The project has aimed to identify the organic binding agents and the bacterial communities of the sites through omics technologies, that is, those that study the totality of genes, organisms or proteins. It has done so through metagenomics techniques (a science that studies the DNA of microorganisms, extracted directly from environmental samples) and proteomics (the massive biochemical study of proteins).

Thus, the proteomic analysis of the pigment samples from three figures has allowed “the detection of casein peptides of bovine origin in the samples analyzed”, according to Clodoaldo Roldán, professor of Applied Physics and Electromagnetism at the University of Valencia and researcher at the ICMUV. “This finding allows us to hypothesize the use of animal milk as a binding agent, thus opening the hypothesis that the societies that made these paintings would practice livestock, placing themselves, therefore, in a chrono-cultural framework typical of the peninsular Neolithic (VI-III millennia BC)”, state the authors.

The research – in which the TRACES UMR 5608 laboratory of the Center National de la Recherche Scientifique of France has also participated. (CNRS) and the company Darwin Bioprospecting Excellence, S.L.–, has been developed with pigments from the Coves de la Saltadora shelter (Coves de Vinromà, Castellón), one of the most important decorated complexes in the Valltorta-Gassulla cultural park, a UNESCO World Heritage Site.

“We have carried out the first metagenomic analysis, that is, of microbial DNA, obtained directly from micro samples from three painted motifs (a archer, a caprid and a cervid) and a set of “control” samples corresponding to the wall in areas without pictorial motifs. "Metagenomics has provided us with the first description of the bacterial communities that colonize the patina of rock art and the parietal support, and that could have a protective effect on the paintings," according to the authors.

The composition of the pigments, that is, the raw materials used during the production of these paintings, is mainly composed of minerals based on iron oxides mixed with organic substances, which acted as binders, favoring their adhesion and resistance. Know these binders would allow us to understand the manufacturing processes, and favor obtaining radiocarbon dating, although identifying and characterizing these substances is complex due, among others, to the strong erosive process to which the Levantine shelters are subjected.

“Taking into account the open debate around the chronology and authorship of Levantine Art, our study provides objective arguments, compatible with a recent chronology for this graphic tradition, which could be linked to the first agricultural societies and livestock of the Iberian Mediterranean arc", according to the researchers.

Levantine rock art

The Iberian Mediterranean arc houses a unique graphic manifestation in European prehistory: Levantine rock art, declared a World Heritage Site by UNESCO in 1998. Currently the number of rock shelters decorated with these spellings exceeds a thousand, being the nucleus of Valltorta-Gassulla (l’Alt Maestrat, Castelló), one of the most notable territories due to the number of documented sites and the richness and interest of its panels.

Levantine art is a pictorial tradition that is located in shallow shelters of the inland mountains. Its uniqueness, in clear break with any previous graphic manifestation, is given by its strong naturalistic and narrative component. These paintings represent economic and social activities – hunting, honey collection or social conflicts – in which the male figure is exalted in his role as hunter and warrior. The information potential of these paintings is enormous, and their study and documentation has the objective of knowing and characterizing the author societies.

This research has been developed as part of the NEOSOCWESTMED project, a Marie Curie action developed within the framework of the seventh program of the European Commission, and within the "Projet Émergent 2016" program financed by the TRACES laboratory of the Center National de la Recherche Scientifique (CNRS) of France, in which ICMUV participates, I2SysBio and Darwin Bioprospecting Excellence, S.L.

Article:

Clodoaldo Roldán, Sonia Murcia-Mascarós, Esther López-Montalvo, Cristina Vilanova and Manuel Porcar: «Proteomic and metagenomic insights into prehistoric Spanish Levantine Rock Art». Scientific Reports volume 8, Article number: 10011 (2018) https://doi.org/10.1038/s41598-018-28121-6  

Link: https://www.nature.com/articles/s41598-018-28121-6.pdf  

Caption:

Floor plan of the Jumper's shelters showing the distribution of the analyzed rock figures and the control points.

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