, Reference Wang2017) and yak (Bos mutus) (Liu et al., Reference Liu, Li, Yan, Li, Wu, Pei, Yan, Yang, Guo and Lan2020; Wang et al., Reference Wang, Ju, Jiang, Zhong, Liu, Wang and Hoff2021a) could have accelerated acquisition of vital adaptive and in the meantime genetically fixed traits to deal with conditions of hypoxia and ultraviolet signaling. As these traits have been identified in the chromosomal DNA of modern representatives of Tibetan sheep (Hu et al., Reference Hu, Yang, Xie, Lv, Cao, Li and Liu2019) and cattle (Chen et al., Reference Chen, Cai, Chen, Li, Wang, Huang and Hu2018; Wu et al., Reference Wu, Ding, Wang, Wójcik, Zhang, Tokarska and Li2018b), it raises the question whether hybridization of domestic lineages with local wild forms had a much deeper history. Estimates using the molecular clock offer a timeframe of 2400–1400 years ago for introgression events between cattle and yak (Chen et al., Reference Chen, Cai, Chen, Li, Wang, Huang and Hu2018). That said, analysis of the genetic makeup of prehistoric sheep and cattle is essential to refine the picture.

If, as already said, the northern Fertile Crescent witnessed the domestication of wild sheep, goat, and cattle based on zooarchaeological (Peters et al., Reference Peters, Helmer, Driesch and Saña Segui1999, Reference Peters, Dreisch, Helmer, Vigne, Peters and Helmer2005, Reference Peters, Arbuckle, Pöllath, Özdoğan, Başgelen, Kuniholm and Galatasaray2014; Zeder and Hesse, Reference Zeder and Hesse2000; Helmer et al., Reference Helmer, Gourichon, Monchot, Peters, Sana, Vigne, Peters and Helmer2005) and ancient DNA studies (Meadows et al., Reference Meadows, Hiendleder and Kijas2011; Bollongino et al., Reference Bollongino, Burger, Powell, Mashkour, Vigne and Thomas2012; Demirci, Reference Demirci2012, Reference Demirci, Baştanlar, Dağtaş, Pişkin, Engin, Özer, Yüncü, Doğan and Togan2013; Lv et al., Reference Lv, Peng, Yang, Zhao, Li, Liu, Ma, Zhao, Yang, Wang and Li2015; Scheu et al., Reference Scheu, Powell, Bollongino, Vigne, Tresset, Çakırlar, Benecke and Burger2015), the routes by which these domestic ungulates spread across central, South, and East Asia can only be addressed in broad outline for reasons of poor archaeological coverage in many parts of this vast region. Migratory routes of sheep pastoralism across Europe and Asia have been proposed based on the study of endogenous retroviruses (Chessa et al., Reference Chessa, Pereira, Arnaud, Amorim, Goyache, Mainland and Kao2009) and mitogenomes (Lv et al., Reference Lv, Peng, Yang, Zhao, Li, Liu, Ma, Zhao, Yang, Wang and Li2015) of modern Eurasian sheep breeds and wild Ovis. The Mongolian Plateau region was postulated as acting as a main “transportation hub” that witnessed two major migratory waves by the fifth millennium BP (Lv et al., Reference Lv, Peng, Yang, Zhao, Li, Liu, Ma, Zhao, Yang, Wang and Li2015). According to direct radiocarbon dating and proteomics analysis, sheep were exploited by Afanasievo communities of the Altai Mountains and Mongolian Plateau ca. 5300–4800 cal yr BP (Hermes et al., Reference Hermes, Frachetti, Doumani Dupuy, Mar'yashev, Nebel and Makarewicz2019; Wilkin et al., Reference Wilkin, Miller, Taylor, Miller, Hagan, Bleasdale and Scott2020). In NE China, direct radiocarbon dating and aDNA analyses confirmed that cattle (Bos taurus) of Near Eastern origin was exploited at Jilin by ca. 5300 cal yr BP (Cai et al., Reference Cai, Zhang, Zhu, Chen, Wang, Zhao, Ma, Royle, Zhou and Yang2018b). Furthermore, domestic sheep were exploited in the upper and middle Yellow River basin (including Qinghai, Gansu, southern Shaanxi, and Shanxi) by the late fifth/early fourth millennium BP (IACASS and SPLCRB, 2005; Yan and He, Reference Yan and He2005; Cai et al., Reference Cai, Tang, Yu, Han, Ren, Zhao, Zhu and Zhou2011; Li, Reference Li2012; Wang, Reference Wang2017; Brunson et al., Reference Brunson, Lele, Xin, Xiaoling, Hui, Jing and Flad2020), while at sites located at higher latitudes in northern Shaanxi and Shanxi, the species may have been present a few centuries earlier (Dodson et al., Reference Dodson, Dodson, Banati, Li, Atahan, Hu, Middleton, Zhou and Nan2014; Hu et al., Reference Hu, Yang, Sun and Shao2016, Reference Hu, Yang, Yang, Shao and Di2022; Yang et al., Reference Yang, Hu, Guo and Wang2017; Sun et al., Reference Sun, Shao and Di2020; Hu, Reference Hu2021b). Zooarchaeological and ancient DNA analyses moreover confirm that cattle appeared in the middle Yellow River Valley at broadly the same time ca. 4.5–4 ka (Cai et al., Reference Cai, Sun, Tang, Hu, Li, Zhao, Xiang and Zhou2014, Reference Cai, Zhang, Shao, Sun, Zhu and Yang2018a; Yu, Reference Yu2020), suggesting that their spatiotemporal dispersal may have coincided with that of domestic sheep, possibly even along the same route(s) of dispersal. In the same region, goats likely occurred a few centuries later than sheep.

