Archaeologists recreated three common kinds of Paleolithic cave lighting

In 1993, a media studies professor at Fordham University named Edward Wachtel visited several famous caves in southern France, including Lascaux, Font-de-Gaume, Les Combarelles, and La Mouthe. His purpose: to study the cave art that has justly made these caves famous.  Wachtel was puzzled by what he called “spaghetti lines” on the drawings, partially obscuring them. There were also images of, say, an ibex with two heads, a mammal with three trunks, or a bull drawing superimposed over the drawing of a deer.

His guide for the La Mouthe tour was a local farmer, and since there were no electric lights in this cave, the farmer brought along a gas lantern. When the farmer swung the lantern inside the cave, the color schemes shifted, and the engraved lines seemed to animate. “Suddenly, the head of one creature stood out clearly,” Wachtel recalled. “It lived for a second, then faded as another appeared.” As for those mysterious spaghetti lines, “they became a forest or a bramble patch that concealed and then reveled the animals within.”

Wachtel subsequently published a paper entitled, “The First Picture Show: Cinematic Aspects of Cave Art,” in which he concluded that the cave drawings were meant to be perceived in three dimensions—one of them being time. These could have been the first “protomovies,” he thought.

It’s an intriguing take, although it must be said that Wachtel’s ideas are speculative. There is no way to definitively prove what those prehistoric cave artists intended, and therefore it’s unwise to draw strong inferences about these being cinematic in nature, or to assume that this tells us anything about prehistoric artists’ conception of time. But his point about the importance of viewing cave paintings under the lighting conditions in which they were created and viewed in prehistoric times is sound.

Wachtel’s story recently resurfaced in a Twitter thread, and it couldn’t be more timely. Lighting sources could indeed hold vital clues to the different ways prehistoric peoples used caves, according to a new paper by a team of Spanish scientists, published in the journal PLOS ONE. They conducted in situ experiments with three different kinds of Paleolithic lighting sources, in the hopes of shedding some light (pun intended) on what those various illumination methods might tell us about the emergence of “human symbolic and artistic behavior” in the form of cave art.

There are nearly 350 such prehistoric caves in France and Spain alone, including the oldest cave painting yet known: a red hand stencil in Maltravieso cave in Caceres, Spain, likely drawn by a Neanderthal some 64,000 years ago. (The oldest known depiction of an animal was discovered in 2018 on the island of Borneo in Indonesia, dating back 40,000 years.) The Spanish team chose to conduct their experiments at the Isuntza 1 Cave in Spain’s Basque country, and selected two distinct spaces in particular.

The first was a large, wide chamber with walls of bedrock, with 99.7 percent relative humidity and an average temperature of 17.6 degrees C (63.6 degrees F).  They thought it would be ideal as a “staying chamber” for the experiments The second space was a second, slightly smaller chamber with similar relative humidity (99.9 percent) and average temperatures (14.2 degrees C, or 57.5 degrees F) similar to the first space. The two spaces are connected by a rough passage 40 meters long (about 131 feet).

The Spanish researchers chose lighting types for their eight experiments based on known archaeological data: five torches tested in both spaces and the passage, as well as two stone lamps with animal fat, and a small fireplace, both tested just in the first space. All the torches were made from dry juniper branches joined together, like the remains of ancient torches found in the Aldene and Reseau Clastres caves. The researchers included a bit of birch to act as tinder, and added pine resin, animal fat, or a combination thereof to assess how well different fuel types worked.

The lamps were replicas of a sandstone lamp found in La Mouthe Cave in Dordogne, France. They used bovine animal fat as fuel, with three juniper wicks, arranged in a teepee shape inside the lamp. They also built a small fireplace on a clay substrate in the first chamber with juniper and oak as wood fuel.

For all the lighting experiments, the team measured how long the lighting source lasted (duration); the total amount of light reaching a specific surface or point relative to the human eye (illuminance, or lux); how much illumination was emitted in certain directions (luminous intensity); the minimum distance between the light source and total darkness (action radius); and luminance, which connects light intensity with the surface of the source. They also kept track of the highest temperature reached by each type of lighting source.

Those measurements showed that the various lighting sources had very different characteristics, and thus were probably used in different contexts. The wooden torches, for instance, emitted light in all directions, up to nearly six meters (19.6 feet), and lasted an average of 41 minutes. The torches exhibited uneven light intensity, and often needed to be relit by waving them from side to side, and they produced a lot smoke. So they worked best for exploring caves or crossing wide spaces. The team also found that adding resin intensified the flame, while adding animal fat extended its duration.

In contrast, the grease lamps emitted weaker light akin to the intensity of a candle, over a span of three meters (9.8 feet) or so. They burned consistently, and didn’t smoke, for over an hour, but they had a dazzling effect if the person was moving and didn’t illuminate the floor very well. Also, “It was necessary to maintain constant control over the wick to prevent it from sinking into the fatty fuel, causing the flame to be extinguished,” the authors wrote. This makes the lamps better suited for lighting small cave spaces over a longer period, complementing the advantages of the torches.

As for the fireplace—the only truly static system—its illumination covered a range of 6.6 meters (21.6 feet). However, it burned for just 30 minutes and gave off a lot of white smoke, making it unsuitable for use unless there were strong enough air currents to disperse that smoke. “The fireplace location was not appropriately placed regarding air currents,” the authors noted, which are “essential to achieving a prolonged stay underground. However, in the case of large fires, convection currents are produced, and they would be efficient enough to evacuate gases outside of the cave.”

The Spanish team also built a virtual 3D model of a section of the Atxurra cave known as the Ledge of the Horses. It’s a naturally formed platform just above a passage floor, with two panels of about 50 animal engravings: bison, goats, horses, and hinds, many of them overlapping. The ledge was also littered with scattered charcoal, lithic tools, and ashes from three probable fireplaces. In the virtual model, they conducted a spatial analysis of all three tested lighting sources.

The modeling showed that the decorated panels would be “barely perceptible” to someone standing in the lower parts of the gallery, even if that person were carrying a lamp or a torch. It would need to be illuminated from the top of the ledge to be seen. In contrast, the fireplaces appeared to be strategically located to illuminate the entire decorated space. Torches did prove to be a good lighting source for accessing that space, however, with an estimated travel time of 38.39 minutes—in line with the measured duration of the torches. “It does not seem by chance that the optimal routes estimated to access this space are covered with scattered charcoals, surely fallen from the torches used in the Magdalenian period,” the authors wrote.

The findings have no direct bearing on Wachtel’s speculation about prehistoric cinematic art. But the more archaeologists learn about Paleolithic lighting sources, the more we will understand about how those lighting sources affect human perception in a cave environment, with implications for the emergence of cave art. That’s why the Spanish team thinks it is essential to continue conducting these kinds of experiments.

“Only with a large corpus of archaeological remains, including different types of lighting systems (and fuels), studied through an interdisciplinary approach, will it be possible to adequately reproduce Paleolithic light resources,” they concluded in their paper, “Our experiments in Paleolithic lighting point to planning in the human use of caves in this period, and the importance of lighting studies to travel the activities carried out by our ancestors in the deep areas of caves. “

DOI: PLOS ONE, 2021. 10.1371/journal.pone.0250497  (About DOIs).

https://arstechnica.com/?p=1773827