Circular heated structures built by Neanderthals have been discovered deep inside a cave in France and are now among the world's oldest known human-made constructions, a new study has found.
The structures, dated to around 176,000 years ago and described in the journal Nature, provide evidence that Neanderthals were clever about using fire, had complex spatial organizational abilities, and explored at least one extensive cave system. They additionally indicate that humans began occupying caves much earlier than previously thought; until now the oldest formally proven cave use dated back only 38,000 years (Chauvet).
The site where the constructions were found -- Bruniquel Cave in southwestern France -- was only just discovered in 1990 by scientist and spelunker François Rouzaud.
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"Bruniquel Cave's entry had collapsed, such that it remained untouched for millennia," project leader Jacques Jaubert, a professor of prehistory at the University of Bordeaux, told Discovery News, explaining why the cave took so long to find.
Rouzaud had hoped to investigate Bruniquel Cave further, but he died in 1999 while exploring another French cave, Foissac in Aveyron. Access to Bruniquel was restricted after its 1990 discovery until 2013, when the new research began.
While investigating the cave, Jaubert and his team found that it includes at least six structures built by Neanderthals using nearly 400 stalagmites and stalagmite fragments. The paper focuses on two of the constructions that are circular-shaped and large, with one being 22 feet wide and the other just over 7 feet wide.
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The stalagmites were stacked in layers to form ringed "walls." The materials were red, black and cracked in places, providing evidence for hearth fires that the researchers believe were built above ground, rather than directly on the cave floor. A burnt bear bone, along with bits of char, was also found.
Jaubert and his team wrote: "Based on most Upper Paleolithic cave incursions, we could assume that they represent some kind of symbolic or ritualistic behavior, but could they rather have served for an unknown domestic use or simply as a refuge? Future research will try to answer these questions."
Given the depth and darkness of the cave, Jaubert said it is at least clear that Neanderthals were controlling fire for lighting, in addition to using it for heating and possibly other purposes.
Drilling into the stalagmitic floor inside one of the structures in the Bruniquel Cave.
The researchers conclude that modern humans did not build the structures since there is no evidence for Homo sapiens in the region at the time they were constructed. Neanderthals, on the other hand, were known to be in Europe and Asia then.
The scientists suspect that the Neanderthals at Bruniquel Cave left behind tools and possibly other items, but Jaubert said that such likely objects would have been "covered with thick calcite, leaving them frozen for eternity." Time will tell if future excavations within the cave can recover additional artifacts.
Marie Soressi, an archaeologist at Leiden University, wrote a separate "News & Views" piece, also published in Nature, about the discoveries.
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Soressi believes that the newly found structures "are the oldest directly dated constructions attributed to Neanderthals, and the first ones for which we can be confident of that attribution."
She added, "Only further discovery of underground structures will help to establish whether these structures were opportunistic ones relating to an accidental underground visit, or whether they were part of regular and planned Neanderthal activities."
Soressi suspects that greater evidence for Neanderthal culture could be lacking simply due to poor preservation. If it were not for a fortuitous series of events, including the natural closure of Bruniquel Cave's entrance for thousands of years, the Neanderthal-built structures would not have been preserved.
Jaubert thinks that the new research, along with other recent finds, is blurring the line between Homo sapiens and Neanderthals.
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"The differences are being erased," he said. "We now believe that Neanderthals in Europe and modern humans in Africa had very close, if not interchangeable, technical abilities, social capacities, symbolic ways of life and more."