The Calusa Indians were originally called the "Calos" which means "Fierce People." They were descendants of Paleo-Indians who inhabited Southwest Florida approximately 12,000 years ago. During the Calusa's reign the Florida coastline extended roughly 60 miles further into the Gulf of Mexico. Hardwood forests covered the land and the climate was much colder than it is today. The Calusa inhabited a region abundant with bears, woolly mammoths, sloth, tortoises, and saber-toothed tigers. Hunting these animals and gathering roots and fruit that grew on trees was a mainstay until they discovered the waters contained a wealth of fish. This new food source required significantly less time than hunting and gathering their food, and allowed the Calusa time to establish their own system of government. Following this formation of a centralized government were the construction of a canal system, the beginnings of organized religion, and the creating of many art forms.
[Excerpt from: Absolutely Florida Websource: The Calusa Indians (The Shell People.)]