How are hooves related to human fingernails and mammal claws?

Hooves, human fingernails, and mammal claws are all evolutionary variations of the same structure: hardened, keratinized outgrowths of the epidermis located at the tips of digits. They share a common origin and are composed of the fibrous protein keratin, which provides structural protection.1234

While they share this biological foundation, they differ in form and function:

• Claws: These are narrow, arched structures found in many mammals, birds, and reptiles. They are typically adapted for digging, climbing, or grasping prey.15
• Nails: Found in primates, these are broad, flattened plates. They represent an adaptation that facilitates fine motor skills and the manipulation of small objects rather than digging or defense.167
• Hooves: Characteristic of ungulates, hooves are essentially exaggerated, thickened nails that surround the end of the digit. They provide a durable, insensitive surface for bearing weight and are specialized for running.125

In all three cases, these structures grow continuously from a base and are worn down through daily activity.268