The extreme rarity of stratified and directly-dated faunal assemblages linked to the early pastoral period make our new discoveries especially significant in understanding the transition to herding economies. Across Mongolia, consistent and severe wind deflation and aridity conspire to produce a near-total absence of buried habitation sites68, while those which are recovered typically lack associated or dated faunal remains. Consequently, while our excavated structure at Bagsagiin Bulan does not have securely associated faunal material, it nonetheless provides a rare, direct window into the lifeways of people at the transition to herding economies in eastern Inner Asia. More importantly, although our newly identified assemblages at Tsagaan Asga and Biluut are small and conclusions must be drawn cautiously, these data points provide the very first securely dated insights into the economic use of domestic animals prior to the final Bronze Age.

Archaeological materials from Bagsagiin Bulan show the presence of stone tools and a tent-like structure, hinting at a mobile lifeway rooted in earlier hunter-gatherer traditions ca. 2500 BCE. Herding is practiced in the Darkhad Basin area around Bagsagiin Bulan today, but the region straddles the steppe-boreal forest ecotone, and might be most appropriately characterized as part of broader Baikalia - a well-watered area with rich wild game, timber, and natural resources. Although our excavations provided no faunal data reliably associated with the site’s occupation, across the Russian border to the north, recent work demonstrates that hunting and gathering persisted along the shores of Baikal until a cultural disruption associated with the incursion of pastoralism during the late second and early first millennium BCE69,70.

Our newly excavated and analysed archaeofaunal assemblages from western Mongolia provide direct evidence for pastoral economies during the Middle Bronze Age. Faunal assemblages from Biluut and Tsagaan Asga yielded only Ovis, indeterminate caprine, or Bos remains. The strict focus on these taxa suggests that pastoral herding was practiced in the Mongolian Altai by the late third and early second millennium BCE. Although these two localities are the only domestic sites dated to the Bronze Age in the Mongolian Altai yet known, horse bones have been recovered from within Chemurchek ritual sites such as Poligon I, dated to ca. 1720 BCE (3370 +/− 350 cal BCE, median date 1718 cal BCE, ca. 2626–833 cal BCE 2-sigma calibrated range46). DNA analysis will be necessary to assess whether these remains came from the lineage of the domestic horse (E. caballus) or other lineages of wild or proto-domesticate animals. However, their occurrence in this ritual context provides compelling reason to suspect that pastoral people had domestic horses at the time that these sites were occupied, during the early second millennium BCE. Nonetheless, faunal assemblages from Tsagaan Asga and Biluut provide no support for the idea that horses made a meaningful dietary contribution to the diet of Early and Middle Bronze Age pastoralists.

The data from these three sites point to incipient pastoral cultures building sturdy occupational structures, and using horses in occasional ritual contexts – but not yet any evidence for a dietary role - mirroring patterns observed in more westerly areas of Central Asia22,67. Extant faunal assemblages from the small handful of documented domestic contexts in Mongolia indicate that horses became a key component of diet sometime during the Bronze Age39,71, a pattern mirrored in their frequency in ritual assemblages33. The lack of physical structures associated with later periods also implies a shift towards mostly ephemeral habitations and an increased level of mobility during this period39. While available samples are small (as dictated by the region’s fragmentary archaeological record) our data thus suggest an Early and Middle Bronze Age pastoral economy that differed markedly from the specialized, horse-focused pastoralism that characterizes later periods– in which these animals played a crucial role in diet, movement, and culture.

Changes in the location of ritual structures, monuments, and burials across the Bronze and Early Iron Ages imply a dramatic increase in the exploitation of dry, intermontane and open steppe regions during the second millennium BCE that may reflect changes in mobility associated with horse riding (Fig. 8). The Early and Middle Bronze Age were particularly dry in many areas of central and western Mongolia after 3000 BCE72,73,74, which may have driven down wild game abundance and made pastoral subsistence more attractive. With comparatively higher rainfall and seasonally productive food and water sources at high altitude, the high mountainous regions of Mongolia would have been the most stable and viable regions for pastoral herding – particularly if mobility was comparatively limited by the lack of mounted horseback riding. These mountain regions are the primary locations for chariot petroglyphs in Mongolia, which are not typically found in the country’s eastern reaches75. Although other non-cultural explanations such as the availability of suitable geology for rock art preservation in the Altai region could also explain this pattern, a shift towards widespread occupation of intermontane regions may be plausibly associated with the increased mobility associated with mounted horseback riding. The apparent fluorescence of pastoral occupation of steppe and steppe-desert regions may also reflect the unique ecological benefits of dry steppe associated with horse herding, including increased herd yields and improved health for animals moved over long distances in these areas17.

Figure 8 (A) Early and Middle Bronze Age archaeological sites (Afanasievo Chemurchek, and Munkhkhairkhan, ca. 3000–1500 BCE) and (B) Post-1200 BCE Late Bronze and Early Iron Age archaeological sites (DSKC and Slab Burial cultures) plotted against digital elevation model of Mongolia, with low elevation of 500 m shown in red, and high elevation (2500 + m) shown in blue. Data from Eregzen (2016). Icons in upper right show hypothesized horse transport technology in use during each period. Full size image

Our data – the first habitation sites of their kind with detailed taxonomic identifications from the early Bronze Age of Mongolia – support inferences from meta-analyses indicating that while pastoralism was practiced in parts of Central Asia and Mongolia by the early Bronze Age, the adoption of horse riding prompted dramatic alterations to the ecology of herding economies during the end of the second millennium BCE. Considering the distribution of documented monument sites across the Bronze Age, we hypothesize that the innovation or local adoption of horseback riding prompted a shift from localized transhumant exploitation of montane zones, with economies perhaps focused on sheep and cattle, to a more diverse pastoral economy where horses played a crucial role as livestock (Fig. 9). This pattern of horse-based subsistence and high residential mobility persisted from the DSK period through the time of the Mongol Empire76 and up to the present day77.

