How Did Siamese Cats Originate?

With their characters and pattern of colouring, Siamese cats are an oddball.  Other breeds of cats might have distinctive colouring or shapes, but almost no other breed has 'points' like Siamese (Birmans are similar, but are probably also closely related).  Moreover, blue eyes are also generally rare in cats.

Siamese cats evince partial albinism.  This breed has a mutation in tyrosinaise -- an enzyme involved with production of melanin -- the chemical in skin or hair that gives it colour.  In Siamese cats, tyrosinase becomes heat sensitive, and only works in the cooler parts of the body: the face, limbs and tail.  This leads to Siamese cats having 'points'; places on their bodies which are non-white.

It's generally believed that Siamese cats first arose in SouthEast Asia.  They were especially liked and bred selectively in Siam (hence the breed's name).  The oldest illustrations of the breed (from the 1700s) show it with yellow eyes; so it's even more unclear when the blue-eyed cats arose.  Most Siamese cats in the West today are pretty closely related though, having descended from a small pool of animals imported into Britain in the early 1900s.