Horses in North America: Native, Extinct, Reintroduced

Horses originated in North America — then went extinct here, only to return with Europeans.

Evolutionary History

• 55 MYA: Eohippus (dawn horse) — dog-sized, forest browser
• Miocene/Pliocene: Diversification — Merychippus, Pliohippus, Equus (modern genus, ~4 MYA)
• Pleistocene (2.5 MYA – 10 KYA): Equus abundant across continent — multiple species

Extinction (~10,000 Years Ago)

Dual drivers:

1. Climate change: End of Ice Age → loss of steppe habitat, vegetation shift
2. Human hunting: Clovis/other Paleoindians — overkill hypothesis debated but supported by kill sites

All North American Equus species vanished. Survivors in Asia (via Beringia) gave rise to modern horses, donkeys, zebras.

Reintroduction (16th Century)

• 1519: Cortés lands 16 horses in Mexico
• 1540s: Coronado, de Soto expeditions bring horses north
• 1680: Pueblo Revolt → massive horse dispersal to Plains tribes
• 1700s: Horse culture transforms Plains Indigenous life (Comanche, Lakota, etc.)

Modern Wild Horses

Today's mustangs are feral descendants of Spanish/Iberian stock — not native wildlife in ecological terms, but culturally iconic. Managed under 1971 Wild Free-Roaming Horses and Burros Act.