The nomadic peoples of the Eurasian Steppes have long been a source of fascination to both archaeologists and the general public, with, sometimes less than flattering, fictionalised versions appearing in popular fantasy novels such as JRR Tolkien's Lord of the Rings and GRR Martin's Game of Thrones. The later phases of these groups, such as the Xiongnu and Mongol Empires are relatively familiar, but the origins of these groups in the Eneolithic (the Late Neolithic plus the Chalcolithic, or 'Copper Age') are rather more obscure. The archaeology of these groups has been studied for a long time, but new technologies have recently shed new light on the field. For example, it has been demonstrated that European populations had a significant influx of DNA from steppe-dwelling groups during the late Neolithic. The same Neolithic steppe populations (referred to as Yamnaya by archaeologists) also have also been shown to have genetic links to the Afanasievo people of the Altai Mountains and even the peoples of Mongolia. Both archaeological and genetic data suggest extensive population movements in this area during the Early Bronze Age (roughly 3300 to 2500 BC), with links being established between the Yamnaya peoples of the Pontic–Caspian steppe and the peoples of Siberia and Scandinavia.
Thus, it is understood that the Yamnaya peoples underwent a significant expansion of their geographical range during this period, but the drivers of this expansion are less certain. One popular explanation is that innovations such as the use of Horses and wagons enabled the rapid spread of a pastoralist lifestyle across large swaths of Eurasia, and that this, combined with the consumption of dairy products, made large areas of the Eurasian steppes previously unoccupiable open to Human habitation. However, while this model provides a plausible explanation for the successes of the Yamnaya peoples, it is not, at the current time, very well supported by the available evidence. There is archaeological evidence for the use of carts and bridles in the Eneolithic and Early Bronze Age, but not for the use of Horses or dairy products.
The story of Horse domestication has long been a controversial subject in archaeology. Horse remains are known from the Eneolithic of Botai in northern Kazakhstan, but these have recently been shown to have been Przewalski's (or Mongolian) Wild Horses, Equus przewalskii, not the modern domestic Horse, Equus caballus, a species which has not confidently been found in association with Humans at sites older than the Early Bronze Age, and which cannot be confidently asserted to have been used as a riding Animal or even a beast of burden, rather than something which was being hunted, at Early Bronze Age sites. It is currently thought that Horses were not ridden, or milked, on the Eastern European steppes before about 1200 BC, and they may not have been an Animal used much by the pastorialist peoples of the period at all.
Data on the early consumption of milk is equally lacking. Isotopic studies of Human remains have been used to suggest that dairy products were being consumed, but cannot confirm this. Palaeoproteomics (the analysis of ancient sets of proteins) could potentially be used to identify dairy consumption, but so far has only been applied to a very limited number of sites on the Eurasian steppes. Studies of the Yamnaya and Afanasievo peoples have only, to date, shown evidence of dairy consumption among a few individuals from the Eastern Steppes, and was only able to give a very ambiguous result on the producer of the peptides (short amino acid chains, or fragments of proteins) found, which was probably a Sheep or Cow.
In a paper published in the journal Nature on 15 September 2021, a group of scientists led by Shevan Wilkin of the Department of Archaeology at the Max Planck Institute for the Science of Human History, and the Institute for Evolutionary Medicine at the University of Zürich, present the results of a study which examined palaeoproteonomic evidence from dental calculus from 56 Humans from across the Eurasian steppes, dated to between 4600 and 1700 BC.
Wilkin et al. collected data from 19 Eneolithic idividuals; six from Murzikha 2, nine from Khvalynsk 1 and Khvalynsk 2, one from Ekaterinovka Mys, one from Lebyazhinka 5, and two from Khlopkov Bugor. Studies of Ancient DNA obtained from Khvalynsk and othe Eneolithic burrials in this area of the the Volga and northern Caucasus, suggest that the local population was related to the Yamnaya Peoples, but lacked the input of genetic materials from Anatolian farmers seen in the later.
