The sinkhole in the Aucilla River, south of Tallahassee, in Florida, has been known by archaeologists for years. However, it is so dark that no divers would want to explore and examine it. But Jessi Halligan, a Florida State University professor, decided to conduct some research. The diving expeditions found mastodon tusks that had long grooves left by human tools. The discovery implies that humans inhabited the Florida area much earlier than had been thought initially thought, which dates back as far as 14,500 years ago.