A Submerged Bridge Has Helped Solve of the Mediterranean's Great Mysteries, Shedding Light on When Humans Arrived

A few years ago, in 1999, researchers from the University of the Balearic Islands (UIB) discovered something surprising while studying caves in Manacor, Spain. They found a small megalithic bridge about 26 feet long, a now-submerged structure built thousands of years ago with large blocks of limestone to cross a lake between two chambers. The discovery was fascinating, but scientists haven't understood how relevant it was to the history of Mallorca and the Mediterranean until now—almost a quarter of a century later.

The discovery sheds light on the chronology of the island and its first settlements, with all that this implies for the history of the Mediterranean.

A bridge for history. The study’s protagonist, a small 25-foot megalithic construction, has attracted the attention of archaeologists dedicated to the analysis of the Mediterranean.

Blocks of limestone, up to 4.2 feet wide in some sections, were stacked to form the structure. Researchers believe that thousands of years ago, the first settlers used it to cross a lake and move between two elevated chambers of the Genovesa cave in Manacor. The researchers also believe construction may have begun when the lake was almost a foot deep. However, given that the water rose over time, the bridge is now submerged.

Surprises. This small structure has stoked interest on both sides of the Atlantic. It could help us learn more about the colonization of Mallorca and, by extension, the western Mediterranean.

According to CNN, a few years after the find, a study concluded that the bridge was about 3,500 years old. Researchers estimated the date based on ceramic remains found in a cave chamber. Experts from Harvard, New Mexico, South Florida, and the Balearic Islands have recalculated and extended that age. In a recent article published in Communications Earth & Environment, they argue that the bridge is at least 5,600 years old.

How did they calculate it? By studying the bridge and its surroundings. The cave has some flooded passages, but the researchers observed calcite incrustations formed by the sea. To be precise, they noticed that the bridge had a relevant detail: a curious bright mark on the upper part, which led them to believe that it could reveal calcite formation at the height where the water reached in the past. They refined the calculation with this data, the height of the structure, and a model of sea levels during the upper Holocene.

“We saw that the rise in sea level during the Holocene coincided with the location of the bridge, so we decided to do a sampling to relate the oscillation of the sea level with the depth of the bridge,” Joan Fornós, a lecturer at UIB and one of the authors of the study, told EFE.

“Due to radiometric dating, we saw that there was a stabilization of the sea level between 6,000 and 5,600 years ago that coincided with the white mark observed on the bridge. It is unlikely that the bridge would have been built more than 6,000 years ago because the area it covers would not have been underwater according to our model,” he added.

The value of a number. The study allowed the researchers to calculate that the bridge is almost 6,000 years old, an estimate that extends the previous calculation by more than 2,000 years. Experts from the University of South Florida (USF) pointed out the data is relevant not only because it allows us to learn more about a small viaduct hidden in the Balearic Islands.

In fact, this find is fascinating because it sheds light on the history of Mallorca and part of the Mediterranean. It provides information to answer a fundamental question: When did the first human settlements appear on the Balearic Islands? This question isn’t insignificant. Mallorca is the sixth-largest island in the Mediterranean. Still, experts believe it was one of the last to be colonized.

Revising the calendar. Some researchers have already suggested that the presence of humans in Mallorca could date back to 9,000 years ago. Still, the USF notes that this estimate has “inconsistencies and [includes] poor preservation of radiocarbon-dated material,” such as bones and ceramics.

Other recent studies have relied on charcoal, ash, and bone remains found on the island to establish a chronology of human occupation dating back 4,400 years. What we now know about the Genovesa cave bridge, an infrastructure built by humans at least 5,600 years ago, allows us to extend that timeline by more than a millennium.

A challenge for history. “Reconstructing early human colonization of the Balearic Islands in the western Mediterranean is challenging due to limited archaeological evidence. Current understanding places human arrival ~4400 years ago,” the experts said in their study.

“Subsequent sea-level rise flooded the archeological structure, ruling out later construction dates. This provides evidence for early human presence on the island dating at least 5600 and possibly beyond ~6000 years ago,” they added.

Beyond the Balearic Islands. “It is clear that humans were there a thousand years earlier than previously thought and that there could have been a potential human presence on the island for around 9,000 years,” Fornós told EFE.

The USF gives an even greater dimension to the finding, claiming that the study “sheds light” on the human colonization of the western Mediterranean, “revealing that humans settled there much earlier than previously believed. This research challenges long-held assumptions and narrows the gap between the settlement timelines of islands throughout the Mediterranean region,” they point out. The last nuance isn’t insignificant. The authors insist that the Manacor bridge has narrowed “the gap between the settlement timelines of islands throughout the Mediterranean region.”

Image | University of South Florida (M.À. Perelló)

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