The Yamnaya Steppe Herders from Russia

DISCUSSION
A scoring system for assessing horsemanship syndrome and earliest horse riding
Each single trait as described above may not be a specific “occupational marker” for horse riding. The simultaneous occurrence of all six traits in the case of the Strejnicu Yamnaya man, however, gives the interpretation of habitual horsemanship a good degree of plausibility. Apart from our threshold of more than half of relevant diagnostic traits (≥4 of 6 traits) related to biomechanical stress from frequent horseback riding, we applied an additional scoring point system to better assess the degree of symptomatic probability between individuals. This is due to the consideration that a syndrome does not necessarily need to display all correlated diagnostic symptoms, but diagnostic reliability increases with the number of positive symptoms, and some symptoms have a higher and more specific diagnostic value than others. This scoring system (Table 2; see also section S3; the table also provides a summary of the other burials) takes the occurrence of certain traits, their severity of expression, preservation, and relative importance [(22), p. 159] into account. By doing so, we set a second threshold of ≥7 points out of the possible maximum value of 12 (again, more than half).

Besides Strejnicu, particularly the near-complete skeletons of a man of Vetrino (N1, XXXIV/3; fig. S10), 25 to 35 years old at death and a near-coeval dated to 2873 to 2623 calBCE, scores nearly as high, followed by an earlier (2916 to 2881 calBCE) 40- to 50-year-old man of Dévaványa (Barcé-halom, grave 1; fig. S13). Both display pelvic and femoral entheses, acetabular ovalization, femoroacetabular lesions, platymeric femora, and specific vertebral degeneration but lack fall-related traumata. Two more Yamnaya individuals, still displaying four traits, also meet our scoring threshold of ≥7 of 12 points. Of these, the Malomirovo grave 17 (fig. S9) individual, male and 65 to 75 years old, strongly displays the distinctive characteristics and would possibly score higher, if more relevant skeletal regions would be preserved. The Malomirovo and the Balmazújváros (-Kettőshalom grave 1; fig. S11) individuals represent, with radiocarbon dates of 3018 to 2884 and 3021 to 2886 calBCE, respectively, an early Yamnaya horizon.

We also list four more graves meeting the threshold, which are however non-Yamnaya. While the two mature individuals of Medgidia V/4 and VI/6 (figs. S7 and S8) are securely dated to the mid-second millennium BCE, the 25- to 35-year-old man buried in the late fourth millennium BCE in Blejoi III/3 (fig. S6) is culturally displaying a mixture of local elements with those of either pre-Yamnaya or (chronologically possible) incoming first Yamnaya pastoralists (15, 27). Special attention is deserved by the case of the individual of Csongrád-Kettőshalom in Hungary (fig. S12). Displaying five traits, this 25 to 35 years old scores as high as our five Yamnaya individuals and thus meets our requirements to qualify as a rider with a sufficiently high probability. However, his Copper Age date in the second half of the fifth millennium BCE and his geographical isolation call for caution because we lack comparably assessed skeletons of this period and his special cultural context [(42), pp. 249–257; see also section S1 for his Copper Age/Eneolithic context).

A further nine Yamnaya individuals (Table 2), displaying three traits, however, do not meet the requirements set by our scoring system and, thus, fall short for us to plausibly call them riders. The same applies in our set for three more pre-Yamnaya individuals of the late fourth millennium BCE and a Corded Ware man from the Czech Republic (Vliněves, grave 4214A). Besides the men of Medgidia V/4 and VI/6, for which criteria are met, two extra steppe kurgan burials of the mid-second millennium BCE from Bulgaria and Romania also fall short. While we imagine that horsemanship was possibly widespread in the steppes by this time (43), our sample demonstrates that the practice may not always show up reliably in all traits, which is to be expected because of the aforementioned varying influences. This prevents us from securely quantifying horse riding in steppe societies of the third and second millennium BCE. However, having five plausible Yamnaya cases from three different countries in southeast Europe, spanning the near entire duration of Yamnaya culture in these regions, may well speak for a wider practice.
Biomechanical stress markers on human skeletons provide a viable way to further investigate the history of horseback riding and may even provide clues about riding styles and equipment. Depictions of Bronze Age riders (Fig. 5) usually show a position called “chair seat.” This style is mainly used when riding without padded saddle or stirrups to avoid discomfort to horse and rider. It is physically demanding, with the legs exerting constant pressure to cling to the mount’s back and needs continual balancing, but would not preclude activities such as combat or the handling of herd animals, as numerous historical examples demonstrate. The osteological features described here fit well with this riding style and may have been typical for the earliest period of horsemanship. With the later introduction of shaped and padded supporting saddles and stirrups (28), other riding styles such as the so called “split seat,” “dressage seat,” and “hunt seat” evolved (see section S2 and fig. S2).



