Why do horses have teeth adapted for grinding vegetation?

Horses have teeth adapted for grinding vegetation because they are herbivores that evolved to consume grass, a coarse food source that causes significant wear on dental surfaces.12

To ensure they have an adequate grinding surface throughout their life span, horses possess specialized hypsodont (high-crowned) teeth. These teeth are structured as high prisms that continue to grow out of the jaw to replace the surfaces worn away during the grinding process.123

The evolution of these teeth was a critical adaptation that occurred as grasses became widespread across North American plains. The cheek teeth (premolars and molars) developed strong crests and became adapted to the side-to-side motion of the lower jaw necessary to grind grass blades. Furthermore, the hollows between the ridges of these teeth are filled with a deposit of secondary cement, which strengthens the structure and increases its resistance to wear. This specialized dentition allows the horse to efficiently process fibrous plant matter, which is essential for their survival.231