Nestled on Great Abaco Island in The Bahamas, Sawmill Sink a mysterious blue hole has revealed an extraordinary trove of fossils that shed light on the island’s ancient history. For over a decade, beginning in 2005, researchers plunged into the perilous depths of this natural wonder, uncovering secrets from a world long vanished.
“This was probably the most important site I’d ever had a chance to get involved with,” said David Steadman, curator emeritus at the Florida Museum of Natural History.
However, these groundbreaking explorations came to a halt five years ago when a devastating hurricane wreaked havoc on Great Abaco, disrupting the fossil collection efforts and leaving the remaining treasures submerged, possibly forever.
Formation of Sawmill Sink
Sawmill Sink, like other blue holes in The Bahamas, was formed when rising sea levels flooded limestone sinkholes after the last Ice Age. Thousands of years ago, Great Abaco was ten times larger than it is today. As the oceans rose, the island’s porous limestone foundation collapsed, creating a network of underwater caves and sinkholes.
Descending 150 feet below sea level, Sawmill Sink is a treacherous labyrinth of dark water and narrow crevices. Layers of freshwater, a toxic hydrogen sulfide mix, and oxygen-deprived saltwater make the site dangerous but perfect for fossil preservation.
Fossils Frozen in Time
In 2005, diver Brian Kakuk spotted the first of many fossilized treasures a wealth of bones offering a glimpse into the island’s prehistoric biodiversity. These included the remains of tortoises, crocodiles, and bird species no longer found on Great Abaco.
One of the first discoveries, a tortoise species later named Chelonoidis alburyorum, turned out to be entirely new to science. Its well-preserved remains hinted at a time when Abaco’s ecosystem thrived with diverse wildlife.
The fossils also revealed that many species met their demise in Sawmill Sink’s vertical trap, unable to climb out once they fell in.
Fossil evidence shows that 15,000 years ago, Sawmill Sink was a dry cave teeming with life, including roosting barn owls, crocodiles, and a variety of mammals and birds. The site’s unique preservation conditions allowed researchers to trace how these species adapted or failed to adapt to shifting climates during the Ice Age.
Yet, the arrival of humans around 1,000 years ago proved even more catastrophic for Abaco’s fauna.
The Impact of Humans
The Lucayan people, part of the Taíno culture, likely arrived on Great Abaco around 720 CE. Fossils indicate they hunted large tortoises and rodents like the hutia, both of which disappeared soon after their arrival.
Even non-prey species suffered. Birds like the Bahaman caracara went extinct due to competition for resources, while habitat destruction led to the decline of bats. Crocodiles, including the aggressive and intelligent Cuban crocodile, may have also been hunted by humans, who sought to eliminate a rival predator.
A Legacy Preserved
Before the hurricane interrupted their work, researchers had collected thousands of fossils from Sawmill Sink, which now reside in a new natural history museum. These discoveries offer invaluable insights into how climate change and human activity shaped the fate of Great Abaco’s wildlife.
Though many fossils remain submerged in the blue hole’s depths, Sawmill Sink continues to be a reminder of a vibrant past and a cautionary tale of environmental change.