Fig. 5. Pictorial evidence of horsemanship in the Bronze Age (c. 2100 to 1200 BCE).
(A to C) Mesopotamia. (D to F) Egypt. (G to I) Aegean-Cyprus. (A) Drawing of a seal impression depicting a horse rider, Ur III period (81). (B) Baked clay plaque mold depicting a rider, Old Babylonian period [The Trustees of the British Museum; shared under a Creative Commons Attribution–NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) license; except where otherwise noted, content within this article is licensed under a CC BY 4.0 license] (82). (C) Drawing of a seal imprint of Ili-pada, Middle Assyrian Empire (courtesy of F. Wiggermann, Leiden) (83). (D) Astarte on horseback: an Egyptian graffito, Nineteenth Dynasty (photo credit: S. Steiß, Berlin) (84). (E) Egyptian plaque of glazed steatite showing a horse rider trampling a fallen enemy, Nineteen Dynasty (The Metropolitan Museum of Art) (85). (F) Limestone relief with a messenger on horseback from the Horemheb tomb, Saqqara, Late Eighteenth Dynasty (Museo Civico Archeologico di Bologna) (86). (G) Clay figurine of the so-called “cavalryman” from Mycenae, early LH IIIB (courtesy of J. Kelder, Leiden) (87). (H) Horseman on an LHIIIB krater in the Allard Pierson Museum, Amsterdam (courtesy of J. Kelder, Leiden) (87). (I) Drawing of a sherd showing a horse rider from Minet el-Beida, tomb VI, LH IIIB2 (courtesy of J. Kelder, Leiden) (87).

Together, our findings provide a strong argument that horseback riding was already a common activity for some Yamnaya individuals as early as ~3000 calBCE. This supports other tentative third millennium BCE evidence of an early onset of equines as mounts (44). However, because of the lack of specialized gear and a comparably short breeding and training history, early horses were probably hard to handle. As Librado et al. (1) demonstrate, Yamnaya horses were markedly closer to the equid lineage known as DOM2, including all modern domestic horses, than were wild steppe horses from the sixth millennium BCE. When DOM2 was bred from late Yamnaya horses in the steppes during the second half of the third millennium BCE, genes for reduced anxiety/fear response were selected and retained in all later DOM2 horse breeds. Even DOM2 horses can be highly strung and excitable animals, so a still greater anxiety response in early Yamnaya horses probably made them even more likely to “bolt” from violent or loud actions. The military benefit of equestrianism may therefore have been limited; but nevertheless, rapid transport to and away from the site of raids would have been an advantage, even if combat was carried out on foot. Riding certainly was useful for patrolling wide tracts of land and controlling larger herds of livestock (45). It consequently would have contributed substantially to the overall success of pastoral Yamnaya society.

Table S 5 Phenotype distribution in West Eurasian populations with at least 5 individuals.



To get a better picture of phenotype variation in West Eurasia beyond the Southern Arc we tabulated
phenotype distribution in all populations of our dataset with at least 5 individuals. We infer the presence of depigmented phenotypes in the Southern Arc, listing examples of early regional presence
below:
• Blue eyes were present in the Chalcolithic of the Levant (Israel)(70), Neolithic of
Anatolia (Turkey) at Barcın(5) and Chalcolithic at Arslantepe and Çamlıbel Tarlası(30), and
Chalcolithic Southeastern Europe (Romania at Bodrogkeresztur).
• Blond hair was present in the Neolithic of Anatolia (Turkey) at Barcın(5), Chalcolithic
Southeastern Europe (Romania at Bodrogkeresztur), Chalcolithic of the Levant (Israel)(70), and
a Minoan from Lasithi.(4)
• Pale skin was inferred for Chalcolithic Southeastern Europe (Romania at
Bodrogkeresztur), Iron Age Iran (Hasanlu), Croatia and Bulgaria, and Late Bronze Age
Montenegro.

