Indigenous Accounting : Monte Sierpe

 Monte Sierpe, also known as the 'Band of Holes,' is a unique archaeological feature located in the Pisco Valley, Peru. The sources provide a detailed physical Description of the site and establish its Chronology within the Late Intermediate Period and Late Horizon, placing it in the larger context of Indigenous accounting and exchange.

Description of Monte Sierpe

Location and Naming Monte Sierpe ('Serpent Mountain') is located on the north side of the Pisco Valley in the coastal desert zone of southern Peru, situated approximately 35km from the Pacific coastline. The site is positioned in the chaupiyunga, a transitional ecological area between the highland valleys and the coastal plain. This strategic placement is near the intersection of pre-Hispanic roads and one of the most important pre-Hispanic coast-highland trade routes. It is situated between two Inca administrative centers: Tambo Colorado and Lima La Vieja. The name ‘Monte Sierpe’ holds historical continuity, as a "famous wine hacienda" bearing that name existed in the valley of Humay in the eighteenth century.

The existence of the 'Band of Holes' was initially brought to wider attention in 1933 when the National Geographic Society published Robert Shippee’s aerial photographs of the aligned depressions.

Physical Features and Structure Monte Sierpe is described as an artificial earthen band that follows a ridge, stretching for 1.5km from the valley bottom up the side of a hill. It is a unique architectural form in the pre-Hispanic Andes.

Key descriptive features include:

• Hole Count: The site consists of approximately 5200 precisely aligned holes.
• Dimensions: The width of the band averages around 19m, varying between 14 and 22m. The individual holes are typically 1–2m in diameter and 0.5–1m in depth.
• Construction: The holes are excavated out of natural and mounded sediments, and some are partially lined with stone walls.
• Segmentation: The band is not continuous but is segmented into sections or blocks. Researchers identified at least 60 distinct sections. These sections are separated by empty spaces, which likely functioned as ‘crosswalks’ to allow east–west movement across the site.

Numerical Patterning High-resolution drone imagery revealed distinctive patterns in hole count across various sections, suggesting an underlying intention in the structural organization. This numerical patterning is a significant insight into the site’s organization and use. Examples of these patterns include:

• Section 'a' having at least nine consecutive rows with eight holes each.
• Section 'b' having six consecutive rows with seven holes and one row with eight holes, totaling 50 holes.
• Section 'c' exhibiting alternation between counts of seven and eight holes across at least 12 rows. The segmented and regular arrangement of the holes is structurally reminiscent of at least one complex Inca-style khipu (knotted-string device) found near Pisco, suggesting a potentially similar purpose for counting and sorting.

Chronology of Monte Sierpe

The sources indicate that Monte Sierpe was constructed and used across the Late Intermediate Period and the Late Horizon.

Dating Evidence

• Periods of Use: The site is thought to date to at least the Late Intermediate Period (AD 1000–1400) and continued in use through the Late Horizon (Inca Period, AD 1400–1532).
• Pottery Fragments: The recovery of Late Intermediate Period- and Late Horizon-style pottery fragments from the surface confirms that the site was constructed during the Late Intermediate Period and used through the Late Horizon.
• Radiocarbon Dating: Charcoal collected from inside one of the holes (1905-01) yielded a radiocarbon date of 635±15 BP, which calibrates to AD 1320–1405 at 95.4% probability. This dating is consistent with the chronology of nearby defensive settlements, which are also Late Intermediate Period and Late Horizon in date.

Chronological Shifts in Function The chronological context supports a proposed functional shift for Monte Sierpe, tied to the political transitions of the Pisco Valley region:

1. Late Intermediate Period (Chincha Kingdom): The Chincha Kingdom, a wealthy polity, controlled the area during this time. The sources propose that Monte Sierpe originally functioned as a barter marketplace under the Chincha Kingdom. This function aligns with the Chincha society's burgeoning population, economic specialization (fisherfolk, farmers, merchants), and agricultural surplus.
2. Late Horizon (Inca State): Following the Inca conquest in the fifteenth century, the Chincha Kingdom was incorporated into the Inca state. The site may have been adapted to serve the Inca economic system, functioning as an accounting device for tribute collection and redistribution. In this interpretation, each section of holes could have corresponded to a specific social group for tax payment, reflecting the Inca mit’a system and decimal administration.

