Investigations of a French cave suggest Neanderthals were more industrious than previously thought.

Scientists say they have found evidence that Neanderthals were building complex underground structures, possibly used for rituals, 176,500 years ago.

New research published in the journal Nature describes fragments of stalagmite inside Bruniquel Cave in south-west France being snapped from the cave floor stacked into structures.

Our ancient ancestors formed circular walls, some up to knee-high, in a set of six distinct structures around 300 metres inside the cave.

The site has been dated to period tens of thousands of years before the first Homo sapiens arrived in Europe.

It also pushed back the dating of the first-known cave exploration by our human predecessors by tens of thousands of years, and is among the oldest-known human constructions.

Neanderthals appear to have broken the 2 tonnes of stalagmite pillars into about 400 pieces to mark out a total length of 112.4 metres.

The scale of the project implies the ability to work as a group. The fact that traces of fire and burnt pieces of bone were found at the same site suggests it was used for something, possibly ritualistic.

“Neanderthals were inventive, creative, subtle and complex,” study co-author Professor Jacques Jaubert of Bordeaux University said.

“They were not mere brutes focused on chipping away at flint tools or killing bison for food.”

“Early Neanderthals were the only human population living in Europe during this period,” the multinational team of authors wrote.

“Our findings suggest that their society included elements of modernity, which can now be proven to have emerged earlier than previously thought.”

We are constantly learning how similar Neanderthals were to us – the modern Homo sapiens.

Because the disappearance of Neanderthals roughly overlaps with the spread of Homo sapiens out of Africa and into Europe, it was long suspected they disappeared because we outsmarted them.

But Neanderthals were far from stupid.

We know that they were making cave etchings some 40,000 years ago, and appear to have been the first to catch, butcher and cook wild pigeons.

They also ate salad, cared for their elderly, buried their dead, travelled in boats and possibly even made the first jewellery.

We now know that we inter-bred with them as well. 

“The Neanderthal group responsible for these constructions had a level of social organisation that was more complex than previously thought,” the new study states.

“We could assume” there was some kind of symbolic or ritual use, the authors said, but they may have had more “domestic” purposes or even be used as a refuge.

“What surprises us most is the ability of Neanderthals to have explored very deep into caves … far from natural light,” Professor Jaubert said.

“We believe we are providing evidence of the capacity of Neanderthals to enter a hostile, underground environment, using fire to light the way, to do things that go beyond mere survival.”

Archaeologist Marie Soressi of the University of Leiden – who was not involved in the study - agreed that it must have been Neanderthals that built the structures.

“We don't have any other type of humans in Europe at that time,” she said.

“It's clearly too big to be a structure made by cave bears which are known to hibernate deep inside caves. It is also completely unknown for cave bears to pile up fragments.”