At a well-known hangout of Neanderthals, archaeologists have uncovered a structure they believe was used to cook up a form of prehistoric glue.

The discovery was made in Vanguard Cave, part of Gorham's Cave complex, in the British overseas territory of Gibraltar. Located on the seafront overlooking the western Mediterranean, the caverns are thought to be one of the last known habitations of the Neanderthals in Europe before they drifted into extinction.

In a layer of sediment dated around 67,000 to 60,000 years old, the researchers uncovered a hearth structure that they say was “clearly” built by human hands.

With further work, they found evidence that the hearth was used to create birch tar, a gloopy substance that was used by prehistoric humans to attach a handle to a tool or weapon (known as hafting in the weaponsmith business).

Firstly, the structure was circular, featuring two channels and a thick wall lining, suggesting a more complex construction than a typical cooking fire pit. 

Secondly, the hearth was dotted with chemical traces that suggest the combustion of resinous plant material. This includes charred wood and microscopic ash fragments, as well as plant compounds that are often associated with the production of tar from birch bark and similar plants.

The strands of evidence led the team to propose that the structure was used for heating a flowering plant, rockroses (Cistaceae), under anoxic conditions by burning herbs and shrubs. 

They even backed up their theory by building a similar structure and carrying out an experiment to see if they could cook up some birch tar. 

“Distilling a small bunch of young leaves of rockrose for a reasonable period of time in a closed and almost anoxic environment enabled to produce tar that was more than enough to haft two spearheads, using only tools and materials available in the area for the period in reference,” the study authors write. 

The process of crafting a gooey glue-like substance from raw ingredients, and then using it to enhance complex tools, could be seen as evidence for Neanderthals possessing a high level of intelligence. Some anthropologists have claimed it shows our sister species must have had some grasp of combustion and basic chemistry, not to mention a strong degree of cooperation and communication.

Contrary to the outdated stereotype of hunched-over brutes, Neanderthals were anything but dunces. Cave-loads of evidence now show their sharp intelligence, intricate cultural practices, and profound emotional depth.

It’s just a shame their glue-making skills couldn’t save them from extinction. 

The study is published in the journal Quaternary Science Reviews.