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Credit: MARCO BERTORELLO via Getty Images
Archaeologists in the Iberian Peninsula have discovered a 65-year-old tar-making “factory” developed by Neanderthals – an activity taken 20,000 years before modern humans.Homo sapiens) footprint in society, a new study finds.
Glue tar helped Neanderthals make glue to make weapons and tools. The so-called factory – a well-designed environment – enabled the Neanderthals to precisely control fire and control the temperature of the flame that created their gooey creations.
Archaeologists already knew that Neanderthals developed glue, including tar and resin together with sticky substances from ocher, a reddish mineral It is often used in stone production. Neanderthals used these adhesives to fasten, or attach, stone blades or points to wooden handles, as well as sinew or plant fiber wrappings.
But a newly discovered furnace, which seems to have been dug up in a cave in what is now known as Gibraltar, shows that the Neanderthals were skilled engineers who had mastered the art of making glue.
“The structure revealed a hitherto unknown way in which Neanderthals prepared and used fire,” the researchers wrote in a new study, published Nov. 12 in the magazine. Quaternary Science Review.
Related: Did we kill the Neanderthals? New research may finally answer an old question.
The Neanderthal hearth looks deceptively simple at first: It’s a circular pit, about nine inches across and 3.5 inches deep (22 by 9 centimeters), with deeply cut walls. Two short channels about an inch long run to the north and south of the hole. But if the researchers are right, it is the work of real engineering.
A series of pictures retelling how a Neanderthal would have made glue on fire
Neanderthal technology in the Stone Age
Inside the furnace, the group found coal and a slightly burnt rockrose, a flowering shrub; small crystalline lumps of cool plant resin; and thin branches from local shrubs. They analyzed samples taken from the green walls and under the fire with gas chromatography-mass spectrometry, which identifies individual chemicals in a sample of materials. This produced residues of urea and zinc from guano (bird or bat), chemicals related to heat, and residues from protective wax on plant leaves.
The findings are the same one of the methods of testing another group of researchers produced Paleolithic tar in 2017. That original study showed a fire – actually a lot of buried oven – like this would have been enough to burn some plants to distill tar or resin for hafting tools.
To create these so-called glue factories, Neanderthals likely filled the hole with leaves from nearby rockrose trees, which release a sticky, dark resin when burned, the researchers of the new study wrote. Next, they covered the hole with wet sand and clay, probably mixed with guano to help seal the inside of the hole and keep oxygen out, which would prevent any flames from burning the contents to the core. Finally, they built a small fire on top using thin branches, which would burn the leaves of therockrose in the room below.
A photo of the coastal cave and a map of the interior
Every step of the process, and every fire itself, is carefully planned, the team said. It is easy to control the temperature of a fire made with thin twigs, and Neanderthals using a torch would have wanted to heat the leaves of the rockrose up to 300 degrees Fahrenheit (150 degrees Celsius), but not too hot. And they had to keep oxygen away from the leaves in the pit, because too much oxygen would let the resin burn instead of melt.
To test this method, Ochando and his colleagues built their own replica of the furnace, making enough resin to fire two spears. It took them about four hours from the time they started collecting the stone leaves to the time they finished cutting their spears – they even managed to pluck the spears from the village stone while the stone leaves were hot. Once the leaves burned, the archaeologists squeezed the melted resin from the leaves into shells from nearby beaches.
The image shows how Neanderthals used the area
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In doing this, Ochando and his colleagues realized that making resin may have been the work of two people.
“Our colleagues noticed during the archaeological excavations that they had to catch the fire that closed the plant and also open the shell. [the covering over the kiln],” study author Francisco Jiménez-Espejo, a scientist at the Andalusian Earth Sciences Institute, told Live Science in an email. He said the two vertical trenches on either side of the pit may have indicated where two Neanderthals dug into the pit, from opposite sides, to remove hot leaves before they cooled. That’s because it’s hard to “separate the tar” from the wet leaves, he said.
If Neanderthals really worked this way, they were not only good engineers, they were good at working together.