There are thousands of lined holes in Peru. Researchers think they finally know why

In South America, a mysterious monument stretches nearly a mile (1.5 kilometers) across the southern Peruvian Andes. Called Monte Sierpe, meaning snake mountain, it consists of rows of around 5,200 stacked holes, and researchers have put forward a new theory about what they might have been.

In a study published today in the journal Antiquity, an international team of researchers performed sediment analysis and drone photography of Monte Sierpe. Their results suggest that the monument, also known as the ‘Strip of Holes’, was used by local peoples in accounting and trade.

« Hypotheses about the purpose of Monte Sierpe range from defense, storage and reporting to water collection, fog trapping and horticulture, » Jacob Bongers, an archaeologist at the University of Sydney and lead author of the study, told Antiquity in a statement. « The function of the site remains unclear. »

Holes full of corn

The holes are arranged in sections and each hole is 3.3 to 6.6 feet (1 to 2 meters) wide and 1.6 to 3.3 feet (0.5 to 1 meter) deep. The team shed light on the puzzling monument at both the micro and macro levels by performing microbotanical analysis of the burrow sediments and capturing high-resolution aerial images. Microbotanical analysis revealed plant remains such as maize as well as wild plants traditionally used in basket making.

« These data support the hypothesis that during pre-Hispanic times local groups periodically lined the holes with plant material and deposited goods inside them using woven baskets and/or bundles for transport, » explained Bongers.

Moreover, the aerial images suggest that the placement of the holes is consistent with the digital models. The researchers argue that this, in addition to its segmented organization, makes Monte Sierpe like a giant khipu: a rope and knot documentation system used by Andean people. As such, Monte Sierpe may have been a giant accounting system that the Inca state used to collect taxes.

Bartering and accounting

The Incas were a pre-Columbian indigenous civilization, best known for building Machu Picchu (recently admired for this three-walled building), whose modern descendants are the Quechua-speaking people of the Andes. Monte Sierpe would have been conveniently located between two Inca administrative sites and near an intersection of pre-Hispanic roads. Moreover, it also lies between the mountains and the lower coastal plain, an area where communities from both regions would have gathered for trade.

In general, researchers suggest that the pre-Inca kingdom of Chincha originally developed and used Monte Sierpe for controlled trade, which then became the Inca’s place of accounting.

« This study contributes to an important case from the Andes of how past communities changed past landscapes to bring people together and encourage interaction, » Bongers concluded. « Our findings expand our understanding of barter markets and the origins and diversity of local accounting practices in and beyond the ancient Andes. »