Complex sentence: Shells, bones and artifacts found on the island indicate extensive use of it by the Tequesta, and there are indications of a large community on the island between 1,500 and 2,000 years ago.
Split into simpler sentences: Shells, bones and artifacts found on the island indicate extensive use of it by the Tequesta. A large community appeared to inhabit the island between 1,500 and 2,000 years ago.