An ancient submerged bridge discovered in a cave on Spain’s Mallorca island is providing valuable insights into early human settlement patterns across the western Mediterranean. New research reveals that humans may have inhabited Mallorca much earlier than previously thought, potentially bridging the gap between eastern and western Mediterranean colonization.
Published in *Communications Earth & Environment*, the study focuses on a 25-foot-long (7.6-meter-long) bridge located within Genovesa Cave. The research suggests that human presence on Mallorca dates back significantly further than earlier estimates. This could offer a clearer picture of how and when humans dispersed across the Mediterranean.
Historically, determining the timeline for human settlement on Mediterranean islands has been challenging due to a lack of written records and scarce archaeological evidence. However, the submerged bridge’s “bathtub ring” and associated mineral deposits have enabled scientists to estimate its construction to be around 6,000 years ago, according to Bogdan Onac, the lead author of the study and a professor at the University of South Florida’s School of Geosciences.
“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 explained.
The bridge is constructed from large limestone blocks, with some spanning 4.2 feet (1.3 meters). The exact methods used by ancient humans to construct this bridge remain unknown. Researchers speculate that the bridge was intended to provide a continuous, dry pathway connecting the cave’s entrance to a chamber beyond an internal lake.
The bridge was first discovered in 2000. Early estimates in a Catalan-language study placed its age at around 3,500 years, based on pottery found in the cave. However, subsequent research, including radiocarbon dating of bones and pottery on Mallorca, suggested a human presence on the island as far back as 9,000 years. Due to the poor preservation of these materials, this timeline has been questioned.
Recent studies analyzing ash, bones, and charcoal on the island have proposed a settlement date of approximately 4,440 years ago. Yet, Onac and his team opted for a different approach. They examined the rise of sea levels and the geological markers it leaves behind.
“It was only in the past four years that we finally gathered the data needed to address this longstanding research topic and better estimate the arrival time of humans in Mallorca,” Onac noted.
Today, rising global sea levels have flooded the passages of Genovesa Cave. Onac and his team investigated a light-colored band on the submerged bridge and calcite encrustations formed during higher sea levels. Speleothems, which are mineral deposits in caves, provided crucial data.
By reconstructing historical local sea levels and analyzing the bridge’s color band and mineral deposits, the researchers determined that the bridge was likely built around 6,000 years ago. The color band aligned with the level where mineral deposits formed when the sea level was stable, suggesting construction occurred before 5,600 years ago.
Onac also noted that the bridge was probably used for 400 to 500 years before rising sea levels submerged it. While there is no definitive evidence on how ancient humans utilized the cave, a few possibilities are being considered.
Fossil remains of the extinct goat species Myotragus balearicus and pottery found in a chamber linked to the cave entrance by the bridge hint at potential uses of the cave. “This suggests that humans may have used the area near the cave entrance, a large collapse chamber, for living,” Onac suggested. “The purpose of crossing the lake to access that chamber remains unclear; it could have served as a refuge, place for rituals, or as a storage place, keeping food out of Mallorca’s hot days.”
Archaeological evidence shows small stone homes and large stone structures on Mallorca from 2,000 to 4,500 years ago, suggesting that the cave bridge might represent an early stage in the development of more advanced stone constructions on the island.
Paleontologists are still exploring why Mallorca was settled later than other Mediterranean islands. Despite its proximity to Spain’s mainland, Mallorca’s hot, dry climate and thin soil for farming, coupled with limited natural resources aside from fish and native goats, might have made it less appealing. “In contrast, other islands had more favorable environmental conditions and abundant resources, such as minerals and livestock, which made them more attractive for early settlers,” Onac concluded.
