Why did horses disappear from North and South America near the end of the Pleistocene?

The disappearance of horses (Equus) from North and South America near the end of the Pleistocene Epoch (approximately 10,000 to 8,000 years ago) remains a subject of scientific uncertainty. While horses had flourished in their North American homeland throughout the Pleistocene, their sudden extinction in the New World is not fully understood.12

Several hypotheses have been proposed to explain this event, though none are definitive:

• Human Impact: The "prehistoric overkill hypothesis" suggests that human populations arriving in the Americas hunted horses to extinction. However, this theory faces significant objections, including a lack of clear archaeological evidence linking human hunters to the decline and the fact that other large species survived.31
• Environmental and Climatic Factors: Changes in habitat, direct climatic effects, and shifts in the intensity of seasonal conditions are considered likely contributors. For example, the expansion of dry shortgrass prairies may have placed grazing horses at a competitive disadvantage compared to other species like bison.3
• Disease: Some scholars have suggested that the emergence of devastating diseases may have played a role in the demise of the genus in the New World.1

Ultimately, the exact cause remains uncertain, and the subsequent submergence of the Bering land bridge prevented any natural return migration of horses from Asia until they were reintroduced by Spanish explorers in the 16th century.1