Horse

The horse (Equus caballus) was domesticated on the steppes of western Eurasia roughly 4,000 to 4,500 years ago and transformed transport, farming and warfare. Its fossil record, from a small many-toed forest animal to today's single-toed runner, is a classic story in evolution.

🧬 Field Guide Specimen: Open Horse in the CRV Science Field Guide to log the specimen, see its place among the Mammals lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.

Early horses such as Eohippus (Hyracotherium) from about 55 million years ago were dog-sized with several toes. Over time the family diversified into many forms, with changes in tooth shape for grazing grass and in limbs for running on a single toe. Evolution was branching, not a straight ladder.

Genomic analysis in 2021 traced modern domestic horses to a lineage from the Volga-Don region that spread rapidly across Eurasia after about 2200 BCE. The Przewalski's horse, long called the last wild horse, turned out to descend from horses first domesticated by the Botai culture in Kazakhstan.

A stay apparatus of ligaments and tendons lets horses stand and even doze without muscular effort. A large hindgut ferments grass, and the single hoof is a modified middle toe.

• Evolution — the horse fossil record
• Plains Zebra — a wild equid