Why do some cats have extra fingers?

Some cats have extra fingers due to a genetic mutation known as polydactylism. This condition causes cats to develop more than the usual number of toes, often on their front paws but sometimes on their back paws as well. It's more common in certain breeds and was famously favored by writer Ernest Hemingway, leading to a population of polydactyl cats in his former home in Key West, Florida. While the extra toes can be charming, they generally do not affect the cat's health or mobility.