Thus, by 5.5–5 ka, sheep and cattle were raised by Neolithic communities inhabiting the Mongolian Plateau and NE China. From there, livestock husbandry progressed south into the northern Shanxi and Shaanxi Provinces at around 4.5 ka and further into the Yellow River basin to reach the NETP around 4 ka. In this respect, the spatiotemporal pattern proposed for the onset of livestock farming in NE China and Gansu/Qinghai seems paralleled by routes of dispersal and timing of arrival of wheat and barley (Dodson et al., Reference Dodson, Li, Zhou, Zhao, Sun and Atahan2013; Chen et al., Reference Chen, Dong, Zhang, Liu, Jia, An, Ma and Xie2015a; Stevens et al., Reference Stevens, Murphy, Roberts, Lucas, Silva and Fuller2016; Liu et al., Reference Liu, Lister, Zhao, Petrie, Zeng, Jones and Staff2017). By the same route but in the opposite direction, broomcorn millet spread into central Asia, with evidence for its cultivation 4.2 ka in Begash, south Kazakhstan (Stevens et al., Reference Stevens, Murphy, Roberts, Lucas, Silva and Fuller2016).

Current opinion agrees that in China, livestock husbandry dispersed south from the Yellow River basin. To reach the SWTP, the most likely route taken (>1500 km) crossed the Tao River basin in Gansu to continue through the mountain and gorge regions of northwest Sichuan and across the Hengduan Mountains. Being adapted to cold-temperate environmental conditions prevailing in NE China, dispersal must have been challenging for livestock populations, because herds faced new climate and vegetation conditions when crossing distinct eco-geographic zones. Nevertheless, the recent evidence from early occupations in Ashaonao, Jiuzhaigou, may exemplify such north-south dispersal during the fourth millennium BP (d'Alpoim Guedes et al., Reference d'Alpoim Guedes, Lu, Hein and Han2017; Lv et al., Reference Lv, Fan, Yang and Li2017; Zhang et al., Reference Zhang, Li, Ma and Lv2017b).