Possible Colonial-Era Presence While the primary use is considered pre-Hispanic, the microbotanical analysis indicates the identification of certain pollens introduced during the Colonial-era (AD 1532–1825), such as Citrus, in two holes at the southern end. Other wind-borne colonial-era introductions, such as Syzygium and Carya, were also identified. However, there is no documentary evidence for subsequent use of the site during the Colonial period.

Monte Sierpe's shift from a localized Chincha barter market to an integrated Inca accounting device demonstrates how a unique built environment—the $1.5\text{km}$-long band of holes—was repurposed across different political eras to manage the flow of goods and resources in the Pisco Valley.

The recent investigation into Monte Sierpe utilized a multi-disciplinary approach, combining advanced remote sensing technology with detailed archaeobotanical and chronological analysis to address the long-standing uncertainty regarding the function of the 'Band of Holes'. The sources detail the research goals and the rigorous methodologies employed to interpret this unique pre-Hispanic Andean construction.

Goals and Context of the Research

The research builds upon previous studies (Wallace 1971; Hyslop 1984; Engel 2010; Stanish & Tantaleán 2015). The primary objectives of the current study were twofold: to document the layout of Monte Sierpe in greater detail than previously achieved and to test the hypothesis proposed by Hyslop (1984: 289) that the site was used for storing goods.

Crucially, the authors aimed to use clear archaeological evidence and reasoning to challenge pseudo-archaeological narratives, such as those associated with ‘ancient astronaut’ ideology, which have gained prominence in popular media surrounding the site. By integrating new data, the researchers proposed that Monte Sierpe functioned as a local, Indigenous system of accounting and exchange.

Methodologies Employed

1. High-Resolution Mapping and Layout Documentation

To document the layout and determine the precise number and arrangement of the holes, the researchers employed advanced aerial surveying techniques:

• Equipment: Mapping was conducted using a DJI Mavic 3E drone.
• Positioning System: The high-accuracy (20–40mm) Trimble Catalyst global navigation satellite system (GNSS) was used.
• Analysis: The resulting high-resolution drone imagery and digital elevation model documented approximately 5200 holes and, critically, revealed distinctive numerical patterns in hole counts across various sections. This documentation of structural organization was key to suggesting parallels with Andean record-keeping devices like the khipu.

2. Chronological Dating

To establish the period of construction and use, the researchers relied on ceramic typology and radiocarbon dating:

• Ceramics: The recovery of Late Intermediate Period- and Late Horizon-style pottery fragments from the surface of Monte Sierpe indicated that the site was constructed during the Late Intermediate Period (AD 1000–1400) and remained in use through the Late Horizon (Inca Period, AD 1400–1532).
• Radiocarbon Dating: Charcoal collected from inside one hole (1905-01) was submitted for dating.
• Calibration: The date was obtained from the Keck-CCAMS Facility at the University of California Irvine (UCIAMS) and modeled using OxCal v.4.4 and the SHCal20 Southern Hemisphere calibration curve.
• Result: The resulting date of 635±15 BP calibrated to AD 1320–1405, confirming the site's use during the Late Intermediate Period.

3. Microbotanical and Sediment Analysis

To investigate the contents and purpose of the holes, sediment samples were subjected to microbotanical analysis:

• Sampling Strategy: Sediment was opportunistically sampled from 19 holes across the site and at different elevations, along with two control samples (C7 and C10) collected 5–8m outside the band, for a total of 21 samples. The top 50mm of sediment was removed before sampling.
• Microfossil Targets: Samples were analyzed for the presence of pollen, phytoliths, and starch grains. The analysis also identified diatoms, sponge spicules, and spores.
• Laboratory Analysis: Analysis was conducted at the Archaeobotanical and Paleoecological Laboratory at the University of South Florida and the Laboratorio de Palinología y Paleobotánica at the Universidad Peruana Cayetano Heredia in Peru.
• Results and Interpretation:
  • The recovery of maize (pollen, phytoliths) and Cucurbita (starch grains) supported the idea that pre-Hispanic food crops were present.
  • The presence of heavy, insect-borne pollens (e.g., Salix, Convolvulaceae, Malvaceae) suggests human transmission into the site, as opposed to natural wind distribution.
  • The ubiquitous presence of Typha (bulrush) pollen, which typically travels short distances, was interpreted as evidence that the holes were periodically lined with plant materials or that bundled goods (carried in baskets or mats woven from bulrushes) were moved to and from the site.

