By Mark Spowart / Getty Images
The United States hosts more than 10.3 million horses—about 18 % of the world’s equine population—and boasts over a hundred registered breeds, making North America the most diverse equine region on Earth. Mexico follows with 6.4 million horses. Yet, despite this modern abundance, horses were once native to the continent and vanished around 10,000 years ago.
North America’s first equids appeared roughly 30–40 million years ago, evolving into the modern‑looking Equus scotti. These horses were widespread until the end of the Pleistocene, when a series of megafaunal extinctions swept the continent. While many large mammals—such as mammoths, mastodons, and saber‑toothed cats—disappeared, evidence shows that horses survived well into the Holocene.
A 2021 study published in Nature Communications analyzed ancient DNA from soils and found horse populations declining before the Pleistocene‑Holocene transition but still present 6,000 years ago. This challenges the view that horses went extinct during the late Pleistocene megafaunal crisis.
The retreat of the last ice age altered grasslands into tundra, reducing the grazing habitat horses depended on. Simultaneously, early human hunters—likely arriving around 13,000 years ago—began hunting horses for meat and resources. A 2001 discovery at the St. Mary Reservoir in Alberta revealed butchery marks on horse vertebrae, confirming prehistoric predation.
In 2015, researchers published a paper in the Proceedings of the National Academy of Sciences that radiocarbon‑dated seven horse and one camel skeletons to 13,300 years ago. The marks on the bones indicated systematic hunting, predating the previously assumed onset of human activity by about 300 years.
Beyond climate and hunting, competition for forage intensified as bison and other grazers expanded. Fossil evidence indicates a contraction of horse ranges and a gradual reduction in body size, signaling chronic food shortages. The combined effect of shrinking habitats, dietary stress, and human exploitation likely accelerated the decline.
While human hunting undoubtedly exacerbated the situation, many experts argue that environmental changes—particularly the loss of extensive grasslands—were the primary driver. The interplay of these factors underscores the complexity of megafaunal extinctions.
Before their extinction, horses had already migrated out of North America across the Bering Land Bridge, reaching Eurasia around one million years ago. The modern equines reintroduced by Spanish conquistadors in the 1400s were genetically distinct from the extinct Equus scotti but carried forward their evolutionary lineage. Today’s diverse horse breeds are a testament to that enduring heritage.
