Ancient DNA shows domestic horses were introduced in the southern Caucasus and Anatolia during the Bronze Age

Abstract

Despite the important roles that horses have played in human history, particularly in the spread of languages and cultures, and correspondingly intensive research on this topic, the origin of domestic horses remains elusive. Several domestication centers have been hypothesized, but most of these have been invalidated through recent paleogenetic studies. Anatolia is a region with an extended history of horse exploitation that has been considered a candidate for the origins of domestic horses but has never been subject to detailed investigation. Our paleogenetic study of pre- and protohistoric horses in Anatolia and the Caucasus, based on a diachronic sample from the early Neolithic to the Iron Age (~8000 to ~1000 BCE) that encompasses the presumed transition from wild to domestic horses (4000 to 3000 BCE), shows the rapid and large-scale introduction of domestic horses at the end of the third millennium BCE. Thus, our results argue strongly against autochthonous independent domestication of horses in Anatolia.

Fig. 1. Comparative maximum likelihood phylogenetic analyses of horse mitogenome using either the complete mitogenome sequences (left side) or the concatenated mitogenome fragments used for genotyping ancient remains (right side).

The nomenclature of the horse mitochondrial haplogroups from A to R is as defined by Achilli et al. (47). Haplogroup S corresponds to an additional haplogroup obtained when adding Przewalski’s horse sequences not belonging to the F haplogroup (98). The scale bar represents the number of nucleotide substitution per site as indicated. The branches separating horse, hemione, and donkey sequences are not drawn to scale as indicated by the intersecting parallels. A magnified view of the O-P-Q subtree of the concatenated fragments is represented in the box on the right side. The magnified view additionally reveals the position of the X sequence found in two ancient Anatolian remains. The numbers by the nodes indicate their corresponding bootstrap values.

Fig. 2. Mitochondrial and coat color diversity before (top) and after (bottom) 2000 BCE.

(Left) Evolution of mitochondrial haplotype diversity of horses in Anatolia and the southern Caucasus. (Right) Evolution of coat color genetic diversity in these two geographic regions in the same time ranges. The area of the circles is proportional to the number of individuals present in each category.