As shown for the SW Asian domestic crops wheat and barley, there might be different routes and episodes for domestic bovids spreading into China in prehistory. At present, four routes into China have been proposed for the spread of wheat and barley, including the Eurasian steppe route, the sea route, the Silk Road, and possibly the South Asia route (Zhao, Reference Zhao2009; Flad et al., Reference Flad, Li, Wu and Zhao2010; Barton and An, Reference Barton and An2014; Betts et al., Reference Betts, Jia and Dodson2014; Liu et al., Reference Liu, Lister, Zhao, Petrie, Zeng, Jones and Staff2017; Lister et al., Reference Lister, Jones, Oliveira, Petrie, Liu, Cockram, Kneale, Kovaleva and Jones2018; Long et al., Reference Long, Leipe, Jin, Wagner, Guo, Schröder and Tarasov2018). The wheat–barley–pea combination and the round-bottomed pottery basins discovered at Qugong (~3.5 ka) in the central STP (Tang, Reference Tang2014; Gao et al., Reference Gao, Yang, Ma, Tong and Yang2021), and the cowrie shells from Karuo (Tang, Reference Tang2014) in the SETP were most likely from northern South Asia, and the archaeobotanical assemblage including barley, pea, millet, and rice found in Mebrak/Phudzeling (3–2.1 ka) in Nepal illustrates an important trade route connecting the Indian subcontinent with the TP (Knörzer, Reference Knörzer2000). Given that domestic sheep and goats appeared in the NW Indian subcontinent comparably early, that is, at Neolithic Mehrgarh (8.3–6 ka), and with caprine husbandry spreading across much of South Asia in the subsequent millennia (Meadow, Reference Meadow, Crabtree, Ryan and Campana1989, Reference Meadow, Clutton-Brock J. and S1993, Reference Meadow and Harris1996; Thomas, Reference Thomas2002; Miller, Reference Miller2004; Joglekar et al., Reference Joglekar, Sharada and Abhayan2013; Chase, Reference Chase2014), the possibility of a southern, sub-Himalayan route of introduction into Tibet must be considered. Evidence for cultural exchange between NW South Asia, Kashmir, and the STP since the late fifth millennium BP (Mughal and Halim, Reference Mughal and Halim1972; Huo, Reference Huo1990; Han, Reference Han2012; Cao et al., Reference Cao, Wen, Yu, Shargan, Tash and Wang2021) underscores the possibility of a livestock transfer. According to this scenario, sheep and goats may have travelled along the hilly flanks from the sites at the foothills in NW subcontinent, through Kashmir, and then along the Sengge Zangbo River valley into the SWTP. Alternatively, they could have followed the mountain ranges along the Sutlej River valley from the Indus plain into the CSTP. Considering the nearly synchronous presence of sheep in the SWTP (represented by Gepa Serual), CSTP (represented by Qugong), and SETP (represented by Klu lding), several trajectories of introduction into the Himalayas seem to be a scenario worth considering, even if definitive proof of this still needs to be provided. The genetic contributions of Pamir O. ammon to Tibetan domestic sheep (Hu et al., Reference Hu, Yang, Xie, Lv, Cao, Li and Liu2019) and of South Asian zebu cattle (Bos indicus) (Chen et al., Reference Chen, Lin, Baig, Mitra, Lopes, Santos and Magee2010) in ancient central plain Chinese cattle (Cai et al., Reference Cai, Sun, Tang, Hu, Li, Zhao, Xiang and Zhou2014) equally suggest the possible existence of a “southern route” of livestock translocation. It agrees with previous archaeological studies suggesting that the formation of a “highland silk road” has deep prehistoric roots (Huo, Reference Huo2017). Hence, regardless of its formidable altitude and varying climates, the STP was likely a dynamic arena of cultural activity spanning distant regions of central Asia, South Asia, and East Asia as early as 5 ka (Tang, Reference Tang2014; d'Alpoim Guedes, Reference d'Alpoim Guedes2015; Huo, Reference Huo2017; Liu et al., Reference Liu, Jones, Matuzeviciute, Hunt, Lister, An, Przelomska, Kneale, Zhao and Jones2019a; Gao et al., Reference Gao, Yang, Ma, Tong and Yang2021).

On the other hand, there are also arguments against a sub-Himalayan route of dispersal (Witzel, Reference Witzel and Osada2009; Stevens et al., Reference Stevens, Murphy, Roberts, Lucas, Silva and Fuller2016). To test the hypothesis of a transfer of domestic bovids via a sub-Himalayan corridor, additional excavations and zooarchaeological studies involving ancient DNA analysis examining phylogenetic relationships with either northern Eurasian or southern Asian livestock lineages is needed for STP archaeological sites along potential trajectories.

