Late Iron Age and Roman equine breeding north of the Alps: Genetic insights and cultural implications

The Roman conquest of the northern Alpine foreland in 15 BCE introduced larger-sized horses and hybrid mules to the region. To investigate their genetic profiles and influence on local breeding, we analyzed our previously generated shallow shotgun DNA data from 402 Late Iron Age and Roman equids, supplemented with mitochondrial and nuclear capture data from 40 to 31 equids from the same regions and periods. Late Iron Age and Roman horses exhibit high matrilineal diversity, with unique haplogroups in the latter indicating exogenous animals. The preferred use of male mounts in army service mentioned in historical writings is confirmed. The absence of donkey jacks in our study area and the lack of mule matrilineal lineages unique to Late Iron Age horses contradict local hybrid breeding. Alleles associated with speed, endurance, or rare coat colors have not been identified, nor has a genetic basis for the larger body size of Roman horses, although illustrated by archaeozoological and historical data.