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Engraved hexagons on an Ice Age ivory: a neurological perspective on an anthropological debate
  1. G D Schott
  1. Correspondence to Dr G D Schott, The National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK; g.schott{at}ucl.ac.uk

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Introduction

In the spring of 2013 an exhibition entitled ‘Ice Age art: the arrival of the modern mind’ was mounted at the British Museum in London.1 Numerous objects created from 40 000 years to 20 000 years ago towards the end of the last Ice Age were displayed, and many of them showed intricate carvings including figurative sculptures and engraved drawings, as well as artefacts and ornaments variously decorated with simple or complex patterns and designs. Among these exhibits was a decorated mammoth ivory plaque about 21 000 years old found at Eliseevitchi, midway between today's Moscow and Kiev. On this 19.1 cm long ivory is a remarkable design: a network of hexagons forming honeycomb lattices which are remarkably well preserved and clearly visible (figure 1). From left to right the lattice pattern is ‘formed by slightly elongated hexagons that become broader lozenges and then revert to hexagons’.1

Figure 1

Mammoth ivory, found at Eliseevitchi. Length 19.1 cm. Reproduced (in colour in the online version) with permission from the Collection of the Peter the Great Museum of Anthropology and Ethnography (Kunstkamera), Russian Academy of Sciences, MAE no. 5298-2850.

What inspired the carving of such a specific and complex pattern? Anthropologists have sought to explain how such engravings originated and what they represented, and, intriguingly, a number of authors have invoked neurological explanations. As discussed below, however, while some of their explanations are far from compelling, many are pertinent to speculations on the neurological processes subserving the engraving's realisation, and on whether the brains of Ice Age humans—anatomically the same as ours—powered artistic creativity similar to our own.

How did the engravings originate?

Three possibilities suggest themselves for what led the engraver to create the network of hexagons. First, he (or she) may have observed and ‘copied’ structures or patterns consisting of hexagonal objects he had seen. Second, he may have been inspired by patterns generated intrinsically by the visual system within the eye or, more relevant here, the brain. Third, the decoration may have been entirely original, and created without any obvious ‘template’. Each possibility leads to some conjectures concerning cerebral function in Ice Age people.

Did the engraver copy a hexagonal pattern?

First, if the engraver was inspired by observing hexagonal patterns in nature, what structures with this pattern were there to be seen and copied? One anthropological suggestion has been that the ivory's hexagons resemble the pattern of fish scales, or symbolise a fish.2 This explanation seems unlikely, however, since although fish remains were found in the Eliseevitchi region, as Murray commented: ‘I know of no species of fish with two different kinds of scales on its body’.3 Another suggestion is that the pattern of hexagons represents the bees’ honeycomb. Honeycombs in the wild tend to form nested catenary curves rather than the more rigid structure familiar to beekeepers today, and such wild honeycomb appearances are relevant to form constants discussed below. Turtles and tortoises have carapaces with hexagonal markings too, but, like bees, these creatures were not present in the harsh cold environment. It is also unlikely that Ice Age people ever saw hexagonal interlocking basalt columns, as occur in the Giant's Causeway, as this type of volcanic formation is unknown in this region.

If, however, the patterns had indeed been observed and copied from nature, it is reasonable to postulate that many thousands of years ago the same or similar regions of the brain known today to be associated with copying would have been enlisted. These regions include the primary motor cortex, prefrontal cortex and posterior parietal cortex,4 with the right parietal lobe being particularly implicated in the processing of spatial relationships, and the left parietal lobe with spatial organisation.5

Do entoptic phenomena account for the hexagons?

Second, the visual pattern might have been generated within the engraver's brain, and then remembered. Such visual, so-called entoptic phenomena include ‘form constants’ or ‘hallucinatory constants’6—the names given by Heinrich Klüver, who noted that hallucinations experienced during the early stages of mescaline intoxication were ‘remarkably uniform as to the appearance of [their] forms and configurations’.6 Among the diverse patterns of these form constants, the honeycomb pattern comprising multiple hexagons is a particularly well recognised example. Klüver also noted the variety of circumstances in which form constants appear, including falling asleep and waking from sleep; gazing at the ceiling; viewing flickering lights or rotating disks; hypoglycaemia; when febrile; in schizophrenia; and during migraine attacks.6 The latter circumstance, together with hallucinations associated with hallucinogenic drugs and trance states, may be particularly pertinent.

It is in the visual aura of migraine that the most precise hallucinatory patterns have been illustrated,7 notably those reported and illustrated by Richards detailing his wife's visual aura.8 However, chiming with Hubel and Wiesel's findings on the orientation specificity of responses of monkey striate cortical cells,9 while entoptic zigzag patterns are frequently experienced and sometimes depicted, hexagons are not. Thus Podoll and Robinson found very few reports of hexagons and honeycombs ‘seen’ during migraine attacks, although they encountered a number of ‘lattice’ hallucinations in their collection of migraine art.10 Furthermore, in his discussion of the cerebral processes subserving visual aura, Richards had to insert radial lines to join up the zigzags to form hexagons (figure 2).8 Thus, at best, the Eliseevitchi ivory engraving could have been inspired by migrainous visual aura but it is most unlikely to represent a copy.

Figure 2

A honeycomb of hexagons emerges when the thin radial lines are added to the zigzag patterns seen during the visual aura of migraine. Adapted, with permission from Scientific American, from Richards, 19718.

