SAN CRISTOBAL DE RAPAZ, Peru – The route to this village 3,960 meters above sea level runs from the desert coast up hairpin bends, delivering the mix of exaltation and terror that Andean roads often provide. Condors soar above mist-shrouded crags. Quechua-speaking herders squint at strangers who arrive gasping in the thin air.

Rapaz’s isolation has allowed it to guard an enduring archaeological mystery: a collection of khipus, the cryptic woven knots that may explain how the Incas – in contrast to contemporaries in the Ottoman Empire and China’s Ming dynasty – ruled a vast, administratively complex empire without a written language.

Archaeologists say the Incas, brought down by the Spanish conquest, used khipus – strands of woollen cords made from the hair of animals like llamas or alpacas – as an alternative to writing. The practice may have allowed them to share information from what is now southern Colombia to northern Chile.

Few of the world’s so-called lost writings have proved as daunting to decipher as khipus, scholars say, with chroniclers from the outset of colonial rule bewildered by their inability to crack the code. Researchers at Harvard have been using databases and mathematical models in recent efforts to understand the khipu (pronounced KEE-poo), which means knot in Quechua, the Inca language still spoken by millions in the Andes.

Only about 600 khipus are thought to survive. Collectors spirited many away from Peru decades ago, including a mother lode of about 300 held at Berlin’s Ethnological Museum. Most were thought to have been destroyed after Spanish officials decreed them to be idolatrous in 1583.

But Rapaz, home to about 500 people who subsist by herding llamas and cattle and farming crops like rye, offers a rare glimpse into the role of khipus during the Inca Empire and long afterward. The village houses one of the last known khipu collections still in ritual use.

Even here, no one claims to understand the knowledge encoded in the village’s khipus, which are guarded in a ceremonial house called a Kaha Wayi. The khipus’ intricate braids are decorated with knots and tiny figurines, some of which hold even tinier bags filled with coca leaves.

The ability of Rapacinos, as the villagers are called, to decipher their khipus seems to have faded with elders who died long ago, though scholars say the village’s use of khipus may have continued into the 19th century. Testing tends to show dates for Rapaz’s khipus that are well beyond the vanquishing of the Incas, and experts say they differ greatly from Inca-designed khipus.
Even now, Rapacinos conduct rituals in the Kaha Wayi beside their khipus, as described by Frank Salomon, an anthropologist at the University of Wisconsin who led a recent project to help Rapaz protect its khipus in an earthquake-resistant casing.

One tradition requires the villagers to murmur invocations during the bone-chilling night to the deified mountains surrounding Rapaz, asking for the clouds to let forth rain. Then they peer into burning llama fat and read how its sparks fly, before sacrificing a guinea pig and nestling it in a hole with flowers and coca.

The survival of such rituals, and of Rapaz’s khipus, testifies to the village’s resilience after centuries of hardship. Fading murals on the walls of Rapaz’s colonial church depict devils pulling Indians into the flames of hell for their sins. Feudal landholding families forced the ancestors of many here into coerced labour.

Rapacinos have also faced more recent challenges. A government of leftist military officers in the 1970s created economic havoc with nationalization, sowing chaos exploited by the Maoist guerrillas of the Shining Path who terrorized Rapaz into the 1990s, effectively shutting it off from significant contact with the rest of Peru.

Throughout it all, perhaps because of the village’s high level of cohesion and communal ownership of land and herds, Rapacinos somehow preserved their khipus in their Kaha Wayi.

Far from Rapaz, the pursuit to decipher khipus faces its own challenges, even as new discoveries suggest that they were used in Andean societies long before the Inca Empire emerged as a power in the 15th century.

Scholars say they lack the equivalent for khipus of a Rosetta Stone, the granite slab whose engravings in Greek were used to decipher ancient Egyptian hieroglyphics. Jesuit manuscripts discovered in Naples, Italy, had seemed to achieve something similar for khipus, but are now thought to be forgeries.