Three-phase subsistence development and formation of Tibetan pastoralism

The TP hosts one of the world's largest pastoral systems, the formation of which is still poorly understood (Miehe et al., Reference Miehe, Miehe, Kaiser, Reudenbach, Behrendes, Duo and Schlütz2009; Wei et al., Reference Wei, Hou, Fan, Madsen, Qin, Du, Sun, Gao and Shan2020; Huang et al., Reference Huang, Zhang, Storozum, Liu, Gill, Xiang and Ren2020). Against the background of Holocene climate archives in the wider region and by contrasting this information with zooarchaeological and archaeobotanical findings, this study evaluated and integrated ecological and biocultural developments in the study area in order to trace the dynamics of the human–animal–environment relationship and the emergence of pastoralism on the TP.

Precipitation and temperature records have been obtained in different regions of the TP (see yellow hexagons in Fig. 3). Most Holocene archives illustrate that towards the end of the Holocene thermal maximum, the climate became cooler and drier (Fig. 4a–d). Figure 4b and d show the decline in precipitation in the SWTP (Fig. 3, hexagon I) and CSTP (Fig. 3, hexagon III) respectively. The hydrogen data from Delingha in the NETP (Fig. 3, hexagon V; Yang et al., Reference Yang, Qin, Bräuning, Osborn, Trouet, Ljungqvist and Esper2021) and the temperature data from Lakes Tiancai and Heihai in the SETP (Fig. 3, hexagons VI and VII; Chang et al., Reference Chang, Zhang, Liu and Shulmeister2017; Zhang et al., Reference Zhang, Chang, Cao, Sun, Shulmeister, Tang, Langdon, Yang and Shen2017a) show similar patterns. Two other climate archives seem to diverge, though, namely the ones from Paru Co in the STP (Fig. 3, hexagon IV; Bird et al., Reference Bird, Polisar, Lei, Thompson, Yao, Finney, Bain, Pompeani and Steinman2014) and Aweng Co in the SETP (Fig. 3, hexagon II; Li et al., Reference Li, Wang, Zhang, Lei and Hou2017), most likely for reasons of low resolution of the data and the effects of complex factors other than climate, such as vegetation (Liang et al., Reference Liang, Russell, Xie, Lupien, Si, Wang, Hou and Zhang2019; Wang et al., Reference Wang, An, Lu, Zhao and Liu2020a). Based on pollen, alkenone, and chironomid records from the TP, Chen et al. (Reference Chen, Zhang, Liu, Cao, Hou, Zhu and Xu2020) were able to confirm a drop in both temperature and precipitation in Middle–Late Holocene times following the Holocene thermal maximum. Alongside this, it was also concluded that in the course of this development, the extent of forested habitat decreased (Fig. 4e).

Figure 4. Spatiotemporal development of climate and fauna in the southern Tibetan Plateau (STP) during the Middle–Late Holocene. (a) Reconstructed annual temperature at midlatitude (30–50°N) based on marine and terrestrial archives (red line; Routson et al., Reference Routson, McKay, Kaufman, Erb, Goosse, Shuman, Rodysill and Ault2019). (b) Effective precipitation reconstructed based on leaf wax δD records of Bangong Co (blue line; Hou et al., Reference Hou, D'Andrea, Wang, He and Liang2017). (c) Mean annual temperature reconstructed by fossil pollen from the TP (red line; Fig. 4D in Chen et al., Reference Chen, Zhang, Liu, Cao, Hou, Zhu and Xu2020). (d) Summer monsoon precipitation reconstructed based on sediment records of Ngamring Tso (light blue line; Conroy et al., Reference Conroy, Hudson, Overpeck, Liu, Wang and Cole2017). (e) Reconstructed forest extent based on arboreal pollen records in the TP (green line; Fig. 9A in Chen et al., Reference Chen, Zhang, Liu, Cao, Hou, Zhu and Xu2020). (f) Variations in the percentage of number of identified specimens (NISP) of wild game in the STP from 5000 to 1000 BP (Supplementary Table D.2). (g) Spatiotemporal distribution of archaeological sites with major exploited animals in the STP (Supplementary Table D.1). Symbols for STP sites correspond to those in Fig. 3.

