Geologists investigated a submerged 25-foot bridge to address a long-standing archaeological debate: When did humans first settle on the islands in the western Mediterranean? Their findings help to bridge the historical gap in settlement timelines between the eastern and western parts of the Mediterranean.
A recent study led by the University of South Florida has illuminated the timeline of human colonization in the western Mediterranean, indicating that people arrived there earlier than previously thought. This research, published in the journal Communications Earth & Environment, challenges established beliefs and aligns the settlement dates of the Mediterranean islands more closely.
Reconstructing the early human settlement history of Mediterranean islands faces hurdles due to scarce archaeological evidence. By examining the 25-foot submerged bridge, a team of researchers led by USF geology Professor Bogdan Onac gathered significant evidence of earlier human activity within Genovesa Cave, located on the Spanish island of Mallorca.
“The submerged bridge and other artifacts suggest a high level of activity, indicating that early settlers recognized the cave’s water resources and strategically constructed infrastructure to navigate them,” Onac remarked.
This cave, situated near the coast of Mallorca, now contains flooded passages due to rising sea levels, with unique calcite deposits created during times of elevated sea levels. These deposits, along with a lighter mineral band on the submerged bridge, act as indicators for accurately tracking past sea-level fluctuations and determining when the bridge was built.
Although Mallorca is the sixth largest island in the Mediterranean, it was one of the last to be settled. Previous studies had suggested human activity on the island for up to 9,000 years, but inconsistencies and inadequate preservation of radiocarbon-dated materials like nearby bones and pottery raised doubts about these claims. More recent investigations have used charcoal, ash, and bones found on the island to estimate a timeline for human settlement around 4,400 years ago. This timeframe coincides with significant environmental changes, including the extinction of the goat-antelope species Myotragus balearicus.
By examining the mineral overgrowths on the bridge and the height of a colored band on it, Onac and his team determined that the bridge was actually constructed close to 6,000 years ago, which is over 2,000 years earlier than previously thought—thereby narrowing the settlement timeline gap between the eastern and western Mediterranean regions.
“This research highlights the value of interdisciplinary teamwork in revealing historical insights and enhancing our understanding of human history,” Onac stated.
This study received support from multiple National Science Foundation grants and involved extensive fieldwork, including underwater research and accurate dating methods. Onac plans to keep investigating cave systems, some of which have formed deposits dating back millions of years, to better understand preindustrial sea levels and assess the effects of contemporary greenhouse-induced sea-level rise.
This research was conducted in partnership with Harvard University, the University of New Mexico, and the University of Balearic Islands.
