Neanderthal adhesive manufacturing site found in Gibraltar cave

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Cut into a Gibraltar cliff face overlooking the Alboran Sea, a cave opening leads back in time to one of the earliest manufacturing sites on the planet—a Neanderthal-built tar distillation oven hidden for 65,000 years.

University of Murcia-led research has discovered a complex Neanderthal hearth structure in Vanguard Cave. Middle Paleolithic stone artifacts and residues suggest Neanderthals produced tar from rockrose plants (Cistaceae) here, showing off their advanced fire management and technological capabilities.

Neanderthals used fire for warmth, light, cooking, landscape clearing, and extracting adhesive tar from specific plants and trees. Evidence of their use of fire in tar extraction is based on the composition of the tar residues left on tools.

Tar was used as an adhesive for hafting stone tools to wooden handles, representing a significant advancement in tool-making, predating current modern human tar adhesive use by more than 100,000 years.

While the techniques Neanderthals used to extract tar have been previously back-engineered to suggest the use of underground fire pits, direct evidence of these pits has been missing from the record.

In the current study, "A Neanderthal's specialized burning structure compatible with tar obtention," published in Quaternary Science Reviews, researchers analyzed a hearth pit structure in Vanguard Cave, employing geochemical, mineralogical, palynological and micromorphological methods.

They identified a central fire pit with two opposite-sided trenches, revealing a crust of altered rocks and sediment due to prolonged fire use. This structure aligns with theoretical models requiring specialized heating installations for tar production under low-oxygen conditions.

Organic geochemical analysis revealed the presence of levoglucosan and significant amounts of retene in the structure's matrix, compounds associated with the combustion of resinous plant materials. Lipid analysis showed straight-chain n-alkanes of odd carbon numbers and n-alkanols of even carbon numbers, biomarkers indicative of fresh leaf wax from plants like rockrose.

Charcoal analysis uncovered partially vitrified remains of Cistaceae, or rockrose family plants, suggesting incomplete combustion under controlled conditions. Less than 10% of the charcoal was from conifer wood.

Palynological examination indicated the presence of abundant pollen grains within the structure, whereas surrounding sediments were free of pollen. This suggests the deliberate introduction of plant materials into the hearth by Neanderthals.

Micromorphological analysis showed no evidence of clay heating above 500°C, indicating that the structure was used for controlled low-temperature processes compatible with tar production.

Carbonate rocks within the structure appear placed intentionally, likely employed to maintain a seal composed of guano and sand. This seal would create a low-oxygen environment essential for effective tar distillation.

To test their hypothesis, the team conducted experimental archaeology by building a similar structure and using it to heat rockrose leaves under low-oxygen conditions. The experiment successfully produced tar sufficient to haft stone spearheads, using only tools and materials available to Neanderthals in the area.

Findings show Neanderthals organized complex fire-related activities by constructing specialized hearths for tar extraction. This confirms a level of cognitive complexity and cultural development previously expected based on their use of manufactured materials.

More information: Juan Ochando et al, A Neanderthal's specialised burning structure compatible with tar obtention, Quaternary Science Reviews (2024). DOI: 10.1016/j.quascirev.2024.109025

Journal information: Quaternary Science Reviews

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