Monte Sierpe, the "Band of Holes"

The band varies from 14 to 22 m wide, averaging about 19 m. It is divided into at least 60 sections, separated by empty strips wide enough to cross, and differing in hole count and in whether the holes have stone walls. The holes are dug into colluvial and probably wind-blown sediment on the hillside⁠[1].

The Chincha Kingdom controlled the Chincha and Pisco valleys in the Late Intermediate Period (AD 1000 to 1400), with a population that colonial records suggest exceeded 100,000 and specialist farmers, fisherfolk and merchants. The Inca absorbed it in the 15th century and reorganised tribute on a decimal system⁠[1]. The site lies in the chaupiyunga, the transitional zone between coast and highlands where groups met to trade, near routes linking the highlands to the Pacific⁠[5].

Mapping with a DJI Mavic 3E drone and a high-accuracy GNSS receiver confirmed about 5200 holes. In one section at least nine consecutive rows hold eight holes each; in another, six rows of seven and one of eight make 50; in a third, at least 12 rows alternate between seven and eight⁠[1].

Late Intermediate Period pottery was found on the band and Chincha and Inca pottery in the nearby settlement. Charcoal from inside hole 1905-01 gave 635 ± 15 BP (UCIAMS-223236), AD 1320 to 1405 at 95.4% on the ShCal20 curve⁠[1].

Sediment from 19 holes and two controls outside the band contained at least 27 pollen types. Maize pollen, which travels little, appears in at least six samples; willow and bulrush, used for baskets and mats, are nearly everywhere. Starch of squash and amaranth and maize phytoliths were also found. The controls had no phytoliths, but one held squash starch. Citrus pollen in two low holes shows some colonial-era input⁠[1].

The holes were made by people and used in the late pre-Hispanic centuries. One radiocarbon date and the surface pottery place use in the Late Intermediate Period and the Inca era; when the band was first dug is not known⁠[1].

The layout is regular within sections, which rules out casual digging and suggests counting. The microbotanical evidence fits plants carried into the holes in baskets or bundles, not plants growing there: there is no rain at this altitude and no groundwater on the slope, and the brief fog oases could not have watered maize⁠[1].

There are no human remains apart from a few intrusive tombs at the south end, no ore, no slingstones or other signs of fighting, and no non-local goods so far⁠[1].

Market and accounting. The 2025 team proposes that Chincha communities used the band as a barter marketplace where goods placed in holes could be seen and counted, and that under the Inca it became a place to collect and account for tribute, each section perhaps tied to a social group. They compare the layout with a khipu from near Pisco (Berlin, VA 16135) whose cords fall into 80 groups of 10, 11 or 12⁠[1]⁠[6]. A grid of squares on storeroom floors at the Inca site of Inkawasi offers a parallel for counting produce on the ground⁠[7].

Storage. John Hyslop suggested the holes stored goods along the Inca road⁠[3]. Storage predicts roofing or sealing, and a single use rather than a counting layout; the new data are consistent with goods in the holes but do not test duration⁠[1].

Defence, water or fog capture, gardens, burial and mining all fail one or more tests: no weapons or fortification, no water source for crops, no burials and no ore. A geoglyph is not ruled out⁠[1].

Test excavations through holes in several sections, with more radiocarbon dates on short-lived material from the base of the fills, would date the band's construction and show whether sections were built at different times. The authors plan such work and ask whether the band was a "landscape khipu"⁠[1]⁠[8].

A formal comparison of the full hole-count map with the open khipu corpus, against randomised layouts, would test whether the numerical patterns go beyond what any regular digging produces⁠[9]. Sediment samples taken in a grid, with more controls outside the band, would show whether crop pollen is concentrated in particular sections, as an accounting system by group would predict.