I don’t know about you, but I love a good Neanderthal story. At the beginning of the year, ASI ran a story about the discovery that Neanderthals had created stone tools held together by a multi-component adhesive, providing the earliest evidence of a complex adhesive in Europe and suggesting that these predecessors to modern humans had a higher level of cognition and cultural development than previously thought.  

Now, scientists have discovered a hearth in an excavation area of the Vanguard Cave, a natural sea cave in Gibraltar, that shows evidence of what one might be tempted to call the first adhesive and sealant "factory." The cave is part of the Gorham’s Cave complex, a UNESCO World Heritage Site that has provided archeologists with a lot of good evidence about how the Neanderthals lived. This latest piece of evidence gives us an idea of their understanding of using fire to create a new "technology."   

The researchers theorize that the hearth allowed Neanderthals to carefully and precisely control fire to create birch tar, which was then used to attach stone blades or other pointy structures to wooden handles by using the sticky substance and sinew or plant-fiber wrappings. Specifically, scientists explained that the hearth was "used for heating rockroses (Cistaceae) under anoxic conditions by burning herbs and shrubs, over a guano mixed with sand layer."

While archeologists have seen the use of fire as a source of heat, light, and possibly a tool to cook food, fire as a tool to develop new "technology" adds to our understanding of these early humans' capacity to manipulate their world with chemistry. In the published research paper on the subject, authors stated that the hearth "has revealed a hitherto unknown way by which Neanderthals managed and used fire."

The hearth is described as a round pit, approximately 9” wide by 3.5” deep with deeply cut vertical walls and two, inch-long trenches going north and south from the pit. It is theorized that Neanderthals filled the pit with leaves from the rockrose plant, covered the pit with a layer of wet sand and soil, which was likely mixed with guano to seal the inside of the pit and prevent oxidation. A small fire was built on the top, thought to be with grass and shrub, heating the rockrose leaves until they produced the sticky, brown resin. The hearth would have had to heat the rockrose leaves to around 300 °F, but much hotter.

The scientists working on the project conducted chemical analyses of the walls and floor of the hearth using many techniques, including gas chromatography-mass spectrometry. With this analysis, they came up with a theory about the process and materials used in the hearth to create the resin. They also replicated the process, conducting four experiments reproducing the size, morphology, materials, and dimensions of the hearth, confirming that the process did indeed work as they theorized. The research provides the "oldest evidence of Levoglucosan and retene in an archaeological context." The paper, titled "A Neanderthal's specialised burning structure compatible with tar obtention," was published in the November issue of Quaternary Science Reviews.

I share this story not to remind you that as much as you wish for a better measurement instrument or updated technology to make your job easier, at least you aren’t in a cave mixing guano with sand to seal your resin-producing hearth! I share it to remind us all that innovation and using the natural world to make our lives better has been going on for a very long time. And that readers of this publication, sitting in their labs developing new technologies, are a part of that very long history. I hope this issue of ASI gives you a bit more information as you work to on your new discoveries.

In December, we have included an article outlining the use of styrene-ethylene/butylene-styrene to help maintain the appearance and performance of adhesives and sealants over an extended period of time, an article about using viscosity-optimized aluminum hydroxide as a thermal conductive filler and flame retardant, and an article that discusses the use of adhesives when bonding dissimilar materials. Happy reading and enjoy the final days of 2024.