Leather? A polymer? That's right! Leather is made from animal skin, rawhide, as some call it.
Skin?! A polymer?! That's right! Animal skin, yours included, contains a strong network of the polymer collagen. Collagen belongs to the family of polymers called proteins.
Proteins are one of many naturally occurring polymers. They are also are a type of polyamide, and are, in fact, very similar to nylon.
Rawhide is made into leather by a process called tanning, in which the collagen in the rawhide is crosslinked to make it stronger, tougher, more flexible, more durable, and also to help keep it from rotting.
To give you an idea of just how much the process of tanning changes the polymers in the animal skins, look for rawhide chew toys for dogs in a pet store (or in the pet aisle of your grocery store). Compare that stiff, rough stuff to the leather used in shoes or purses. Pretty amazing, huh?!