Cut into the face of a cliff in Gibraltar, overlooking the Alboran Sea, Vanguard Cave has yielded a remarkable discovery that pushes back the timeline of human technological innovation. Here, researchers led by the University of Murcia have uncovered one of the earliest known manufacturing sites for tar production, created by Neanderthals roughly 65,000 years ago. The discovery reveals a complex hearth structure used by Neanderthals to distill tar from rockrose plants (Cistaceae), providing new evidence of their advanced fire management skills and technological capabilities.
Neanderthals are well known for their use of fire, which served multiple purposes including warmth, light, cooking, and landscape clearing. However, one of the most significant uses of fire involved the extraction of tar, a substance used as an adhesive for hafting stone tools to wooden handles. This practice represents a significant advancement in tool-making, as the use of tar for hafting predates its use by modern humans by more than 100,000 years. While the techniques Neanderthals employed for tar production have been inferred from indirect evidence, this new discovery offers direct evidence of the structures they used.
In their study, “A Neanderthal’s specialized burning structure compatible with tar obtention,” published in Quaternary Science Reviews, the researchers describe the hearth structure found at Vanguard Cave. This discovery is significant because, although archaeologists have long suspected that Neanderthals used underground fire pits to extract tar, no such direct evidence had been found until now.
The researchers used a range of advanced analytical techniques, including geochemical, mineralogical, palynological, and micromorphological methods, to examine the structure of the hearth. What they found was a central fire pit surrounded by two trenches on opposite sides. These trenches contained a crust of altered rocks and sediment, which indicated prolonged exposure to high heat. This configuration fits with models suggesting that specialized heating systems were needed for tar production under low-oxygen conditions.
Organic geochemical analysis of the hearth revealed the presence of levoglucosan and large amounts of retene—compounds typically associated with the combustion of resinous plant materials. This finding supports the hypothesis that Neanderthals used fire to extract tar from rockrose plants, a process that involves heating plant materials under low-oxygen conditions to distill the tar. Lipid analysis of the hearth’s residues showed straight-chain n-alkanes of odd carbon numbers and n-alkanols of even carbon numbers, both of which are biomarkers of fresh leaf wax from plants like rockrose.
Charcoal analysis provided additional insights, showing that the hearth contained remains of Cistaceae (rockrose) plants, which had been partially vitrified due to incomplete combustion under controlled conditions. In contrast, less than 10% of the charcoal was from conifer wood, indicating a deliberate selection of plant materials for the tar extraction process. Palynological analysis revealed abundant pollen grains within the hearth structure, which suggests that Neanderthals intentionally introduced plant materials into the fire, further supporting the idea that they were actively managing the environment for tar production.
Micromorphological analysis provided further confirmation of the controlled conditions of the hearth, showing no evidence of clay heating above 500°C. This suggests that the hearth was used for low-temperature processes that are compatible with tar production, where high heat is avoided to preserve the integrity of the tar.
Interestingly, researchers also identified the intentional placement of carbonate rocks within the structure, likely used to create a seal made of guano and sand. This seal would have reduced the oxygen levels inside the hearth, creating an ideal low-oxygen environment necessary for effective tar distillation.
To test their hypothesis, the researchers conducted experimental archaeology by constructing a similar structure and heating rockrose leaves under low-oxygen conditions. The experiment successfully produced tar that could be used to haft stone spearheads, replicating the process that Neanderthals would have used. This hands-on experiment confirmed the practicality of the hearth design and provided further evidence of Neanderthal ingenuity.
The discovery of this complex hearth structure at Vanguard Cave demonstrates that Neanderthals had a high level of cognitive and cultural development. Their ability to organize and manage fire-related activities for specialized purposes, such as tar production, shows that they were capable of complex technological innovations. This finding adds to the growing body of evidence that Neanderthals were not only adept at using tools but were also skilled in creating and manipulating materials in ways that were once thought to be unique to modern humans.
This research offers a new perspective on Neanderthal life, suggesting that they had a more sophisticated relationship with their environment and resources than previously thought. It challenges traditional views of Neanderthals as primitive and underscores their capability for innovation, planning, and cultural complexity. The ability to manufacture tar from plant materials not only highlights their technical skills but also sheds light on the advanced ways in which Neanderthals engaged with the natural world, opening up new avenues for understanding their technological and cognitive achievements.