Assessing the accessibility of Atxurra

Cave painting is one of the earliest forms of human culture, one of the first outlets of our creativity. But the meaning that these paintings had to the communities who created them remains a bit of a mystery. Who painted them and for what purpose? In this month’s ‘Science Notes’, we are highlighting a recent study that has attempted to provide some answers to these questions by examining and mapping the terrain of the caves where rock art frequently appears. By quantifying the accessibility of these areas, it is hoped that we will better appreciate how these painting feats were achieved.

Qualitative analysis of cave accessibility is not new, with various methodologies developed over the decades describing degrees of difficulty. Through such efforts we know that, even though the salle des peintures in the cave of Etxeberri in the Basque Country is only 150m from the entrance, it is much more difficult and dangerous to get to than the salon noir in Niaux cave in south-west France, which is more than 800m from the entrance. But, before now, the difference between these two spelunking efforts could not be quantified and comparisons between larger groups of cave systems were almost impossible to make.

ABOVE Using a combination of 3D modelling, experimental archaeology, and GIS,researchers have been able to create an accessibility model for cave art.
Using a combination of 3D modelling, experimental archaeology, and GIS,researchers have been able to create an accessibility model for cave art. IMAGE: Intxaurbe et al., Journal of Archaeological Science (2021).

Enter this recent effort to develop an accessibility model. The researchers on the project used a case study of one particular cave: Atxurra, also in the Basque Country. This cave was first discovered in 1929, but it was not until 2015 that a rock-art ensemble – comprising more than 113 engraved and painted animals in the Upper Magdalenian style – was discovered deep within the cave (between 186m and 366m from the prehistoric entrance).

To figure out the likely routes these Palaeolithic people would have used to access these areas of the cave, researchers first needed to recreate how the cave would have appeared when the art was created. Using knowledge of karst geomorphology and a 3D laser scan of the cave, they were able to determine the changes that had occurred to the cave in the intervening millennia. This is a technique that has been used successfully in several other caves with notable rock art, including at Lascaux in France.

The researchers then assessed the cost of movement using experimental archaeology techniques. With the help of more than 20 volunteers with spelunking experience, the researchers tracked how they navigated the 4.7km-long cave-system of Lamiñak, which is located only 300m from Atxurra, while also monitoring their vitals to assess how physically taxing certain aspects of the climb were. During their attempts, the volunteers were either barefoot or wore neoprene socks to mimic Palaeolithic soft footwear. They also carried a torch in one hand (as our prehistoric predecessors unfortunately did not have access to headlamps), meaning that they could only navigate the terrain using one hand. Through this experimentation, the researchers were able to gather data on how travel rates differed depending on the terrain of the cave (shafts, cornices, ramps, and so on) and the impact that this had on each individual’s heart rate.

By combining the prehistoric conditions of a cave with the modelled travel rates from the experimental phase of the project, the researchers were then able to develop a complete 3D accessibility model for caves using GIS (geographic information systems). When they applied their model to Atxurra, they found that, even though there are plenty of large, flat panels in the cave that would have been easy to reach in the Palaeolithic, the prehistoric artist (or artists) appears to have specifically chosen those which were the most difficult to access. To be able to reach these panels would have required great caving experience, as well as possibly a team of people working together. Even then, they probably would have had to have used certain types of climbing technology, such as ropes, to be able to haul painting materials into these hard-to-reach areas.

If this model can be successfully applied to other caves and cave systems, it will allow researchers to make broader comparisons between them and to determine whether the pattern seen at Atxurra was common across Europe or whether there may be more regional variations on panel choice and location.