The first horses
Eohippus is the size of a fox, has four toes in front, and eats leaves in the forest.
- When
- —
- Duration
- 5 million years
- Known to
- ± 1 million years
- Era
- Eocene, Cenozoic
The earliest horses appear right at the start of the Eocene, small browsing animals with padded, multi-toed feet suited to soft forest floors and low-crowned teeth for leaves. The horse lineage became the textbook example of evolution largely because its North American record is so continuous — but the textbook version, a straight march from small to large and many toes to one, is wrong. The real pattern is a branching bush with many side lineages, most of which went extinct, and size that went down as often as up.