Despite notable differences in the quality of hitherto recorded faunal data (Supplementary Table D.2), exploitation of animal resources in the STP postdating the Holocene climatic optimum reveal some interesting trends. Figure 4f thus illustrates that relative to human subsistence, the contribution of game species declined over time. Even smaller faunal collections hand-picked during surveys reveal this pattern. Parallel to this, an increase in the number of archaeological sites and the relative contribution of domestic animals to the archaeofaunas is noted (Fig. 4f, g). While climate deterioration undoubtedly affected the natural environment and its vegetation, we postulate that the growing human presence in the study area reflected by increased settlement density and livestock numbers had a lasting impact on natural woodland habitats as well, given that people cut wood for building (houses, fences), cooking, heating, and other purposes. In addition, shepherds pasturing increasingly larger herds at different altitudes and in all vegetation types including forests, certainly contributed over time to the decline of wildlife in local catchment areas.

Interestingly, diachronic analysis of the archaeological record clearly shows that over time, people started exploiting higher elevations more systematically, which would have hardly been possible without adjustments to their subsistence strategy (Fig. 4g). Based on (bio)cultural developments in the STP, three main phases can be distinguished (Fig. 4g). During the first phase (~5.5–4 ka), CSTP and SWTP human groups obviously went on forays above 4400 m asl in search of game. However, communities continued residing at lower altitudes, that is, below 3000 to 3200 m asl in the SETP. Here subsistence relied primarily on foraging and low-level millet and pig farming, as exemplified by Karuo (3100 m asl; BCRTAR&DHSU, 1985) and Xiaoenda (3140 m asl; Zhang et al., Reference Zhang, Chen, Marshall, Lü, Lemoine, Wangyal, Dorje and Liu2019b). Conceivably, the agricultural component of the subsistence dispersed via the Upper Yellow River into the TP, gaining foothold in the SETP ca. 5–4 ka. Though situated at the upper altitudinal and temperature limits for cultivating foxtail millet and raising pigs (d'Alpoim Guedes, Reference d'Alpoim Guedes2015; Keuling and Leus, Reference Keuling and Leus2019), the Karuo villagers obviously participated in small-scale farming alongside a good deal of hunting and gathering. We assume that this represented a viable strategy, because some 5000 years ago, local temperature and precipitation were significantly higher than today (Chen et al., Reference Chen, Zhang, Liu, Cao, Hou, Zhu and Xu2020), by an estimated ca. 1.2°C and 400 mm, respectively (Chen et al., Reference Chen, Dong, Zhang, Liu, Jia, An, Ma and Xie2015a; Wu et al., Reference Wu, Chen, Lv, Brenner, Curtis, Zhou, Chen, Abbott, Yu and Chen2018a). The site's material culture moreover yielded stone tools for harvesting millet, while archaeobotanical analysis confirmed the presence of weeds commonly encountered in millet fields (Lu, Reference Lu2016). Finally, architectural features indicate facilities for millet storage and the stabling of pigs during the cold season.

From the second phase onwards at ~3.8 ka, we observe a significant decline in the role of game in the diet of the TP inhabitants (Fig. 4f). Domestic crops and animals other than millet and pigs become increasingly important in archaeological assemblages, more precisely, wheat, barley, sheep, and cattle. Against the background of shifting climatic conditions, this cultural adaptation makes sense, given the higher ecological tolerance of these crops and livestock species towards colder and drier conditions. Apart from being a reliable food source under these shifting climatic conditions, the mastery of agro-pastoral techniques, including the cultivation of barley at higher altitudes or the hybridization of cattle and wild yak or domestic sheep and wild argali to obtain offspring better adapted to higher altitudes, seems essential in order to significantly advance human exploitation in the TP above 3500 m asl. Archaeological traces bear testimony to these dynamics during the second (4.2–2.7 ka) and third phases (2.7–1 ka), though evidence for village life at altitudes above 3500 m asl remains limited, for example, at Bangga (3–1.8 ka; 3673 m asl; Lu et al., Reference Lu, Chen, Zhang, Tang, Lemoine, Wangdue, Chen, Liu and Frachetti2021) and Dingdong (2.7–2.2 ka; 4100 m asl; CTSSU et al., 2007). Rather, most high-altitude sites discovered and excavated until now represent cemeteries, such as Qugong (3.7–3 ka; 3680 m asl; IACASS and BCRTAR, 1999), Gepa Serual (3.6–2.1 ka; 3780 m asl; Hu, Reference Hu2021a), Butaxiongqu (2.7–2.4 ka; 4650 m asl; Zhang et al., Reference Zhang, Shargan, Lv and Suolang2015); and Gurujia (1.9–1.7 ka; 4300 m asl; Tong et al., Reference Tong, Li and Huang2014). Presumably, the custom of burying the deceased at higher elevations in order to strictly separate them from the living likely has deep roots in Tibetan culture, which believed in preventing evil spirits from threatening the living (Zhu, Reference Zhu1989).

