The domestication of the horse
The standard zoological indicators of domestication have proven uncertain guides to the identification of the earliest domesticated horses. The wild horses of the mid-Holocene varied naturally in size. The horses of the central Eurasian steppes in Kazakhstan (7-9 in the figure on the right) were somewhat larger than those of the western steppes in central Ukraine (6 on the right), which were larger than those of the steppe/forest-steppe border in western Ukraine and Romania (4-5 on the right), and and all the horses of the steppes were significantly larger than the pony-sized wild horses of central and western Europe (1-3 on the right). Steppe horses were about the same size as later Roman cavalry horses, but in the Eneolithic this made them the largest horses in the world. Any east-west movement of wild horse populations might complicate the detection of size changes caused by domestication.
The increase in variation that began about 2500 BCE, indicated in the graph to the right by the horses of Csepel-Haros in eastern Hungary (#10), continued thereafter. This is often taken as an indicator of domestication beginning at about 2500 BCE (Benecke and von den Dreisch 2003), but increased variation is sensitive to sample size, and in any case the underlying assumptions about controlled breeding for particular types and sizes do not necessarily apply to the earliest stage of horse management.
Levine (1990, 1999) documented different mortality profiles for the horses at Dereivka and Botai, two Eneolithic steppe sites critical for the understanding of early horse domestication. She interpreted both as wild populations, although the Dereivka profile was almost identical to that of the Roman site of Kesteren, where the horses certainly were domesticated. Given these problems with the consistency and even the significance of the standard zoological methods, studies of early horse domestication have fallen back on other indicators.
The earliest possible indicator is the inclusion of horses in sacrificial rituals with domesticated cattle and sheep. Domesticated cattle and sheep were adopted across the western steppes between about 5000-4500 BCE (the tinted region in the map on the left).Horses certainly had a new ritual and symbolic importance in Volga-region sites dated between 5000-4500 BCE. They were the principal meat animal, followed by sheep and cattle, at the contemporary settlements of Ivanovskaya and Varfolomievka. If they were domesticated, these were the oldest domesticated horses.
At the cemetery of Khvalynsk on the Volga River archaeologists led by Igor Vasiliev found 158 human graves dated by radiocarbon about 4500 BCE with the bones of 52 sacrificed sheep/goat, 23 cattle, and 11 horses (Petrenko 1984; Agapov, Vasiliev, and Pestrikova 1990). Animal leg and head parts were offered in all phases of the funerals: on the grave floor, in the grave fill, at the edge of the grave, and in 12 sacrificial deposits stained with red ochre, found above the graves. Horse leg parts occurred by themselves in eight graves. They were grouped with sheep/goat and cattle bones in one grave and in one sacrificial deposit, in rituals that excluded obviously wild animals. 
Khvalynsk
At a contemporary cemetery, S’yezzhe, two horse heads were found in a similar ochre-stained deposit with carved images of horses.
The next possible indicator of domestication is the appearance of horse-head maces in graves in the Dnieper steppes and in the lower Danube valley (tinted below) about 4200 BCE. Graves of the Suvorovo type appeared in the drier, more open parts of lower Danube valley just before the tells of the Karanovo VI-Gumelnitsa-Varna cultures were abandoned in neighboring regions. Polished stone zoomorphic maces were typical prestige objects in the steppes going back to Khvalynsk and Varfolomievka, but were absent from earlier Karanovo or Gumelniţa societies (Chapman 1999). Maces shaped into horse-heads probably were made by people for whom the horse was a powerful symbol. Horses averaged less than 6% of animal bones in Tripolye B1, Gumelniţa, and Karanovo settlements, so were unimportant in Danubian diets. Horse-head maces signaled a new iconic status for horses in the Danube valley just when the Suvorovo graves appeared, 4200-4000 BCE, and just before the abandonment of hundreds of long-established tell settlements. Mounted raiding could have contributed to the Karanovo VI collapse.
By about 3500 BCE the bones of large horses, probably from the steppes, began to appear outside the steppes, in the Danube valley (Bokonyi 1979), in central and western Europe (Benecke 2006), and in the North Caucasus, Transcaucasia, and eastern Anatolia (Bokonyi 1991). At the same time the Botai culture appeared in the steppes of northern Kazakhstan, where several more lines of evidence suggest that horses were domesticated and ridden.
The evidence for riding in the fourth millennium BC
The Botai culture in northern Kazakhstan is named after the site of Botai, where 99% of 300,000 animal bones were from horses. Botai was a culture of foragers that rode horses to hunt horses, a peculiar adaptation found only here and only between about 3600-3000 BCE.
