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A drown , human being - constructed limestone nosepiece discover inside a cave on a Spanish island is much old than previously guess , pushing back the record of when humans inhabited the placement , a raw subject determine .
Researchers discovered the limestone bridge in 2000 during a scuba - diving expedition inside the flooded cave in Mallorca , a Mediterranean island turn up off the eastern shoring of Spain ’s mainland . At the time , researchers determine that the 25 - foot - foresighted ( 7.6 metre ) bridge , which consist of great limestone blocks stacked on top of each other , was built around 4,400 year ago , according to a study published Friday ( Aug. 30 ) in the journalCommunications Earth & Environment .
An underwater view of the limestone bridge located inside a submerged cave.
" This dating was based on pottery shard that were recover inside the cave , " lead authorBogdan Onac , a professor of geology at the University of South Florida , told Live Science . " But now we know that this [ date ] was wrong . "
In gain to the broken artifacts , the cave was littered with bones from a now - out butt - antelope know asMyotragus balearicus , according to astatementfrom the university .
However , when mass occupy the cave still remained unclear .
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Even though Mallorca is a large island , it was one of the last to be inhabited in the Mediterranean . In contrast , Cyprus and Crete are consider to be the earliest island in the area and were occupied at least 9,000 long time ago , according to a subject area in the journalScience .
To determine the honest engagement of the bridge ’s grammatical construction , researcher studied a " trenchant light - one-sided dance orchestra " — akin to a " bathtub ring " — running along the bridgework ’s upper portion , according to the study . The transformation in colouration show change in sea level , as well as the growing of calcite encrustations that formed on the bridge when the H2O rose .
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Upon analyzing the mineral deposits , which are also do it as speleothems , researchers specify that the bridge was construct around 6,000 years ago , pushing back the timeline of human presence on the island by 1,600 years .
" This testify that the sea level sit down there for a couple hundred years , allow the mark to happen , " Onac read . " The meter when the bridge deck was constructed also show that people were utilizing this cave much earlier than previously thought , shut the interruption between easterly and westerly Mediterranean small town . "
The researchers said further research is necessary to determine why Mallorca was sink after than other island in the region , but it could be because the island miss resource demand for survival , such as farmable land .