Studies based upon archaeological evidence and stable isotope analysis have suggested this population had a diet based upon the gathering of local plants, fishing, and the consumption of domestic Animals. Wilkin et al. also extracted dental calculus from two individuals from Botai in northern Kazakhstan, a site dating to about 3500 BC, where faunal remains are dominated by domestic Horses, and proteins extracted from ceramics have suggested Horses were being milked.
Map showing sites that yielded individuals with preserved ancient proteins. (a) Eneolithic, (b) Early Bronze Age and (c) Middle–Late Bronze Age sites in the Pontic–Caspian region, showing the number of individuals with a positive dairy identification out of the total number of individuals with preserved ancient proteins for each site. Strong evidence of preservation of Equine or Ruminant milk protein identifiers are depicted with black Animal icons; the single individual with equivocally identified casein peptides is shown with a grey icon. Wilkin et al. (2021).
In addition, Wilkin et al. sampled 35 Bronze Age Humans from 20 sites. These include sixteen Early Bronze Age individuals; two from Krasikovskyi 1, one from Krasnokholm 3, two from Krivyanskiy 9, two from Kutuluk 1, one from Leshchevskoe 1, one from Lopatino 1, two from Mustayevo 5, one from Nizhnaya Pavlovka, one from Panitskoe, one from Podlesnoe, one from Pyatiletka, and one from Trudovoy; as well as fourteen individuals the Middle–Late Bronze Age transition; one from Bolshekaraganskyi, two from Kalinovsky 1, three from Kamennyi Ambar 5, one from Krasikovskyi I, three from Krivyanskiy 9, one each from Lopatino 1 and Lopatino 2, one from Potapovka 1, one from Shumayevo 2, and five from Utevka 6.
Previous archaeological isotopic studies of Early Bronze Age Yamnaya sites have suggested a diet strongly focused on herd Animals, including Cattle, Sheep and Goats. Horse remains have also been found at Early Bronze Age Yamnaya sites, but whether these were domestic Animals or wild Horses hunted for their meat is unclear. The Middle–Late Bronze Age transition was marked by an increased use of Horse-based technologies, such as chariots, which clearly indicates these people were using domestic Horses.
Fifty five of the fifty six dental calculus samples tested yielded identifiable protein data, and forty eight of those produced strong enough signals of proteins commonly found in the oral cavity that they were included in the study.
The nineteen oldest individuals examined, all dated to between 4600 and 4000 BC, came from five Eneolithic sites close to the Volga River, or tributaries of that river, in southwestern Russia. Of these nineteen, eleven yielded good enough data to be included in the final study, with ten showing no evidence for the consumption of dairy products. The remaining individual yielded to peptides associated with Bovine α-S1-casein milk curd protein, although Wilkin et al. do not take this as absolute proof of milk consumption, as the most common dairy protein, β-lactoglobulin, was not recovered. Neither of the Botai individuals returned any evidence for dairy consumption.
Fifteen of the sixteen Early Bronze Age individuals included in the study yielded multiple Ruminant dairy peptides including β-lactoglobulin, with some also producing α-S1 casein, α-S2-casein or both. Many of these peptides were identifiable to genus level, with the most common genera being Ovis (Sheep), Capra (Goats), and Bos (Cattle, Buffalo, Bison, and Yaks, although presumably Cattle were the most likely milk-producers). Interestingly, two individuals, both from Krivyanskiy 9, on the southwestern fringe of the study area, yielded Equus (Horse, Donkey and Kiang, although only Horses would have been present in the study area) β-lactoglobulin. These individuals were estimated to have died between 3305 and 2633 BC.
Histogram of taxonomic specificity of dairy peptide spectral matches per individual. Histograms for individuals with evidence for consumption of dairy, from the Eneolithic (a), Early Bronze Age (b) and Middle and Late Bronze Age (c). PSM, peptide spectral match. Wilson et al. (2021).
