Rethinking the evidence for early horse domestication at Botai

Abstract

Despite its transformative impact on human history, the early domestication of the horse (Equus caballus) remains exceedingly difficult to trace in the archaeological record. In recent years, a scientific consensus emerged linking the Botai culture of northern Kazakhstan with the first domestication of horses, based on compelling but largely indirect archaeological evidence. A cornerstone of the archaeological case for domestication at Botai is damage to the dentition commonly linked with the use of bridle mouthpieces, or "bit wear." Recent archaeogenetic analyses reveal, however, that horse remains from Botai are not modern domesticates but instead the Przewalski's horse, E. przewalskii-warranting reevaluation of evidence for domestication. Here, we compare osteological traits hypothesized to have been caused by horse transport at Botai with wild Pleistocene equids in North America. Our results suggest that damage observed in Botai horse teeth is likely generated by natural disturbances in dental development and wear, rather than through contact with bridle equipment. In light of a careful reconsideration of the mid-Holocene archaeological record of northern Eurasia, we suggest that archaeological materials from Botai are most effectively explained through the regularized mass harvesting of wild Przewalski's' horses-meaning that the origins of horse domestication may lie elsewhere.

Figure 1

Geographic location of Botai (right) and North American Pleistocene sites (left). Site abbreviations: B = Bluefish Caves, BD = Blackwater Draw Loc. 1, C = Cedral, D = Dry Cave, E = Edmonton area gravel pits, I = Isleta Cave No. 2, J = San Josecito Cave, K = Dark Canyon Cave, N = Natural Trap Cave, Q = Cueva Quebrada, R = Scharbauer Ranch, S = Salt Creek, W = Wally’s Beach. This map was generated using the open- source software qGIS (https://www.qgis.org/en/site/), version 3.18.

Figure 2

Botai horse tooth cited as conclusive evidence of bit wear in Outram et al., showing the existence of two overlapping areas of enamel exposure corresponding to areas of reduced cementum deposition along the buccal and lingual margins.

Figure 3

Comparison of the Botai “bit wear” specimen (center) with a similar tooth from a Pleistocene wild horse from North America (specimen n^o MgVo-1: K8-1-2; Canadian Museum of History) that exhibits anterior enamel pits with dentine exposure (left) and cementum banding on both the buccal surface (right) and the lingual surface (not pictured).

Figure 4

Schematic diagram of two longitudinal histological sections showing the differences between (A) a pit-form hypoplastic defect and (B) a pit produced by other processes such as flaking of poorly mineralized enamel or enamel erosion due to mechanical wear. (A) In a pit-form hypoplastic defect the rim of the pit is smoothly curved and the striae of Retzius in the enamel forming the walls of the pit are also curved. (B) A pit produced by flaking of poorly mineralized enamel or enamel erosion due to mechanical wear cross-cuts normal striae of Retzius and it usually lacks a smooth and curved rim. E = enamel; D = dentine; lines in enamel represent striae of Retzius.

Figure 5

Mandibular bone formation on wild Pleistocene horse (specimen n^o DhPg-8: 861.1; Royal Alberta Museum) from Wally’s Beach, Alberta, earning a score of “2” on the system devised by Bendrey.