Mysterious ancient holes in Peru puzzling researchers for decades

A series of about 5,200 holes stretching nearly 1.5 kilometers along the Pisco Valley in the Southern Andes of Peru has puzzled researchers for nearly a century, CE Report quotes Kosova Press.

But a new look at Monte Sierpe, or "Snake Mountain," may help archaeologists decipher why ancient people built it hundreds of years ago.

The "hole group," as it is unofficially called, first attracted attention when National Geographic published aerial photos in 1933.

Hypotheses about the purpose of the holes have included defense, accounting, storage, gardening, water collection, and fog capture.

Now, new drone images and an analysis of pollen grains found inside the holes are leading researchers to suggest that the site originally served as a bustling market for a pre-Inca civilization and later as a method of accounting for the Inca, according to a study published in Antiquity.

"Why would ancient peoples make over 5,000 holes in the hills of southern Peru?" said the lead author of the study, Jacob Bongers, an archaeologist at the University of Sydney and a researcher at the Australian Museum Research Institute.

"We don't know exactly why they are here, but we have gathered some promising new data that provides important insights and supports new theories about the site's use," Bongers said.

Each hole has a width of 1 to 2 meters and a depth of 0.5 to 1 meter. Drone photography shows that they are organized into about 60 distinct sections separated by empty spaces.

Bongers' team was also able to identify patterns, such as a section with 12 rows alternating between seven and eight holes, suggesting that the arrangement is not random.

Ancient pollen grains found inside the holes show the presence of crops like corn, as well as wild plants, including reeds and bulrushes, which were traditionally used to make baskets.

Crops and other goods may have been placed in these baskets or stored in the holes, which could have been lined with plant material. It is also possible that structures were built over or near the holes, Bongers added, but there is no evidence that any architecture ever existed.

The team believes that the indigenous people of the pre-Inca Chincha Kingdom, from Peru’s coast and mountains, may have come to trade goods and exchange using their goods rather than currency.

The dating of the holes suggests that the site was used between 600 and 700 years ago, according to KosovaPress.

While the team is still conducting further radiocarbon dating to determine an exact timeframe, they believe the site was built during the Late Intermediate Period of Peru, between 1000 and 1400 AD, which aligns with the use of the site by the pre-Inca civilization.

Pollen from citrus plants, brought to the region during the colonial period between 1531 and 1825, suggests that the site was still in use after the fall of the Inca Empire in 1532, when the Spanish colonized Peru. It was likely abandoned eventually "because the Spanish could not find a way to integrate the site into their economic expansion," Bongers said.

It is possible that Monte Sierpe only included a few sections of holes as a trading site before expanding under the Inca Empire, or it may have been abandoned before the Incas arrived. Either way, the team believes the Inca used the site as a large-scale accounting device.