Thus, despite the fact that the current archaeological record does not confirm extensive permanent inhabitation at high-altitude locations, the location of cemeteries nonetheless testifies to regular human presence in this alpine zone, possibly in the context of pastoralism. As observed in montane ecosystems worldwide, vertical transhumance involving upland pasturing in summer and feeding at lower elevation in the valleys during winter is to be expected in the TP as well. In vertical transhumance, usually relatively few people and their herds are involved, with most villagers remaining permanently in the valleys. In the SETP, the sites of Klu lding and Kha lding (Nyingchi area) provide archaeological evidence for such permanent inhabitation at an altitude below 3000 m asl. Bioarchaeological studies at these sites confirm exploitation of pigs, wheat, and sheep, with commensal rodents benefiting from feeding opportunities provided by the human niche.

During the second phase, “eastern” domesticates and crops, that is, pigs and millet, were still exploited in both low-elevation SETP (2900 m asl) and high-elevation CSTP sites (3700 m asl). However, we noted that pigs were a minor source of meat supply in the CSTP (e.g., Qugong) compared with contemporaneous SETP sites (e.g., Klu lding). At Qugong, the remains of “western” crops (wheat and barley) were almost four times (300:83) as abundant as “eastern” ones (foxtail millet and broomcorn millet) (Gao et al., Reference Gao, Yang, Ma, Tong and Yang2021). The low relative abundance of millet and pigs in the assemblages would make it difficult to compensate for losses under fluctuating climatic conditions. In parallel with this, farmers over time may have faced difficulties to cultivate millet and breed pigs at an elevation of 3700 m asl when temperatures dropped. Taken together, regional subsistence patterns characterizing the second phase illustrate an economic emphasis on “eastern” domesticates and crops in the lower SETP and on “western” foods in the higher CSTP and SWTP.

In our three-stage process, the third phase lasting 2.7–1 ka is characterized by the fact that in the archaeological record, two novel large-sized pastoral animals, that is, domestic yak and horses, gain growing visibility (Fig. 4g). By that time, farming communities living at altitudes above 3600 m asl had already shifted crop cultivation in favor of barley at the expense of the less cold-tolerant millet and wheat (d'Alpoim Guedes et al., Reference d'Alpoim Guedes, Manning and Bocinsky2016; Tang et al., Reference Tang, Lu, Spengler, Boivin, Song, Wangdue, Chen, Liu and Zhang2021). Parallel to this, pork had disappeared from the menu as well. Among the newly adopted domestic animals, yak appears locally domesticated (Qiu et al., Reference Qiu, Wang, Wang, Yang, Ma, Wang and Zhang2015), a process likely elicited by hybridization with domestic cattle adapted to montane environments (Medugorac et al., Reference Medugorac, Graf, Grohs, Rothammer, Zagdsuren, Gladyr and Zinovieva2017; Wu et al., Reference Wu, Ding, Wang, Wójcik, Zhang, Tokarska and Li2018b). Conversely, horses, the typical steppe pastoralism animals domesticated first in the Black Sea region (Librado et al., Reference Librado, Khan, Fages, Kusliy, Suchan, Tonasso-Calvière and Schiavinato2021), likely underwent considerable selection during dispersal into high-altitude environments of central and East Asia as well, including improved adaption to conditions of hypoxia (Xu et al., Reference Xu, Luosang, Hua, He, Ciren, Wang, Tong, Liang, Wang and Zheng2007; Liu et al., Reference Liu, Zhang, Li, Pan, Wang, Chen, Zheng, He, Zhao, Pu and Guan2019b). Expectedly, at this stage game did not play a significant role in human food economies anymore. That said, the third phase witnessed the emergence of high-altitude Tibetan pastoralism as we know it today, featuring mainly yaks, horses, and sheep, and the cultivation of barley. Overall, our synopsis fits the three-stage faunal exploitation pattern previously proposed by Zhang (Reference Zhang2016).

