Unexpected occurrence of the western hoolock gibbon (Hoolock hoolock) in southwestern China suggests human-mediated translocation along the Southwestern Silk Road

Human activities have reshaped the distributions of animals for thousands of years, yet historical movements of wild species across biogeographic barriers often remain undetected. We investigated two hoolock gibbon specimens collected in 1960 from Datang, Tengchong, southwestern China, within the recognized range of Hoolock tianxing but far outside the known range of H. hoolock . We evaluated their taxonomic identity and geographic origin using curatorial records, deep-learning-based identification of upper-molar images, pelage morphology, mitochondrial phylogenetics, and genome-wide autosomal SNP analyses. The dental model assigned the available upper molar of the skull specimen to H. hoolock , and the pelage of the skin specimen was also consistent with this identification. Genomic analyses placed both specimens within H. hoolock , whereas mitochondrial data associated them with the southern mitochondrial lineage from central and southern Assam, northeastern India. Genome-wide analyses detected no substantial excess allele sharing with geographically adjacent H. tianxing , and both specimens showed relatively high heterozygosity, providing little support for an origin in a long-isolated natural population in western Yunnan. The occurrence of these specimens in Tengchong is therefore best explained by historical human-mediated translocation. The Southwestern Silk Road provides a plausible transport corridor, although the exact time of translocation remains unresolved. This study demonstrates how museum collections, genomics, and deep-learning-based identification can reveal undocumented human-driven changes in animal distributions.