What a submerged ancient bridge discovered in a Spanish cave reveals about early human settlements

A new study from the University of South Florida has shed light on human colonization of the western Mediterranean, revealing that humans settled there much earlier than previously thought. The research, detailed in a recent issue of the journal, Earth & Environment Communications, challenges long-held assumptions and narrows the gap between island settlement chronologies across the Mediterranean region.

Reconstructing early human settlers on Mediterranean islands is challenging due to a lack of archaeological evidence. By studying a 25-foot submerged bridge, an interdisciplinary research team led by USF geology professor Bogdan Onac was able to provide compelling evidence of early human activity in Genovesa Cave, located on the Spanish island of Mallorca.

“The presence of this submerged bridge and other artifacts indicates a sophisticated level of activity, implying that early settlers recognized the cave’s water resources and strategically built infrastructure to navigate it,” Onac said.

The cave, located near the coast of Mallorca, features passages that are now flooded due to rising sea levels, with distinct calcite encrustations forming during periods of high sea levels. These formations, along with a light-colored band on the submerged bridge, serve as proxies to accurately track historical sea-level changes and date the bridge’s construction.

Mallorca, despite being the sixth largest island in the Mediterranean, was one of the last to be settled. Previous research suggested human presence dating back 9,000 years, but inconsistencies and poor preservation of radiocarbon-dated material, such as nearby bones and pottery, have led to doubts about these findings.

More recent studies have used charcoal, ash, and bones found on the island to create a timeline of human presence about 4,400 years ago. This aligns the timeline of human presence with important environmental events, such as the extinction of the genus Myotragus balearicus, a species of goat-antelope.

By analyzing mineral blooms on the bridge and the elevation of a band of coloration on the bridge, Onac and the team discovered that the bridge was built nearly 6,000 years ago, more than two thousand years older than the previous estimate, narrowing the time gap between eastern and western Mediterranean settlements.

“This research underscores the importance of interdisciplinary collaboration to uncover historical truths and advance our understanding of human history,” Onac said.