Did steppe groups possess these traits to a higher frequency than the inhabitants of the
Southern Arc?
Blue eyes were not inferred for all 19 individuals of the Yamnaya cluster examined (Table S
4) and for 1/15 individuals of the Afanasievo culture. They were found at a higher frequency
(~29-55%) at the later Middle-to-Late Bronze Age samples of the Srubnaya, Sintashta cultures
and at Krasnoyarsk in Russia(5, 33, 23, 71, 72) and Kazakhstan (Aktogai and Maitan
Alakul),(52) i.e., populations with elevated Anatolian/European farmer ancestry.(5) They were
also present in Early/Middle Neolithic farmers from Central Europe including the LBK (first
farmers of central Europe) and Globular Amphora culture,(73) and at the highest observed
frequencies in farmers from Scandinavia and the Baltics (EBN Narva in Lithuania(74) and
Motala in Sweden(5, 10, 34)). Similarly, blond hair was inferred for 1/34 individuals of the
combined Yamnaya and Afanasievo cluster, but reached ~14-60% in the aforementioned later
steppe groups. Interestingly, light pigmentation phenotype prevalence was nominally higher in
the Beaker group than in Corded Ware than in the Yamnaya cluster (where as we have seen it
was rare), in reverse relationship to steppe ancestry, and thus inconsistent with the theory that
steppe groups were spreading this set of phenotypes.

As for the category of pale skin that is very limited in samples from the Southern Arc as a
whole (1.7%), it appears to have been rare in all the studied samples in general, exceeding 1/4 in
frequency only in Medieval Germany, Saxons from England, Central European outliers from
Late Antique Italy, Pre-Christian Icelanders, with the earliest high frequency found in Bronze
Age Latvians at 37.5% (3/8).

Our survey of pigmentation phenotypes is not meant to be a comprehensive treatment of
how these varied in space and time, but we highlight three key observations:
• The modal phenotype of the Southern Arc and West Eurasia was as expected one with
dark hair, eyes, and intermediate skin pigmentation, similar to other Eurasians.
• The distinctive depigmentation found in modern groups was not associated with a
particular type of ancestry in the past, as light eyes and hair were found in both West Asia and
Europe, and among early farming, steppe pastoralist, as well as hunter-gatherer groups.
• The frequency of these traits could have been shaped by migration or by selection, but is
more complex than simplistic stories, e.g., of these traits arising due to sexual selection in boreal
hunter-gatherers(75) or spread by steppe Indo-Europeans.(68)

Surveying the history of thought on human pigmentation differences, we can remark that the ancient writers of the classical world more or less accurately described the average lighter pigmentation of populations of central/northern Europe and the Eurasian steppe, although they lacked the statistical vocabulary to express these in relative terms and exaggerated what various ancient groups (such as the “Celts” or “Scythians”) looked like. Their theory that these differences were linked to climate was fundamentally flawed, as we know that people with quite different pigmentation lived in more less similar conditions of e.g., central Europe at the time of the farmers or the medieval period or the steppe in the Early Bronze Age or the time of the Scytho-Sarmatians with which they were familiar.
The promulgators of the Aryan myth also started with the present-day distribution of pigmentation phenotypes and came to a different conclusion: that these were not due to climate dictating a different phenotype for the cold north and temperate south, but rather of the existence of a primordial “race” of pale, blond, blue-eyed Proto-Indo-Europeans spreading their languages together with their phenotypes. Thus, they extrapolated the phenotype of some of their contemporaries and medieval ancestors backwards in time, postulating that it was a survival from the remote past that had decreased in frequency as this supposed “race” encountered and admixed with other populations. On the contrary, our survey of ancient phenotypes suggests that aspects of this phenotype were distributed in the past among diverse ancestral populations and did not coincide in any single population except as isolated individuals, and certainly not in any of the proposed homelands of the Indo-European language family.

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