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Painting by Neanderthals? Study Makes a Design Inference

Photo: Cueva de Ardales, © João Zilhão, ICREA, via EurekAlert!

A longstanding question among both evolutionists and Darwin-skeptics is whether Neanderthals were capable of symbolic artistic expression. This debate has gone back and forth for years and a new study in Proceedings of the National Academy of Sciences adds to the conversation by making a detailed analysis leading to a design inference that supports painting by Neanderthals. The study looked at the Cueva (Cave) de Ardales in Málaga, Spain which contains flowstones that have been stained by iron. A nice example of what these iron-stained flowstones look like can be seen here. The question is whether the iron-staining is the result of natural processes (e.g., flowing water depositing iron oxide) or deliberate painting using some kind of an ochre-based pigment. The study ultimately makes a design inference — the iron-staining is the result of real Neanderthal painting — as Science Daily reports:

The origin and date of appearance of prehistoric cave art are the subjects of ongoing debate. Spain’s Cueva de Ardales is one point of discussion. There a flowstone formation is stained red in places. This colouring is apparently almost 65,000 years old but until now, a part of the scientific community attributed it to a natural coating of iron oxide deposited by flowing water.

However, that hypothesis has just been rejected by the findings of an international team of scientists including a CNRS researcher. The team members analysed samples of red residues collected from the flowstone surface and compared them with iron oxide-rich deposits in the cave. They concluded that the ochre-based pigment was intentionally applied, i.e. painted — by Neanderthals, as modern humans had yet to make their appearance on the European continent — and that, importantly, it had probably been brought to the cave from an external source.

Furthermore, variations in pigment composition between samples were detected, corresponding to different dates of application, sometimes many thousands of years apart. Thus, it seems that many generations of Neanderthals visited this cave and coloured the draperies of the great flowstone formation with red ochre. This behaviour indicates a motivation to return to the cave and symbolically mark the site, and it bears witness to the transmission of a tradition down through the generations.

Beautiful and Intricate Patterns 

Iron-staining is very common in porous sedimentary rocks as iron readily precipitates out of flowing water and iron oxide (rust) forms on the surface of the rock. This iron-staining often yields beautiful and intricate patterns, which can make it difficult to distinguish between naturally caused iron-staining and intelligently caused painting using iron-based pigments such as ochre. To address these kinds of questions scientists must use intelligent design reasoning, carefully analyzing to distinguish between naturally caused and intelligently caused features. That’s exactly what the authors of the study did here. 

In the technical paper they explain that the pattern of staining they observed is inconsistent with “natural geological processes”:

The staining cannot be interpreted as the result of natural geological processes typically occurring in caves such as fluvial flows, infiltration from soils, percolating waters, or weathering of the walls, either. Although flooding may coat the walls and even the roof of a cave, most accumulation occurs on the floors and is, in general, widespread. In Cueva de Ardales, traces of a deposit formed by flooding are visible neither on the floor nor on the walls of the chamber in which panel II.A.3 is located.

In other words, if the culprit was iron precipitating from water, then you’d expect to find stains not just on the flowstones and walls but also on the floor of the cave. But there is no staining on the floor or on other walls. 

Clay Particles and Flooding

They also used scanning electron microscope analysis to look at the shape of clay particles in the iron-staining, and found that their shapes were inconsistent with flooding:

In addition, clay platelets transported by flooding generally show under SEM broken or rounded edges, which is not the case with our samples.

Moreover, if water had deposited the iron oxide then it would have seeped into the flowstone, depositing the rust in three dimensions. Instead they found the ochre only appears on the separate layer over the surface of the flowstone:

Deposition of iron oxides by dripping water would produce a diffuse red staining of the calcite, while the deposit interpreted as paint occurs in the form of a distinct layer on top of and/or covered by calcite.

And quite oddly, when there is naturally occurring calcite covering the iron-staining, it contains no iron — an observation inconsistent with precipitation of the iron from water:

Ruling out the hypothesis that the presence of iron- and clay-rich minerals could be related to speleothem formation, the analyzed calcite sample includes neither…

This suggests that when water did flow down the flowstone it did not deposit iron. The authors also point out that “any iron-rich particles present in drip water would in any case not lead to the formation of the loose hematite and clay platelets seen in the pigments of panel II.A.3.”

A Conspicuous Location

Another observation that supports a non-natural origin is that the pigment appears only in a small, conspicuous location — an easily accessible and obviously visible section of stalagmites where one might expect painting to occur — with such features observed nowhere else in that part of the cave:

Weathering of the bedrock is the only process that could produce thin layers of well-preserved iron oxides and clay platelets but is inconsistent with the exclusive affection of a small area in the middle of a stalagmite located in a large room, on the walls of which no similar deposits are observed.

So far the authors have done a good job of ruling out natural causes. But what about making a positive case for intelligent causation? They do that too:

[I]n terms of morphology, the markings are characterized by a central area with high color density surrounded by an aureole that features a gradual reduction in the concentration of red matter. This pattern suggests an application of the paint by splattering as experimentally reproduced. 

In other words, they found a shading gradient pattern consistent with painting, not a natural process.

The authors go on to explore other possible explanations, but they think they’ve made a pretty strong case. The paper concludes: “Our results strengthen the hypothesis that Neanderthals symbolically used these paintings and the large stalagmitic dome harboring them over an extended time span.”

The Final Word? 

Will this study be the final word on Neanderthal art? Probably not. The authors make a good case, but as with so many aspects of prehistoric archeology, the evidence is indirect and not clear-cut. They even admit that what they found isn’t exactly what we typically think of as “art”:

[W]e hypothesize that panel II.A.3 is not “art” in the narrow sense of the word — “the making of objects, images, music, etc. that are beautiful or that express feelings” or “the activity of painting, drawing, and making sculpture” — but rather the result of graphic behaviors intent on perpetuating the symbolic significance of a space.

The authors made a design inference. Whether they’re right or wrong, the point is this: this study uses intelligent design reasoning, trying to discriminate between naturally caused iron-staining and intelligently caused painting. It provides yet another example showing that ID reasoning is a normal part of the scientific process.