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The exceptionally-rich fossil record available for the equid family has provided textbook examples of macroevolutionary changes. Horses, asses and zebras represent three extant subgenera of Equus lineage, while the Sussemionus subgenus is another remarkable Equus lineage ranging from North America to Ethiopia in the Pleistocene. We sequenced 26 archaeological specimens from northern China in the Holocene that could be assigned morphologically and genetically to Equus ovodovi, a species representative of Sussemionus. We present the first high-quality complete genome of the Sussemionus lineage, which was sequenced to 13.4× depth-of-coverage. Radiocarbon dating demonstrates that this lineage survived until ~3,500 years ago, despite continued demographic collapse during the Last Glacial Maximum and the great human expansion in East Asia. We also confirmed the Equus phylogenetic tree, and found that Sussemionus diverged from the ancestor of non-caballine equids ~2.3-2.7 Million years ago and possibly remained affected by secondary gene flow post-divergence. We found that the small genetic diversity, rather than enhanced inbreeding, limited the species' chances of survival. Our work adds to the growing literature illustrating how ancient DNA can inform on extinction dynamics and the long-term resilience of species surviving in cryptic population pockets.

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Cattle are one of the six livestock species that have occupied an important place in Chinese history. Previous ancient DNA studies have indicated that Chinese taurine cattle (Bos taurus taurus) are exotic, but the exact route and diffusion by which they were introduced to China is unknown. In this study, we extracted the mitochondrial genomes of 34 cases of ancient taurine cattle (from the late Neolithic to Qin and Han dynasties) excavated from sites in northern China and the eastern Eurasian steppe, and successfully obtained 14 mitochondrial genome sequences. The results of ancient DNA analysis reveal that with cultural exchange and trade, there was close genetic exchange between domestic taurine cattle in different regions. The haplotypes shared by domestic cattle have genetic continuity, reflecting the strong cultural influence of the large capital city sites such as Taosi, Shimao and Erlitou on the surrounding areas. This study suggests that ancient northern Chinese taurine cattle may have accompanied the westward transmission of agricultural or painted pottery culture and thus had a maternal genetic contribution to modern Tibetan cattle.