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Neuroscience sheds more light on ancient abstract engravings

By 4th July 2019 July 8th, 2019 No Comments

A study by researchers in Bordeaux has reinforced the hypothesis that our ancestors attributed perhaps symbolic meaning to abstract motifs inscribed in stones, eggshells or shells relatively early on in prehistory. The result, obtained by mapping the regions of the brain of volunteers using functional magnetic resonance imaging (fMRI) while they were presented with tracings of engravings dating from between 540 000 and 30 000 years ago, shows that the abstract patterns are analysed by the same area of the brain that recognizes objects. They also activate a region of the left hemisphere that is known to process written language. The research is reported in Royal Society Open Science.

Fig_Mellet_eng

Engraving discovered at the Blombos site (South Africa) dating back 75 000 years. Centre: Example of visual categories used in the experiment. Bottom: Lateral and inferior views of brain activations caused by the perception of engravings located in the occipital lobe and the ventral part of the temporal lobe (LH: left hemisphere, RH: right hemisphere, Inf: inferior view). These activations are comparable to those caused by the perception of everyday objects. Courtesy: Francesco d’Errico and Emmanuel Mellet

Many researchers believe that humans underwent a cognitive revolution with the arrival of the first modern populations in Europe 42 000 years ago. Others say that ornamental objects, pigments and abstract engraving on African sites dating back more than 100 000 years are proof that symbolic practices were already around this long ago. Other studies still show that Neanderthals and other “archaic” populations also showed symbolic behaviours.

The Bordeaux researchers, who are from the Pacea laboratory and the Groupe d’imagerie neurofonctionnelle (GIN-IMN) led by Francesco d’Errico and Emmanuel Mellet, studied a small batch of abstract engravings discovered on African and Eurasian sites that are over 40 000 years old. To understand the nature of these artefacts, they mapped the blood oxygen level-dependent (BOLD) signal in 27 healthy volunteers while they looked at the engravings. They then compared these signals with those obtained when the volunteers were presented with other types of representations, including objects, words, landscapes and an ancient alphabet (the linear-B syllabic script) that the participants were unfamiliar with.

We now know that the human visual system is organized hierarchically, with primary areas analysing the elements that constitute an image (its contrast, colour and orientation) and secondary areas distinguishing the different visual categories. Some brain areas are thus more specialized in analysing landscapes while others in analysing objects or writings.

The team found that the brain zones activated by the prehistoric engravings activate the same brain zones as objects and and only marginally modified the activity of areas related to looking at landscapes or the ancient alphabet. This result confirms that the oldest abstract engravings have visual properties that are similar to those of objects to which meaning can be attributed, say the researchers. What is more, the engravings activated a lateralised area of the brain in the left hemisphere that is known to be involved in processing written language. Again, this strengthens the idea that these engravings might have served as a means of communication for the first humans – as suggested in previous non-experimental studies.

Read the research paper: Mellet E, Salagnon M, Majkić A, Cremona S, Joliot M, Jobard G, Mazoyer B, Tzourio-Mazoyer N, d’Errico F. 2019 Neuroimaging supports the representational nature of the earliest human engravings. R. Soc.open sci.6: 90086.