Fifteen of the nineteen Middle–Late Bronze Age transition yielded positive evidence for the consumption of Bovine milk products, including peptides from β-lactoglobulin, α-S1-casein and α-S2-casein, and the whey protein α-lactalbumin. It was possible to identify some of these peptides as being Ovis or Bos, but both Capra and Equus were absent from the sample.
Wikin et al.'s results point to a clear shift towards milk consumption between the Eneolithic and Early Bronze Age, with 10 of 11 Eneolithic individuals showing no evidence of dairy consumption, whereas 15 of 16 Early Bronze Age individuals showed such evidence. A single Eneolithic individual, from Khvalynsk, showed possible evidence of dairy consumption, but this result cannot be taken with any confidence. This strongly suggests that the widespread adoption of dairy products as part of the Human diet was associated with the Eneolithic-Early Bronze Age transition on the Pontic–Caspian Steppe. This is in contrast to the situation to the west, where settled European farmers were clearly consuming dairy products in the Eneolithic. This in turn suggests a cultural frontier between the European farmers and the Steppe herders.
The ability of proteonomics to identify the Animals producing the milk used for Human consumption sheds light on the Animals being kept by these peoples. The Pontic–Caspian Steppe provides a rich environment capable of supporting a range of herd Animals, including Cattle, with a relatively high water-demand, and Sheep and Goats, which favour more arid conditions. Interestingly, a recent study of Early Bronze Age individuals from the steppes suggests that the persistence of lactase (the enzyme that allows digestion of whole milk) production into adulthood in these individuals was rare, but this does not rule out the production of milk-derived products such as yogurts, cheeses or fermented milk beverages.
The milking of Horses has previously been suggested for the Botai culture of Kazakhstan, but Wilkin et al. found no evidence of this (although their sample size, two individuals, was quite small). Horse milk was apparently consumed by two individuals from the Early Bronze Age of the Pontic–Caspian Steppe. These findings, combined with the discovery that the Horses of Botai were not the Domestic Horse, Equus caballus, supports the idea that Horse domestication originated on the Pontic-Caspian Steppe rather than with the peoples of Central Asia. The oldest Horse remains shown to contain genetic markers for modern domestic lineages date from between 2074 and 1625, and come from sites in Russia, Romania and Georgia. The discovery of the oldest known evidence in the Pontic-Caspian Steppe region, which also saw the first appearance of Horse-drawn chariots around 2000 BC, contributes further evidence to this hypothesis.
Wilkin et al.'s findings contribute to the growing understanding of a significant cultural and technological revolution associated with the Eneolithic-Early Bronze Age transition on the Pontic-Caspian Steppe. As well as the, obvious, adoption of bronze as a metal for making tools and weapons, this shift included the abandonment of riverine settlement sites, the appearance of kurgan cemeteries on formerly uninhabited arid plateaus, the appearance of wheeled vehicles, and the occasional placement of Horse bones in Yamnaya burials. This was accompanied by a rapid expansion of the range of these peoples, both to the west into Europe and to the east into the Altai Mountains. Wilkin et al.'s findings shed no direct light upon the role of Horses in this expansion, but evidence for the consumption of Horse milk is clearly evidence for Horse domestication, which is likely to also imply Horses were being used for other purposes. The combination of a dietsry shift to include nutritionally rich dairy products, the adoption of Animal-drawn vehicles as a means to transport greated loads, and the domestication of highly versatile Horses is likely to have significantly transformed the cultural and economic environment of the Pontic-Caspian Steppe, enabling Humans to venture into previously uninhabitable areas, and thereby access further new resources, such as seasonally snow-covered upland pastures. It is, of course, possible that all of these elements were present to some extent before the Eneolithic-Early Bronze Age transition, but that transition clearly shows the widespread adoption of all these technologies by populations over a wide geographical area.
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