Ancient Underwater Stone Bridge Unveiled: 5,600-Year-Old Structure Redefines Human History
Experts from the University of South Florida unearthed a 5600-year-old underwater stone bridge in an ancient cave on Mollurca island, Interesting Engineering reported.
The analysis conducted by the experts on the 25-foot-long (7.6-meter-long) bridge found inside Genovesa Cave has been published in the journal Communications Earth & Environment.
The study showcases how human settlement might have been a reality on many of these islands across the western Mediterranean Sea way earlier than previously hypothesized by scientists.
Current understanding places the time of human arrival on these islands 4,400 years ago. But, tests on the bridge have revealed it to have been formed around 5,600 years ago, which provides evidence for early human presence on the island during that period.
The bridge was first discovered in 2000, CNN reported. A previous study estimated the bridge to be 3,500 years old, based on pottery found in one of the cave’s chambers. Another research estimated human presence on the island to be at least 9,000 years old. Several experts have argued against this assertion, citing poor preservation of the materials in the cave.
Natural processes in recent times allowed scientists to analyze the newly surfaced geological footprints that were previously hidden beneath waters and rubbles.
"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," lead study author Bogdan Onac, a professor in the School of Geosciences at the University of South Florida said.
The team from the University of South Florida analyzed a light-colored band on the submerged bridge within the cave, and calcite encrustations that were on the bridge when the sea level was higher, CNN reported. The reconstruction of historic local sea levels, and tests on the coloration band on the bridge as well as the mineral deposits, made the scientists conclude that the bridge was put into place 6,000 years ago.
The color band matched the level where mineral deposits formed when the sea level was at a standstill, implying that the bridge must have been constructed earlier than 5,600 years ago.
The experts for their analysis also focussed on a telltale "bathtub ring," along with mineral formations found on the bridge. Tests on these items helped the experts understand the approach taken by humans in building the bridge.
"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, CNN reported.
The bridge was created out of large, heavy limestone blocks some of which are 4.2 feet (1.3 meters) in size. Experts have still not been able to identify the processes humans employed to build the bridge. They believe that the builders wanted the bridge to dry, and have a continuous path connected to the cave’s entrance with a chamber beyond a lake within the cave.
The findings also imply that the time difference between humans arriving in the eastern and western Mediterranean regions is much narrower than previously assumed by archeologists, CNN reported. Researchers are trying to understand how humans used the caves in those times.