Neanderthals’ 65,000-Year-Old "Glue Factory" in Gibraltar

Precision and Collaboration in Neanderthal Technology

Neanderthals, often regarded as robust and resourceful survivors of the Ice Age, have left yet another clue to their remarkable ingenuity. Archaeologists have uncovered evidence¹ of a 65,000-year-old hearth in Gibraltar that may have served as a "glue factory," used to produce tar for hafting weapons and tools. This discovery not only predates the arrival of modern humans (Homo sapiens) in the region by 20,000 years but also highlights the Neanderthals' sophisticated engineering and teamwork.

A Closer Look at the Neanderthal Hearth

The so-called glue factory, unearthed in a cave, appears at first glance to be a simple round pit, approximately 9 inches wide and 3.5 inches deep. The structure, however, reveals ingenious design. The hearth features sharply cut vertical walls and two small trenches extending north and south. Analysis of its remnants provides compelling evidence of a controlled, multi-step process designed to distill sticky tar from plants.

Vanguard Cave is one of several caves that Neanderthals once called home on the north coast of the Strait of Gibraltar. (Image credit: Juan Ochando et al. Quaternary Science Reviews; CC-by-4.0)

Inside the Hearth

Within the hearth, researchers identified several key components:

• Charcoal and partially burned plant material: Including rockrose, a shrub that produces resin when heated.

• Chemical traces: Urea and zinc from guano, indicating heat-treated organic materials.

• Plant wax remnants: From the protective layers of leaves used in the process.

Engineering Precision

The researchers hypothesize that the Neanderthals used this hearth to heat rockrose leaves in a low-oxygen environment, a critical step to extract resin without burning it. The process likely involved:

1. Lining the pit: Leaves were placed inside, covered with wet sand and guano to seal the chamber.

2. Controlled heating: A small fire of thin twigs was lit atop the sealed pit, providing the precise heat needed to distill resin at around 300°F (150°C).

3. Efficient extraction: Heated leaves were removed through the trenches, and resin was squeezed into shells for use.

“The structure has revealed a hitherto unknown way by which Neanderthals managed and used fire,” the researchers wrote in their findings, published in Quaternary Science Reviews.

Evidence of Experimental Archaeology

To confirm their hypotheses, the researchers recreated the Neanderthal hearth. Their experiment produced enough resin to haft two spear points in just four hours, including time spent collecting materials and knapping flint for spearheads.

The researchers built and tested a replica of the hearth, and after about four hours of work, they had enough resin to attach two stone points to spears. (Image credit: Juan Ochando et al. Quaternary Science Reviews; CC-by-4.0)

The experiment illuminated the likely collaborative nature of the process.

“Our colleagues noticed during the experimental archaeology experience that they needed to manage the fire covering the plant and also open the crust,” explained Francisco Jiménez-Espejo, a study co-author.

This division of labor suggests Neanderthals not only possessed technical skill but also practiced teamwork to achieve their goals.

Implications for Neanderthal Innovation

A Legacy of Glue-Making

Neanderthals are already known to have used adhesives like tar, resin, and ochre for hafting tools. This new evidence indicates they refined these techniques to an impressive degree, likely through trial, error, and innovation.

Advanced Problem-Solving

Producing tar in a controlled environment requires precise temperature regulation and an understanding of chemical processes. This discovery underscores the Neanderthals’ ability to manage complex tasks—an attribute once believed to be unique to modern humans.

Collaboration and Communication

The evidence of teamwork in this process adds another layer to the understanding of Neanderthal society. Effective communication and cooperation would have been essential, further challenging outdated perceptions of Neanderthals as unsophisticated.

Broader Context in Human Evolution

This hearth represents another chapter in the evolving narrative of Neanderthal ingenuity. It highlights how resourceful they were, thriving in diverse environments and developing technologies to meet their needs.

It would have taken several steps to put together a glue-making station, the researchers found. (Image credit: Juan Ochando et al. Quaternary Science Reviews; CC-by-4.0)

Moreover, the discovery adds to the growing body of evidence that Neanderthals were not merely surviving but innovating—adapting their tools and techniques to a variety of challenges well before Homo sapiens arrived in Europe.

“Every step of the process, and every feature of the hearth itself, was carefully planned,” the researchers concluded.

Conclusion

The discovery of this 65,000-year-old "glue factory" redefines the way Neanderthals are perceived, presenting them as skilled engineers, thoughtful planners, and cooperative collaborators. Their ability to manage fire, manipulate natural resources, and work together is a testament to the sophistication of their society. Far from being brutish relics of prehistory, Neanderthals continue to emerge as innovative, intelligent, and adaptive members of the human lineage.

1. Ochando, J., Jiménez-Espejo, F. J., Giles-Guzmán, F., Neto de Carvalho, C., Carrión, J. S., Muñiz, F., Rubiales, J. M., Cura, P., Belo, J., Finlayson, S., Martrat, B., van Drooge, B. L., Jiménez-Moreno, G., García-Alix, A., Lozano Rodríguez, J. A., Albert, R. M., Ohkouchi, N., Ogawa, N., Suga, H., … Finlayson, C. (2024). A Neanderthal’s specialised burning structure compatible with tar obtention. Quaternary Science Reviews, 109025, 109025. https://doi.org/10.1016/j.quascirev.2024.109025