In 1983, a diver exploring the Aucilla River in Jefferson County, Florida, came across a collection of large bones on the riverbed. The bones belonged to an extinct elephant. The discovery led scientists to a buried sinkhole that contained a well-preserved record of an ancient environment.

The site, known as Page-Ladson, was excavated by a team led by paleontologist S. David Webb and archaeologist James Dunbar. Over the following years, divers worked in near-zero visibility to recover materials from the sinkhole, which had been sealed by sediment for thousands of years.

The team found stone artifacts in the same layers as the remains of mastodons. Radiocarbon dating suggested the material was about 14,400 years old. This created a problem for the archaeological community, where the dominant model held that humans first arrived in the Americas around 13,000 years ago. Some researchers argued that the artifacts had been moved by water or that the dates were unreliable.

For almost two decades, the site received little further attention.

In 2012, a new team returned to Page-Ladson. Led by geoarchaeologist Michael Waters and underwater archaeologist Jessi Halligan, the team re-excavated the sinkhole using modern techniques. They collected 71 radiocarbon samples from materials that were unlikely to be contaminated, including twigs and seeds from the same layer as the stone tools.

The results placed the artifacts between 14,700 and 14,400 years old, confirming the original dates. The team also recovered six additional stone tools, including a biface knife fragment that showed signs of extensive use.

A paleontologist re-examined the original mastodon tusk and found cut marks consistent with human activity. The grooves indicated that someone had removed the tusk from the skull, likely to access the nutritious tissue inside the pulp cavity.

The findings were published in May 2016 in Science Advances.

The site also provided information about the fate of North American megafauna, such as mastodons. Analysis of fungal spores in sediment cores showed that large herbivores remained present at the site for nearly 2,000 years after the humans arrived. The spores declined sharply around 12,600 years ago, coinciding with the Younger Dryas, a period of abrupt cooling.

This evidence suggests that the extinction of megafauna was not simply a rapid result of human arrival. Other factors, such as climate change and habitat loss, likely played a role.

The sinkhole is now located about 11.5 kilometers from the coast, but at the time it was used, sea levels were much lower. The site was then far inland, in a landscape of dry savanna where sinkholes provided reliable sources of fresh water.

The people who used the site lived more than 14,000 years ago. They hunted mastodons and used stone tools. While they were not the first inhabitants of the Americas, the evidence at Page-Ladson shows that human presence in the region predates the Clovis culture by over a thousand years.