From the earliest times, humans across the world have made homes in caves. ‘We know that Stone Age cave visitors carried light into the dark zones of caves and, on every continent except Antarctica, left evidence of their visits in the form of images on the rock walls,’ says Lisa Fletcher, co-author of Cave: Nature and Culture, which is forthcoming in May.
Cave dwellers never ventured too deeply into their homes. There is no archaeological evidence that humans ever lived deep within cave systems, according to Fletcher. ‘Subterranean colonies are the stuff of fantasy and science fiction,’ she says. ‘Humans have used the entrances of caves for shelter, animal husbandry, storage, and so on for hundreds of thousands of years.’
‘We can only speculate what induced early humans to venture into the absolute darkness, but perhaps their motives were not dissimilar to those of today’s cave explorers,’ says Ralph Crane, who co-authored Cave with Fletcher.
‘We both love Eamon Grennan’s poem The Cave Painters, which is a meditation on this very topic and pictures early humans venturing “deeper into the dark” until they stand in “an enormous womb of / flickering light and darklight”,’ he says.
Prehistoric visitors have left traces other than paintings for modern spelunkers to discover. In the 1970s, 274 distinct human footprints left by nine individuals were found in Jaguar Cave, Tennessee, proving that the cave had been explored 5,400 years earlier.
‘Caves are found on every continent, if we include the ice caves of Antarctica,’ says Crane. ‘Usually though, when people talk about caves, they are thinking of solution caves, created through the dissolution of bedrock, mostly limestone, but also dolomite and other forms of rock.’
Lava flow and coastal erosion also form caves, although most are found in karst areas that form around 15 per cent of the planet’s surface. A karst landscape is made up of water soluble rocks, such as limestone, dolomite and gypsum.
‘There are huge numbers of caves, in Central and South America, in Europe and Asia, and in Australasia, but fewer in Africa,’ says Fletcher.
The majority of caves in continental North America – including the world’s largest, Mammoth Cave in Kentucky – are found in limestone karst. Hawaii is the exception. ‘The most common caves found there are lava tubes, formed during the cooling of the lava,’ says Fletcher.
‘We live in Tasmania, where more caves are found than anywhere in Australia. In the south of the state, Newdegate Cave – the state’s largest show cave – is a rarity because it is formed in dolomite, rather than limestone,’ she adds.
Once humans left cave systems they were slow to return, even for brief visits. Caving for pleasure, sport, and science took off in the second half of the 19th century. Technological advances in after the Second World War made caving safer, and opened the sport up to more people.
‘Probably the most important figure in the history of caving is the Frenchman Édouard-Alfred Martel,’ says Crane. His achievements included the first underground crossing of the Plateau de Camprieu in southern France in 1888 and the first descent of Gaping Ghyll, Yorkshire, the deepest cave shaft in Britain.
Although the return to caves is a relatively new phenomenon, caves have always had a significant role in culture. ‘There are literal and metaphorical caves everywhere in literature and film – from Homer’s Odyssey, through Shakespeare, to Michael Ondaatje’s The English Patient, from Billy Wilder’s cult classic, Ace in the Hole, to a spate of recent horror films including The Cave, The Descent, and Sanctum,’ says Fletcher.
Hollywood aside, Fletcher and Crane take Coleridge’s Kubla Khan as the touchstone for thinking about caves. ‘The lines “Through caverns measureless to man / Down to a sunless sea” echo through fictional and non-fictional subterranean stories on both page and screen,’ says Fletcher.
‘Literature frequently turns to caves for symbols and metaphors to help understand the human condition above ground,’ says Crane. ‘Over and again caves are wombs and tombs, they are dens for thieves, gates to the underworld, and symbols for the dark recesses of the soul.’
There’s life in the darkness, too. ‘The earliest attempts to classify cave biology identified darkness as the distinguishing feature of the habitat. From a human perspective, the most obvious and abundant life in caves exists in the entrance zone where there is more light,’ says Fletcher. ‘Moving deeper into a cave, through the layers of darkness, the conditions for life as we know it become more difficult and evidence of cave biology diminishes.’ For expert speleobiologists, the dark zone, which appears devoid of life to most of us, offers unlimited opportunities to discover new species.