Serra da Capivara National Park covers 129,140 hectares — roughly 1,290 square kilometres — of southeastern Piaui, spilling across the municipalities of Sao Raimundo Nonato, Sao Joao do Piaui, Coronel Jose Dias and Canto do Buriti. The name means Capybara Hills, though the range is less a mountain chain than a shattered plateau: sandstone escarpments cut by steep box canyons the locals call boqueiroes, their walls overhung just enough to shelter a fire, a family, a wall of paintings.\n\nThe vegetation is caatinga, the thorny dry forest of the Brazilian interior, shading into cerrado at the margins. For most of the year it looks dead — grey sticks, bare branches, a landscape of splinters. Then the rains come and the whole thing turns green within days. The dryness is what preserved the art. Rock shelters that stay bone-dry for eleven months of the year make excellent archives.

More than a thousand archaeological sites have been recorded inside the park boundaries, and researchers keep finding more. The paintings belong to what Brazilian archaeologists call the Nordeste tradition, one of a set of regional rock-art styles catalogued across the country alongside the Agreste, Sao Francisco and Planalto traditions.\n\nWhat sets the Nordeste panels apart is that they tell stories. Elsewhere in the world, prehistoric painters left animals in isolation, or handprints, or abstractions. Here the figures interact. There are hunting parties, skirmishes, dances, scenes of sex, small crowds gathered around something that may be a birth or a ritual. Red deer appear more often than any other animal. The pigments are mostly ochre in several shades of red, with occasional yellow limonite and grey. Hundreds of the paintings have been dated to around twelve thousand years before the present; a number of researchers argue for considerably older, and that argument has never been settled.

The park exists because Niede Guidon went looking. A Brazilian archaeologist trained at the Sorbonne, she began working in southeastern Piaui in 1973 with a joint Brazilian-French team. What she found convinced her the region needed protection more than it needed excavation. In 1978 she petitioned the federal government; on 5 June 1979 Serra da Capivara National Park was created.\n\nTwelve years later, in 1991, UNESCO inscribed it as a World Heritage Site under criterion iii — outstanding testimony to a cultural tradition. Guidon served as the park's head archaeologist and spent the rest of her working life there. Its most famous site, the rock shelter called Boqueirao da Pedra Furada, is also its most contentious: the dates Guidon claimed for the charcoal and stone found there would push human arrival in the Americas back by tens of thousands of years, and that claim remains disputed.

The park's bearded capuchins have what primatologists describe as the largest known tool kit of any wild capuchin population. They use stones for cracking food open, for threat displays and in sexual display. They probe with sticks. On the ground they loosen soil with a stone and then dig with their hands for roots and arthropods. Archaeologists working in the park have traced capuchin stone-tool use back at least three thousand years — which makes the monkeys, in a strict sense, an archaeological culture of their own.\n\nThis is not a charming aside. Capuchins smashing stone against stone produce sharp flakes that look a great deal like the simplest human tools, and that resemblance sits squarely in the middle of the argument over what the oldest layers at Pedra Furada actually contain.

Sao Raimundo Nonato, the town at the park's gate, sits about 576 kilometres from Teresina. A regional airport opened there in 2015, which helped, but the park has never drawn the crowds its significance would suggest — 12,238 visitors in 2021, a rounding error next to what a comparable site in Europe would receive in a week.\n\nMoney has been the chronic problem. In August 2016 the park closed temporarily when funding ran short. In early 2017 a shared management arrangement took effect, putting the Museum of the American Man Foundation alongside ICMBio and the heritage institute IPHAN on a permanent monitoring committee. It is an unusual model, born of necessity: a place this remote, this fragile and this important has never been able to rely on a single source of support.