NEW YORK – A team from France, the US, and other international sites has garnered ancient genetic evidence that is inconsistent with horse domestication in Anatolia, instead pointing to the introduction of already domesticated horses into Anatolia and other parts of the southern Caucasus.
"The ultimate geographic origins of the imported domestic herds remain to be determined, but eliminating Anatolia as a source of domestication directs further attention to the adjacent regions of the Black Sea," co-senior and corresponding author Eva-Maria Geigl, a University of Paris researcher, and her colleagues wrote in their Science Advances study, published on Wednesday.
There, they outlined efforts to characterize more than 100 ancient equid samples stretching over some 9,000 years, spanning the early Neolithic Age to the Iron Age, from eight central Anatolian sites and half a dozen sites in other parts of the Caucasus.
"Despite the important roles that horses have played in human history, particularly in the spread of languages and cultures, and corresponding intensive research on this topic, the origin of domestic horses remains elusive," the authors wrote, noting that "[s]everal domestication centers have been hypothesized, but most of these have been invalidated through recent paleogenetic studies."
With that in mind, the researchers focused on a region known for its historical reliance on horses, using an optimized metabarcoding-based sequencing strategy, targeted mitochondrial DNA and Y chromosome sequencing, and informative SNP genotyping to interrogate 111 equid samples collected in Anatolia and the Caucasus from time points that span the estimated horse domestication window around 5,500 years ago.
Using data from the 77 ancient samples that were successfully genotyped, the team saw a sharp genetic transition from equids that were free from domestic horse haplotypes to those showing signs of domestic horse mixing.
"Our results strongly suggest that Anatolia was not a primary source for domestic horse lineages," the authors wrote, "but, as observed in other regions, local matrilines were incorporated into herds of imported domestic horses, which were also hybridized with local donkeys to create mules."
In a dozen Anatolian horses going back around 4,500 years, for example, the researchers identified mitochondrial haplogroups that appeared to represent local wild horse populations and were not found outside of the region. Though local maternal lineages persisted over time, an influx of new mitochondrial haplogroups appeared in the area within the past 2,200 years, pointing to the arrival of horses domesticated in another part of the world.
The team noted that the newly arrived domestic horses brought with them features not found in the local wild horses, leading to a more extensive range of coat colors in the horses in the region as introduced domestic steeds mixed with local mares.
These and other findings indicate a nearly complete population turnover from the late third millennium before the common era onward and correspond well with iconographic and textual evidence for the appearance and dispersal of horse management in Anatolia and Mesopotamia, the authors noted.