Traversing the ancient Overland Silk Road: Insights from domestic camel paleogenomics in Xi'an, China

The ancient Overland Silk Road connected distant regions through commerce and movement, enabling large-scale dispersal of domesticated animals alongside goods. However, the evolutionary and demographic trajectories of domestic camels, vital transport animals within this trade network, remain poorly understood due to a scarcity of paleogenomic data. In the present study, complete mitochondrial genomes (mitogenomes) and low-coverage nuclear genomes were obtained from three Camelus specimens excavated in Xi'an, a major eastern hub of the ancient Overland Silk Road, with calibrated radiocarbon ages of approximately 2 300-2 000, 900-700, and 300-0 years before present (cal BP). Phylogenetic analyses identified two individuals as domestic Bactrian camels and one individual as an Arabian camel, yielding the first genetically validated Arabian camel bone remain reported from China. Maternal haplotypes showed limited phylogeographic partitioning, consistent with extensive human-mediated dispersal. Notably, admixture analysis provided potential evidence of ancient interspecific hybridization, with 7.3% Arabian-related ancestry detected in the ~2 300-2 000 cal BP domestic Bactrian camel and 45.1% domestic Bactrian-related ancestry in the ~900-700 cal BP Arabian camel. This bidirectional introgression pattern suggests intentional breeding and circulation of hybrid camels for trade caravans. Overall, these findings support a model in which the ancient Overland Silk Road acted as a genetic corridor, repeatedly reshaping the demographic history of domestic camels through sustained mobility and recurrent admixture.