I would like to include a quick note on the definition of entoptic imagery : In their discussion of paleolithic cave imagery, Lewis-Williams and Dowson define entoptic imagery as visual experiences arising from anywhere within the optic system, which includes the eyes, the occipital lobe of the brain, and the many other portions of the neural cortex that process visual stimuli. This definition comes from the Greek translation of entoptic meaning “things perceived within vision”, and is commonly used by anthropologists and archaeologists (Williams & Dowson 1988). On the other hand, in most medical literature, entoptic imagery is defined as imagery which only originates from within the eye itself. Given the Greek meaning of the word entoptic, I prefer the anthropological definition of the term. Therefore, for the purposes of this article, ‘entoptic’ indicates imagery that arises from anywhere within the visual system, from the eyes to the neural cortex.
In 2011, Genevieve Von Petzinger mapped out the Geometric Patterns of the Paleolithic world, identifying 26 distinct shapes. She then looked for patterns of continuity and change over time and space. She found that at an early age we already see 70% of the patterns being used, and that there is a high degree of repetition of a limited number of shapes, with some being replicated throughout the 20,000 year time span of the study. This suggests that these symbols were not created at random, but that they were intentional and symbolic. Von Petzinger believes that the abstract nature of these signs is some of the best proof we currently have that these images were not being made purely for their aesthetic qualities, and she suggests that these markings were symbolic attempts to communicate ideas that were not so easy to depict in a physical form.
This theory goes directly in line with the theory of Lewis-Williams and Dowson. If these images are, in fact, depictions of entoptic imagery seen during trance, and if these images are consistent across individuals and types of trance state, it would make a great deal of sense that we see these images in so many different parts of the world and that they are consistent throughout a very long period of time. If the trance state and the brain itself does not change significantly across individual and method of trance induction, there would be no reason for the images to do so, either!