Compared with the model proposed by d'Alpoim Guedes et al. (Reference d'Alpoim Guedes, Lu, Li, Spengler, Wu and Aldenderfer2014, Reference d'Alpoim Guedes, Manning and Bocinsky2016) and Chen et al. (Reference Chen, Xu, Chen, Birks, Liu, Zhang and Jin2015b), which shows how shifts in palaeoclimate led to the changes in the crops and land use by Tibetan people, our data suggest palaeoclimate, human activities, and faunal distributions are interrelated in the STP. The cooler and drier climate characterizing the Late Holocene period and continuous exploitation of game during the late Neolithic period (5–4 ka) resulted in a decline of both forest habitat and wildlife, two factors that forced humans to adopt and engage in breeding new livestock species and crops able to better cope with cool and dry conditions. This in turn facilitated the more systematic use of higher altitudes in the STP through pastoralism. In fact, sheep and cattle had already spread to Mongolia and northeast China from the north Eurasian steppe by 5.3 ka (Cai et al., Reference Cai, Zhang, Zhu, Chen, Wang, Zhao, Ma, Royle, Zhou and Yang2018b; Wilkin et al., Reference Wilkin, Miller, Taylor, Miller, Hagan, Bleasdale and Scott2020), but they only appeared in the Yellow River and TP around 1000 years later, as we discussed earlier. The reason why there is such a long time gap before people adopted them was most likely because the agriculturalists and foragers inhabiting the Yellow River Range and TP were still well sustained by their own traditional systems during the sixth and early fifth millennium BP. Humans only started to adopt the new livestock and crops when their own systems were challenged as climate changed and ecological conditions deteriorated. In other words, climatic and ecological change paved the way for a new system exploiting different animals and plants.

The climate change, especially the significant reduction in precipitation, has demonstrably always been directly related to the southward migration of pastoralists during historic times (Bai and Kung, Reference Bai and Kung2011; Pei and Zhang, Reference Pei and Zhang2014). In the STP, we argue that Late Holocene climate change and ecological degradation triggered the adoption and/or development of the new cool-and-dry-tolerant herds and crops. Through introduction of suitable animals and crops, and in case of sheep and cattle improvement through intentional selection and breeding (e.g., hybridizing sheep and cattle with local wild argali and yak respectively), highland domestic herds adapted to the Tibetan alpine ecology and environment were developed, thus contributing to the formation of the highland pastoral system in Tibet.

From the overall data set, we also note that the transitions between the three phases occurred earlier in the NETP than in the STP—in the NETP, the first phase dates to ca. 5.6–4.3 ka and is represented by Majiayao and Zongri culture settlements (Fig. 3, yellow dots), the second phase dates to ca. 4.3–3.5 ka, and is represented by Qijia culture (Fig. 3, orange dots), and the third phase (3.5–2 ka) is represented by Xindian, Kayue, and Nuomuhong culture sites (Fig. 3, purple dots) (Dong et al., Reference Dong, Du and Wei2021; Ren et al., Reference Ren, Yang, Wang, Zhang, Chen, Cui, Wang, Liang and Dong2021). This time lag relates to the fact that sheep and cattle appeared later in the catchment area of the STP. Arguably, once they were incorporated into livestock economies, time was needed for breeding and developing populations adapted to pasturage above 3500 m asl in the STP, which was accomplished by hybridizing domestic lineages of sheep and cattle with argali and wild yak, respectively, giving rise to cold-resistant and hypoxia-tolerant Tibetan sheep, yak, and dzos.

Despite the fact that the large majority of STP sites dating to the later phases exhibit agro-pastoral features, discovery of microlithic assemblages at sites like Zhongba (occupation intervals dated to 6.6–2.6 ka and 3.4–1.3 ka) shows that in the STP, pre-pastoral lithic technology and associated modes of subsistence continued to persist for some time (Hudson et al., Reference Hudson, Olsen and Quade2014). Obviously, communities of foragers and agro-pastoralists coexisted in parts of the TP before the latter displaced the first, as observed elsewhere across the globe (Stephens et al., Reference Stephens, Fuller, Boivin, Rick, Gauthier, Kay and Marwick2019).