Why do some cats have long hair and others have short hair?

The length of a cat's hair is primarily determined by their genetics. Specific genes in the cat's DNA control whether it has short or long hair.

The gene for fur length in cats is what scientists call an "incomplete dominant gene". That means when a cat inherits the long hair gene from one parent and the short hair gene from the other parent, the resulting offspring typically have a medium-length coat (like that of a Maine Coon).

The variation in hair length across different cat breeds is a result of selective breeding by humans over many generations. Some breeds, like the Persian, are known for their long, luxurious coats, while others, like the Siamese, have very short hair. Selective breeding for certain traits, including coat length, allows these distinct characteristics to become common within a particular breed.