Although entoptic hallucinations including hexagons and honeycomb patterns are well known to occur under the influence of plant-derived hallucinogenic drugs such as mescaline,6 ,11 it is highly improbable that hallucinogenic plants were available to Europeans at the end of the last Ice Age.12 But entoptic hallucinations have also been associated with shamanism, an aspect which has attracted considerable attention from the anthropological perspective.12–15 The shaman—a ritual specialist who goes into a trance for spiritual, healing or other purposes—is said to progress through stages of the trance associated with increasing alteration of consciousness. Although the evidence has been vigorously challenged,12 Lewis-Williams and colleagues have argued both that shamanism existed in the Ice Age during the Upper Palaeolithic in Europe, and that during the early stages of the trance the shaman typically ‘sees’ those geometrical shapes which recall Klüver's form constants.14 ,15

However, even if experiencing visual hallucinations under the influence of drugs or during a trance, the Ice Age engraver would inevitably be incapable of precision carving, and would either have to rely on a memory of the honeycomb pattern, or relive the pattern, perhaps as a result of visual flashbacks.11 ,14 In the visual aura of migraine the hallucinations are mainly generated in the visual cortex, but it is less clear which parts of the visual system are responsible for other entoptic phenomena. Surprisingly, form constants such as hexagons are not typically generated by electrical stimulation of the occipital lobes,6 although geometrical and other complex entoptic patterns have been reported when subjects simultaneously received hallucinogenic drugs.16

Did the hexagon pattern emerge as a creative act de novo?

If, as implied by the foregoing comments, and in opposition to some anthropologists’ views, there is little compelling evidence that the hexagons on the ivory are attributable either to objects seen in nature or to entoptic phenomena, the third possibility becomes more attractive: the hexagonal pattern emerged de novo as an act of original creativity—‘the mental journey between ideas or concepts that involves either a novel route or novel destination’.17 This requires ‘the ability to hold an image ‘in the mind's eye’’, together with those ‘neural changes required for this fundamental shift in artistic potential’.18 Perhaps the engraver simply used hexagons, one of only three regular shapes which tessellate without gaps or overlaps, to decoratively ‘tile’ part of the tusk. Whatever the artist's motives, various theories for the neurobiological basis for all such creativity have been suggested;17 mechanisms subserving creativity and the parts of the brain concerned with imagery and modulating creativity however remain elusive,19 even more so in prehistoric man.

Abstract symbol or representational ‘art’?

Accepting the likeliest possibility that the honeycomb pattern on the ivory was an example of original creativity, is the pattern an abstract symbol or a figurative representation which might loosely be termed ‘art’, acknowledging that the distinction is arbitrary—witness Gombrich's expression ‘Ornament as Art’?20 And to add a further twist, regular patterns—perhaps such as those on the Eliseevitchi ivory—may even represent a system of notation, mnemonic aid or recording device, blurring the distinction between an artistic creation and a tool.21

If the hexagons comprise abstract patterns and derive from form constants—whether generated spontaneously, or from migraine, hallucinogenic drugs or mind-altering rituals—they are surely not representational or figurative ‘art’? If, however, the mammoth ivory has been embellished so as to depict a fish with its scales, surely that is such ‘art’? The evidence outlined above favours the conclusion that this network of hexagons was an abstract, symbolic creation, and decorative rather than utilitarian,22 a conclusion which leads to some further neurological observations.

What cerebral processes subserved the creation of the network of hexagons?

The two forms of artistic creativity—abstract and representational—would likely have been subserved by distinct neural processes: using functional MRI, studies of images in respect of their colour, movement and line led Zeki to the ‘general rule…that all abstract works activate more restricted parts of the visual brain than narrative and representational art’.23 The capacity of the brain more generally to power the artistic creativity which led to the emergence of art during the Ice Age is thought to be associated with an overall increase in brain size, and, more importantly, with the specific growth of the frontal lobes and the increased computational capacity of cortical neurons, perhaps including the potential for massive parallel processing.24 In passing, the perception of beauty, an invaluable facility for the artist and the appreciative viewer, is an attribute of the prefrontal cortex25 which would have participated in the enlargement of the frontal lobes. During primate evolution there was great enlargement too of the temporal-parietal-occipital junction and angular gyrus;22 these structures have been implicated in the convergence of processes subserving proprioception and vision,26 which would have enabled the eye-hand coordination necessary for the intricate carving of complex design.

The motor skills necessary for precision engraving

However the hexagonal pattern was conceived, the pattern was realised by an extraordinarily skilled feat of intricate craftsmanship: each side of the numerous hexagons is 2–3 mm long, and was carved using a burin on hard ivory. Such precision demands exquisite motor control, a function that likely implicates the corticospinal tract but more particularly the corticomotor neuronal system, crucial for independent fine finger movements.27 Furthermore, the Ice Age engraver had to employ both hands for the task, one to hold the ivory, the other to manipulate the engraving tool, signifying skilled bimanual interactions. All these visual and motor factors incidentally preclude any possibility of random scratching or doodling28; great skill and dexterity would have been required for a very time-consuming task taking many hours.

The ice age honeycomb engraving affirms ‘the arrival of the modern brain’

Famous wall paintings, such as those in the caves of Chauvet and dated as far back as around 35 000 years ago, as with many of the objects displayed in the British Museum exhibition, leave no doubt that Ice Age people, anatomically the same as us, were consummate representational artists. But an image such as that engraved on the Eliseevitchi ivory demonstrates something more: these people were equally skilled at creating seemingly abstract images. It may not be too speculative, therefore, to suggest that the brain of prehistoric man over 20 000 years ago in terms of its conceptual, creative and artistic abilities was remarkably similar to our own. How apt, therefore, that the exhibition ‘Ice Age art’ was subtitled ‘the arrival of the modern mind’, a subtitle which in the artistic context here could justly be modified to ‘the arrival of the modern brain’.

Acknowledgments

GDS is most grateful to Dr Jill Cook, Deputy Keeper, Department of Prehistory and Europe at the British Museum, for her invaluable help and critical comments.

References

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Footnotes

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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