Traces of an old "glue" on a stone tool of 50,000 years ago point to a complex thinking of the Neanderthals, experts say.
The glue was made from birch tar in a process that required advance planning and involved several different steps.
It is becoming increasingly clear that we have underestimated the capabilities of our evolutionary cousins.
Only a handful of Neanderthal tools show evidence of glue, but experts say the process may have been widespread.
The tool found in the Netherlands has spent the last 50,000 years under the North Sea. This could have contributed to the preservation of the tar glue.
Co-author Marcel Niekus of the Foundation for Stone Age Research in Groningen said that the simple stone flake was probably used either for cutting plant fibers or scraping animal skins.
While birch tar was sometimes used by Neanderthals to attach stone tools to wooden handles, this particular tool probably had only one handle of tar. Dr. Niekus said there was no imprint of a wood or bone stem in the tar.
It would have allowed the user to put more pressure on the stone flake without cutting their hands ̵
The tool was made by Neanderthal groups living on the icy borders of their range, say the authors of the study. At that time, this area was part of Doggerland, a landmass that today lies under the North Sea.
These small hunting groups inhabited the icy tundra with relatively few trees.
"You really had to plan ahead, as the process requires at least 40 kg of wood, which is not easy to collect in steppe tundra conditions because there are only dwarf birch trees," Dr. Niekus told BBC News.
They also had to invest time and energy in building the fire and extracting the tar. "
Researchers used to think Neanderthals would only have attached certain types of special tools, such as tips and scrapers (attaching a handle or strap to a cutting edge).
The Dutch discovery shows that "they also cling to very simple, ugly flakes," Dr. Niekus. "We did not expect that."
"With the time required, one would expect to do it only with special hunting weapons, but they also did it with special household tools. We believe that the use of birch tar was fairly common. "
There are hundreds of Neanderthals in the Netherlands, but birch tar is rarely found." Marcel Niekus believes that this is due to the fact that the tar is not preserved under normal conditions under the North Sea were perfect for the preservation of the tar and offered "a tiny window to Neanderthal normalcy."
"The important aspect of our finding is that we can demonstrate this from the various known methods for distilling birch bark pitch. Neanderthals used the more complex ones," said co-author Dr. Gerrit Dusseldorp of the University of Leiden.
"These are more efficient and the distribution of tar impurities that we can see on CT scans is similar to that in complex distillation processes. "Birch tar is also found in Neanderthal contexts in Campitello, Italy, 200,000 years ago and in Königsaue, Germany, where the evidence is 50,000 years old.
Neanderthals in Italy may also have had pine resin for gluing 50,000 years ago However, this natural substance is not as supple and lets the researchers suggest that birch tar was their first choice, and there are also traces of bitumen found in the Neanderthal context 42,000 to 70,000 years ago.
The stone tool was made on the beach of Zandmotor near The Hague found the same sandy strata that gave rise to a Neanderthal skull fragment Carbon dating of the tar showed an age of approximately 50,000 years.
"Modern people in South Africa have been known to use adhesives from a time ago 100,000 years ago, "Dr. Dusseldorp told BBC News earliest known N eandertalerfund. However, as such findings are rarely conserved, this does not definitively prove that there are no older modern human adhesives. We just have not found her yet.
The article that describes the find is published in Proceedings of the Journal of the National Academy of Sciences (PNAS).
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