New fossil DNA research has fundamentally reshaped the understanding of equine evolution, revealing that the extinct Dalian horse from northeastern China acted as a crucial genetic bridge between North America and Eurasia.
For decades, the prevailing narrative held that horses were introduced to the Americas by European colonizers, particularly Spanish conquistadors, who presented Native Americans with an animal previously unknown in the New World. However, this latest genomic investigation completely overturns that traditional story.
Horses actually originated in North America millions of years ago, and they only reached Europe thanks to a surprising genetic intermediary in China.
The Dalian Horse's Role
The Dalian horse, once considered a localized peculiarity confined to northeastern China, carried a distinct American genetic signature that it transmitted to ancient horse populations in Siberia, according to researchers from the State Key Laboratory of Geomicrobiology and Environmental Changes.
This gene flow indicates that the bloodlines that later gave rise to modern European horses acquired their American roots through this Chinese crossroads.
"Dalian horses likely served as one route through which North American-related genetic ancestry entered Northeast Eurasian horse populations," the researchers wrote in the Proceedings of the Royal Society B: Biological Sciences.
A 50,000-Year Journey
Equids originated in North America during the early Eocene epoch. The genus Equus, which first emerged around 4 to 5 million years ago, is the only surviving lineage, encompassing all modern horses, asses, and zebras.
According to fossil records, Equus dispersed from North America into Eurasia via the Bering Land Bridge approximately 2.6 million years ago, subsequently undergoing extensive evolutionary diversification.
A 2025 study had already established that ancient horses repeatedly migrated between North America and Eurasia during the late Pleistocene era when sea levels dropped and a land bridge connected the two continents.
The new study analyzed 20 Dalian horse samples from the late Pleistocene, mostly unearthed from Qinggang county in Heilongjiang province and Harbin. Researchers recovered complete mitochondrial genomes and identified a "distinctive component" of Eastern Beringian ancestry, essentially American DNA, that was absent from other northeast Asian equids.
The researchers suggested that gene flow across the Bering Land Bridge continued until after 50,000 years ago, though it was "intermittent and geographically limited."
Geographic Range Expansion
First identified from fossils in the Gulongshan Cave in Dalian, the Dalian horse was believed to be confined to northeastern China during the late Pleistocene. The new study extends its range; two equid fossils from Yakutia in the Russian Far East fell within the Dalian horse's mitochondrial diversity range.
This suggests the Dalian horse's range extended "from northern China at least northwestward to southern Siberia and northeastward to Yakutia," the researchers said.
Why the Dalian Horse Vanished
Despite its role as a genetic conduit, the Dalian horse ultimately vanished. The researchers found that its extinction was not due to a lack of genetic diversity, but to its inability to adapt to a changing climate.
Stable isotope analysis revealed the Dalian horse was a specialist grazer. As the environment shifted roughly 40,000 years ago, becoming more humid, with dry grasslands replaced by peatlands and wetlands, its narrow diet left it unable to adapt.
For the Dalian horse, its large body size and "limited ecological plasticity" meant it could not survive the loss of its high-quality forage.
This extinction trajectory mirrors other vanished large herbivores of the era, such as North American horses and the giant camel.
