Close-up view of the submerged stone bridge (left) from Genovesa Cave in Mallorca, Spain. Stone path (right) connecting the entrance of the cave and its subterranean lake, across which the bridge was constructed.

Close-up view of the submerged stone bridge (left) from Genovesa Cave in Mallorca, Spain. Stone path (right) connecting the entrance of the cave and its subterranean lake, across which the bridge was constructed. | UIB

Humphrey CarterPalma31/08/2024 11:19
TW
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The dating of a submerged bridge in the Genovesa cave in Manacor to at least 5,600 years ago (BC) indicates that humans arrived in Mallorca at least 1,000 years earlier than previously thought, according to a study published in Communications Earth & Environment. Researchers from the University of the Balearic Islands (UIB) discovered this submerged megalithic bridge in 1999 while studying the topography of the caves in the area, one of the authors, Joan Fornós, a scientist in the UIB’s Department of Earth Sciences, said.

The bridge, once used to cross an existing lake in the area, consists of large limestone blocks placed one on top of the other to connect two elevated chambers of the Genovesa cave in Manacor so that humans could pass from one to the other “dry”. The UIB researchers found that the bridge had a striking mark of different colouring on its upper section, which would indicate the formation of calcite at the point where the water level reached when the bridge was still in use.

They then compared the height of the bridge and the height of the colouring mark with a model of relative sea levels in this area of Mallorca 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,” says Fornós.

“Thanks to radiometric dating, we saw that there was a stabilisation of the sea level between 6,000 and 5,600 years ago that coincided with the white mark observed on the bridge,” he adds. The mark cannot be more recent, he says, because stalactites have been found underneath. “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 under water according to our model,“ says Fornós.

The finding is the result of close collaboration with scientists from the US universities of South Florida and New Mexico (on radiometric dating) and Harvard (on modelling Holocene sea levels). Previous research suggested a time period for the first settlement on Mallorca of between 4,600 and 4,200 years ago. Mallorca was one of the last islands to be colonised by humans in the Mediterranean, “it is clear that man was there a thousand years earlier than previously estimated, and that there may have been a potential human presence on the island from approximately 9,000 years ago,” concludes Fornós.