An ancient underwater bridge in a cave on the Spanish island of Mallorca is helping researchers discover when humans first began settling the islands of the western Mediterranean thousands of years ago. A study detailing these findings was published Friday (30) in the journal Communications Earth & Environment.
A new analysis of the 7.6-meter-long bridge, located in Genoese Cave revealed that the humans inhabited Mallorca one of the largest islands in the Mediterranean, much earlier than previously believed. The findings could help close the gap between human occupation in the eastern and western Mediterranean.
The lack of written records and limited archaeological evidence make it difficult to understand when the Mediterranean islands were colonized.
However, a telltale clue, along with mineral formations detected on the bridge, allowed scientists to estimate that the structure was built almost 6,000 years ago according to Bogdan Onac, a professor in the University of South Florida’s School of Geosciences and lead author of the study.
“The presence of this submerged bridge and other artifacts indicates a sophisticated activity suggesting that early settlers recognized the cave’s water resources and strategically built infrastructure to navigate it,” Onac said.
Mysterious cave
The bridge is made up of large limestone blocks, some up to 1.3 meters wide, and it is still unclear what mechanisms allowed ancient humans to build this bridge.
Researchers believe the bridge builders wanted a dry, continuous path to connect the cave entrance with a chamber beyond a lake inside the cave.
The bridge was discovered in 2000. A few years later, a study in Catalan estimated its age at around 3,500 years, based on ceramics found in one of the cave’s chambers.
Since then, research that has radiocarbon dated bones and pottery has suggested that humans may have inhabited Mallorca as early as 9,000 years ago, but the poor preservation of the materials has led researchers to question that timeline.
More recent studies examining ash, bones and charcoal on the island suggest that the humans settled there about 4,440 years ago .
By studying sea level rise on other islands and the geological traces that rising seas leave behind, Onac and his colleagues took a different approach.
“It is only in the last four years that we have finally gathered the data needed to address this long-standing research question and better estimate the timing of human arrival in Mallorca,” Onac explained.
Today, the corridors of the Genovese Cave remain flooded due to the sea level rise .
Onac and his team studied a clear band over the underwater bridge in the cave, as well as calcite encrustations that formed over the bridge during periods when sea levels were higher and filled the cave.
These incrustations are speleothems, geological formations resulting from the accumulation of mineral deposits over time in caves.
By reconstructing local historical sea levels and analyzing the color banding on the bridge, as well as mineral deposits, the team determined that the bridge was assembled about 6,000 years ago.
The color band coincided with the level where mineral deposits formed when sea levels were stable, indicating that construction must have occurred before 5,600 years ago, Onac said.
Retracing ancient steps
The bridge was likely used for 400 to 500 years before rising sea levels covered the structure, Onac said. The team doesn’t yet have clear evidence of how ancient humans used the cave, but they have a few hypotheses.
Divers have found fossils of an extinct species of goat known as Myotragus balearicus who lived on the island. They also discovered pottery in a dry chamber connected to the cave entrance by the bridge, according to Onac.
“This suggests that humans may have used the area near the cave entrance, a large collapsed chamber, as a place of habitation,” Onac said. “The purpose of crossing the lake to access this chamber is not yet clear; it could have been a refuge, a place for rituals or a storage place, protecting food from the hot days of Mallorca.”
There is evidence of small houses and structures made of large stones on Mallorca dating back 2,000 to 4,500 years, so the cave bridge is likely a precursor to the larger, more sophisticated constructions found on the island, Onac said.
Paleontologists are still trying to understand why Mallorca was settled later than the islands of the eastern Mediterranean. Although it is large and relatively close to the Spanish mainland, the island had a hot, dry climate with poor soil for agriculture. In addition, except for fish and native goats, Mallorca lacked abundant natural resources.
“In contrast, other islands had more favorable environmental conditions and abundant resources, such as minerals and livestock, which made them more attractive to early settlers,” Onac concluded.
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This content was originally published in 6,000-year-old underwater bridge reveals human presence in Mallorca cave on the CNN Brasil website.
Source: CNN Brasil
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