Sandra Olsen’s (2003, 2006) excavations at Botai and Krasnyi Yar found layers of horse dung in house pits, suggesting either stable-cleaning or possibly a roof sealed with horse dung, clear indicators of domestication. Also, whole horse carcasses were butchered in the settlement as a regular practice extending over hundreds of years. Since the Botai culture had no domesticated cattle, they had no animals big enough to drag carcasses, so at least some horses were kept for meat in or near the settlement.
Finally, five lower second premolars from Botai, representing at least three horses, exhibited wear facets of a type that Brown and I have shown are associated exclusively with the use of a bit in mature horses, more than 3 years of age (Anthony, Brown and George 2006; Brown and Anthony 1998). Another site, Kozhai 1, dated to the same period, yielded 46,000 horse bones. We examined 12 lower P2s from mature horses, two of which showed similar wear facets. What kind of bit created these wear facets?
Critics (Levine 2004) have charged that soft bits of rope or leather cannot create wear facets on horse teeth. We conducted a test on four previously never-bitted horses (Brown and Anthony 1998). They were ridden for 150 hours each with bits of hemp rope, horsehair rope, bone, and leather, and we made casts of their P2s at intervals. All bits, including leather, created a wear facet on the lower P2, shown by the steady increase in measurements of the bevel or facet on the lower P2 after 150 hours. Grit trapped under the bit probably was the agent of wear.
Other critics (Levine 2004; Olsen 2006) have charged that identical facets can be found on Pleistocene equids that never were bitted, which would invalidate this kind of facet as a culturally diagnostic feature.
Christian George of the University of Florida recently studied Pleistocene equid lower P2s from the Leisey site in Florida to test this criticism. He used our methods to eliminate teeth from immature equids, 3 years or less, which can have natural irregularities. This left 74 Pleistocene lower P2s from mature equids. We had said, based on the Modern Feral measurements shown at the bottom of the graph on the right, that a facet or bevel equal to or greater than 3mm on a mature equid should not occur in the wild and therefore indicated a pathology caused by a bit.
Among the Leisey P2s George found no bevels greater than 3mm and just one greater than 2.5mm. In contrast, a bevel of 2.5mm or more occurred in the majority (58%) of mature bitted horses, and their maximum was 10mm (shown in the top row on the right with the measurements above the median tinted). George’s study supported a 3mm bevel as a cultural indicator, a threshold we had defined on the basis of a smaller sample of modern never-bitted horse teeth.
Wear facets 3-6mm deep occurred on five P2s from Botai (second row) and two from Kozhai 1 (third row). Combined with the other indicators of domestication, bit wear on multiple teeth from two sites suggests that the Botai people rode horses.
The general increase in the importance of horses between 3500-3000 BCE in Kazakhstan, the Caucasus Mountains, eastern Anatolia, the Danube valley, and Germany; and the appearance in all of those regions of larger horses probably derived from the steppes, suggests that something had changed in the relationship between humans and horses. Botai and Kozhai 1 show what that something was. People had started to ride. Riding might have started earlier, perhaps before 4000 BCE.
THIS PART STILL UNDER CONSTRUCTION
Riding, chariots and warfare
Most observers have emphasized the effects of horseback riding on warfare. But we should differentiate between tribal raiding on horseback, which might have begun before 4000 BCE; and cavalry, which appeared only after 1000 BCE. Steppe bow parts preserved in kurgans of the Eneolithic and Bronze Ages suggest that bows were well over a meter long. Eneolithic arrowheads were made in many sizes and weights. Long bows and non-standardized arrows would have made mounted archery clumsy, although riding might have provided a guaranteed escape after a raid.
In the Ural steppes not too far from Botai, but a millennium later, at least 16 graves of the Sintashta culture contained vehicles with two spoked wheels [image 16] They are dated 2100-1700 BCE. Most contained weapons. A new kind of long stemmed point [image 17], perhaps designed for javelins, appeared in sets of up to 20 in Sintashta-culture chariot graves. Charioteers could stand in a car and hurl a javelin with their entire body while riders could use only their arm, so javelins were more effective from a chariot than from horseback. Bronze Age bows probably were too long for mounted archery.
But around 1000 BCE the short recurved “cupid” bow was developed, and with it new methods for casting socketed bronze arrowheads. The short but powerful bow and the standard-weight arrowhead made mounted archery [image 18] truly deadly. Still, technical advances in bows and arrows were meaningless without a matching change in mentality, in the identity of the fighter, from a heroic single warrior to a nameless soldier. The defining feature of cavalry was that it attacked and retreated as a body in which individual riders became anonymous. An ideological model of fighting that was appropriate for a state, under the leadership of a general, was grafted onto tribal horseback riders.
That shift occurred somewhere in the steppes between about 1000-800 BCE. After it, cavalry swept chariotry from the battlefield and a new era in warfare began.
References
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