When, in 1879, Don Marcelino Sanz de Sautuola discovered the astonishing paintings of bison in his cave at Altamira, his claim that they were of prehistoric origin was ridiculed. The breathtakingly accomplished images were impossible to square with the prevailing image of Ice Age ‘savages’, and he died discredited as a hoaxer.

In the century since the cave art of the Palaeolithic has been accepted as genuine, it’s suffered the opposite fate. It’s clearly so important a clue to the origins of human culture that interpreting it has come to involve impossibly weighty questions. Does it reveal the first human religion and, if so, what was it? Was it an individual or communal enterprise? Was it devotional, ritual, practical, or ‘simply decorative’ (whatever that may mean)? Does it locate the roots of human culture in totemism, or sympathetic magic, or initiation rites? The cumulative effect of all the grand theories in the first half of the twentieth century was to turn the cave paintings into a kind of Rorschach ink blot test, where every theorist saw their own version of human genesis revealed.

Structuralism was the last grand attempt at a definitive decoding of cave art, but its overarching theory that the paintings mediated binary oppositions left many specifics and anomalies unaccounted for. Since then, scholars have tended to fight shy of the big questions, and limit their researches to accumulating ever more detailed analyses of paint scrapings and cross-hatching techniques. But David Lewis-Williams has had enough of this. In his view, either there’s now enough evidence to interpret the images, or else there’s never going to be enough. In either case, it’s time to attempt another big theory, one which he compares in scope to Darwin’s: not a closed, provable theorem but an explanatory framework which accounts for multiple unrelated phenomena and opens up scope for further discovery. Those familiar with his previous work on African San (‘Bushman’) rock art and altered states of consciousness will have some idea of his basic trajectory, but in The Mind in the Cave he travels further and deeper.

Lewis-Williams sets about his task in brusque, no-nonsense fashion. His strategy is to build a scaffolding of parallel, intertwined arguments, drawing together neurobiology, contemporary hunter-gatherer rock art and the environmental and social conditions of Ice Age Europe, and see what shape emerges from the salient facts. The result is a dense but well-organised book which mounts a closely-argued, original and compelling case.

The first building-block of his argument is consciousness: we have little idea of the culture and society which produced the cave art, but we are certainly dealing with humans with anatomically modern brains generating a symbolic culture. In his view, most theories of how human intelligence developed place too much emphasis on the functions of reason and problem-solving, which only became privileged in our culture within the last few centuries. There is, he maintains, a broad spectrum of consciousness, of which active reasoning represents only one end. Other parts of the spectrum are visited by all humans in hypnagogia, sleep and dreams – and are also specifically cultivated in modern rock-art-making societies through ‘shamanic’ techniques like sensory driving with drumming and dancing, fasting, drugs, hyperventilation and sensory deprivation (in, for example, dark caves). Here, Lewis-Williams draws on his own previous work, and also that of cognitive psychologists like Heinrich Klüver and Ronald Siegel and anthropologists like Gerardo Reichel-Dolmatoff, who have cumulatively demonstrated that, in such altered states, the same visual and sensory phenomena are generated both in the lab and in the field.

The ‘hallucinations’ experienced in altered states divide into two distinct stages. The first include closed-eye patterns, phosphenes and form-constants which, as Lewis-Williams has previously shown, map closely onto both San and Palaeolithic cave art. These evolve into a second stage of visions, which present iconic and symbolic content. The first stage is neurologically based and identical across all cultures; the second, crucially, is interpreted differently in different cultures. Besides posing serious problems for the Jungian assertion that ‘archetypes’ are culturally universal, this analysis also suggests that cave art may be a depiction not of real objects but of patterns and visions ‘seen’ on the rock walls in altered states of consciousness and depicted according to a pre-existing cultural scheme.

But what was this pre-existing scheme? This is the big question: what was it which prompted the entire package of cave art, figurative carving, body-painting, ritual burial and the rest to emerge in Europe around 40,000 years ago? Lewis-Williams points out that it didn’t: some symbolic carvings in Africa date back to at least 30,000 years before the European ‘symbolic revolution’. The reason for the explosion of symbolic culture in Ice Age Europe, in his view, was the co-existence of humans and Neanderthals. The archaeological evidence of Neanderthal culture is strikingly lacking in precisely these kinds of symbolic artefacts, suggesting that although Neanderthals had dreams, visions and language, they lacked the component of consciousness which would have enabled them to recall them, share them, socialise them and represent them. The profusion of cave art, then, suggests that human symbolic culture received a defining boost because it was precisely this part of the spectrum of consciousness which differentiated humans from their Neanderthal neighbours. Cave art was part of a technology which enabled humans, uniquely, to communicate their dreams, and to inhabit an imaginatively shared spirit world. If this is true, we perhaps have the Neanderthals to thank (or blame) for setting humanity on the cultural trajectory towards modern civilisation.

Drawing judiciously on parallels with contemporary San and North American rock art, Lewis-Williams begins at this point to sketch out how this spirit world might have been configured. He suggests that the underlying similarities of different ‘shamanisms’ around the globe have a neurological basis: the same trance states generate the same cosmology, for example the belief in an ‘underworld’ from which dreams and visions emerge. In the light of this, he proposes a network of varied Palaeolithic ‘shamanisms’ with some underlying similarities. Caves were associated with the spirit world; cave walls were the membrane between the two worlds. Images of dots and handprints suggest that there were ritual techniques for merging into the membrane and bridging the worlds. The many paintings which follow contours or fissures in the rock walls suggest that the image, perhaps already captured in trance or dream, was ‘recognised’ in the wall and then enhanced. The faint tallow lamps carried into the depths would have meant that walls were explored slowly and in miniature scale, as much by touch as by sight. While the art in large chambers near ground level may have been communal, turning the caves into shared ritual spaces, deep diverticules and passages would have been painted by solitary ‘vision-questers’. The lines piercing many of the figures, traditionally read as ‘spears’ or ‘arrows’, are more likely to represent, as they do in San rock art, the numinous buzzes and flashes associated with trance states. The key to all this is that cave art wasn’t intended to reproduce the real world of daylight outside: it represented things which had already been seen, but only as mental imagery. The process of ‘fixing’ it on the walls was, due to its physical difficulty, probably not attempted in altered states of consciousness, but presented as evidence of spirit journeys previously undertaken.

The question of meaning in cave art will always be problematic: we’re attempting within our own cultural framework to make sense of something which played a role in a very different one. There are many possible ways of approaching it, and they aren’t mutually exclusive. Lewis-Williams is careful to stress that what he’s offering is not a proof but an explanatory grid, which can be judged by how useful it is and how good it is at predicting future discoveries. He has begun with the most basic building-blocks, and successfully modelled an interpretative system. His model is conservative in some ways, relying heavily on mechanistic reductions of the shamanic cosmos to the neurology of consciousness: no psychedelic flights of fancy here. But in other ways it’s radically mind-expanding, locating the origins of symbolic culture in caves of the mind far away from what we now think of as modern human intelligence. Its strength is that it’s open-ended, providing a robust superstructure for further work, notably for the multidisciplinary theories of acoustic, shamanic and psychotropic dimensions of prehistoric culture which have tended to be marginalised in the academic discourse. And while it significantly advances the process of making sense of Palaeolithic cave art, it does nothing to rob it of its eternal strangeness.