Figure 9 Idealized model for the impact of horse transport on pastoral lifeways in Mongolia during the late Bronze Age. Blue denotes hunting and gathering subsistence, red denotes low-mobility pastoral subsistence, and green denotes horse-based, high mobility pastoral subsistence. The top figure shows the clustering of pastoral lifeways in montane regions of western and central Mongolia during early and middle Bronze Age, and the bottom figure shows the widespread geographic distribution of Late Bronze Age and Early Iron Age pastoral sites, concurrent with both early evidence for horseback riding as well as increased economic exploitation of horses. Full size image

Horses and herding transformations across central asia

The most compelling support for a transformation in the role of domestic horses observed in the Mongolian archaeological record at the end of the second millennium BCE comes from contemporaneous patterns in published archaeofaunal assemblages from western regions of Central Asia – indicating that this shift was both real and broad geographic significance. The available data support the idea that the incorporation of horses into chariot technology prompted the initial integration of domestic horses into pastoral lifeways for many Bronze Age Central Asian herders, as implied by Kohl28 and others. Horses and their secondary products (as suggested through lipid analysis of milk in ceramics) were likely still used in ritual activity during the early second millennium BCE, but they declined in general visibility in archaeological assemblages during this time22, and likely served a limited economic or dietary role66. In contrast, and as noted earlier by scholars working in areas such as SE Kazakhstan (e.g.6,67) a recognizable pattern of increase in horse remains at many sites is visible at the end of the second millennium BCE across a broad geographic region.

Some researchers (e.g.11) have rightly highlighted the potential discrepancy between the number of horse bones recovered from a given archaeological assemblage, and actual frequency of animals kept by a given group. In many contexts, riding horses have been kept in large numbers without leaving a corresponding zooarchaeological signature. Therefore, the frequency of horse bones found at any given site is, on its own, a poor reflection of the extant horse population associated with the site’s inhabitants. Nonetheless, our data indicate that at the end of the second millennium BCE, some areas witnessed saw dietary exploitation of domestic horses to a previously unforeseen extent, and that all study regions saw a general trend towards higher frequencies of horse bones in zooarchaeological assemblages. Acknowledging that %NISP is an imperfect measure, we argue that this pattern – increased dietary reliance on horses at many locations across the Eurasian Steppe – reflects the ability to control larger herds of horses initiated by the innovation of mounted horseback riding. In some cases, the ability to control more horses appears to have prompted an increased dietary reliance on horses as a source of meat – causing an increase in the frequency of horses in many archaeofaunal assemblages. It must be noted that broad-scale environmental differences between regions6, as well as cultural and microenvironmental factors7, are important influences on the composition of Central Asian herds and archaeofaunal assemblages. Compellingly, however, the pattern of increased frequency of archaeological horse remains during the late second millennium BCE can still be observed within various regions - including in the Trans-Ural region, the Central Steppes of Kazakhstan, and the arid desert-steppes of southern Central Asia (Fig. 7).

Together, this broad summary of extant scholarship supported by new data from Mongolia point to a pronounced increase in the numbers of horses used by pastoralists across multiple different ecozones of Central Asia at the end of the second millennium BCE. Aligned with a growing body of scholarship linking this period with the adoption of riding both in Mongolia35,36,37,75 and more broadly across Central Asia25,28,67, our results support a direct link between increased economic reliance on domestic horses and the emergence of mounted riding among East or Central Asian pastoralists – ca. 1200 BCE. This proposed link between riding and economic exploitation of horses helps to explain the limited economic and mortuary presence of horses noted in the Central Steppe22,78 and corroborated from our initial results in Mongolia.

Implications: bronze age mongolia and LBA dispersals

A Late Bronze Age origin for mounted horseback riding may explain very important, broad-scale cultural and biological patterns across Inner Asia. Recent genomic sequencing efforts place the DSK horse as one of the most basal lineages among ancient domestic horses studied to date21. Spatial analysis of modeled radiocarbon dates indicates a rapid geographic expansion of horse sacrifice at DSK monuments across the Eastern Steppe33, concurrent with some of the oldest direct evidence for mounted horseback riding (equine osteological changes) from these same DSK horses36. Although these data come primarily from ritual contexts, our new data from early Bronze Age campsites seem to show a similar pattern mirrored in dietary assemblages. Deer Stones are recognized as the earliest clear progenitor for ‘animal-style’ art, a style that spread across most of Central Asia during the first millennium BCE32,79. Recent large-scale genomic research suggests that the expansion of DSK culture and later diffusion of animal art style co-occurred with westward gene flow into western Eurasia from proto-“Scythian” peoples in eastern Inner Asia during the first millennium BCE80. The innovation of mounted riding in Central or East Asia, and subsequent outward dispersal of human groups provides one compelling hypothesis to explain both westward gene flow and cultural transmission of animal style. In fact, recent careful experimental study of the use-wear patterns on second millennium BCE horse equipment from Central Asia points to the latter half of the second millennium BCE as the earliest possible date for widespread riding26. Recent human genomic data from DSK populations in northern Mongolian link these groups with ancestral Northeast Asian/Siberian hunter-gatherers81. The outward dispersal of these groups into westerly areas of Eurasia during the LBA, linked with the innovation or adoption of mounted horseback riding could thus explain the mixed pastoralist/hunter gatherer signal evidenced in many early Iron Age Saka/Scythian groups80.