Methodology's Contribution to Interpretation

The combined methodologies led the researchers to reject previous hypotheses concerning defense, mining, or water collection, and strongly supported the interpretation of Monte Sierpe as a localized system for managing resources. The detailed mapping revealed intentional structural organization that mirrors numerical systems used by Andean communities (like khipus), while the microbotanical evidence confirmed the deliberate placement of economic and industrial plants in the holes during pre-Hispanic times.

The research is presented as contributing valuable data to broader discussions on Indigenous numeracy, mathematical practices, and resource management strategies. The authors conclude by outlining plans for future research, including test excavations, additional radiocarbon dating, and the study of more local khipus, which are necessary for further evaluating their proposed model.

The approach taken at Monte Sierpe—using advanced imaging to document structure and micro-analysis to identify contents—is like using a magnifying glass to read a library catalogue; the layout confirms it is a system for organization, while the residue confirms what was being organized (goods and crops), leading to the conclusion that the structure was an accounting tool rather than merely storage.

The sources propose that Monte Sierpe functioned as a localized, Indigenous system of accounting and exchange. This interpretation is based on new structural analysis, microbotanical evidence, and the site’s strategic location, leading the authors to reject earlier hypotheses concerning defense, mining, or water collection.

The functional hypothesis outlines a chronological shift in the site's role, adapting to the successive political control of the region: initially serving as a barter marketplace under the Chincha Kingdom during the Late Intermediate Period, and later as an accounting device for tribute collection under the Inca during the Late Horizon.

Structural and Physical Evidence Supporting Accounting

The organization and contents of the site strongly support its proposed function as a mechanism for managing resources:

• Numerical Patterning: Detailed drone imagery revealed approximately 5200 holes which cluster into multiple sections or blocks. The documentation showed distinctive patterns in hole count across various sections, suggesting an underlying intention in the structural organization.
• Khipu Analogues: The segmented and regular arrangement of the holes is considered structurally reminiscent of complex Inca-style khipus (knotted-string devices) used for detailed record-keeping, such as one excavated near Pisco. This suggests a parallel purpose for counting and sorting. Furthermore, a complex Inca-style khipu found near Pisco has pendant cords arranged in distinct groups of similar size, exhibiting intricate arithmetic interrelationships characteristic of "working" accounting operations that would have occurred at Monte Sierpe.
• Microbotanical Evidence: Sediment analysis confirmed the presence of pre-Hispanic economic and industrial crops, most notably maize and Cucurbita (squash/gourd). The identification of heavy, insect-borne pollens (like Salix or Humboldt’s willow) and self-pollinating maize pollen suggests human transmission of these materials into the holes.
• Transport and Lining: The ubiquitous presence of Typha (bulrush) pollen suggests that the holes may have been periodically lined with plant materials or that bundled goods were moved to and from them, as baskets and mats were historically woven from bulrushes for transport and storage in the Chincha region.

Monte Sierpe as a Node of Exchange

The location of Monte Sierpe reinforces its interpretation as a critical point for gathering and organizing goods and people:

• Strategic Location: Monte Sierpe is situated at a critical crossroads. It lies near the intersection of major roads and one of the most important pre-Hispanic coast-highland trade routes.
• Chaupiyunga Context: The site is located in the chaupiyunga, a transitional ecological area where coastal, local, and highland groups commonly came together to exchange products and negotiate for access to land, water, and minerals. This location made it an ideal place for communities to deposit goods.

Hypothesized Function 1: Barter Marketplace (Late Intermediate Period)

The authors propose that Monte Sierpe originally functioned as a barter marketplace under the Chincha Kingdom during the Late Intermediate Period (AD 1000–1400).

• Chincha Economic Context: The Chincha Kingdom, a wealthy and centralized polity, had a burgeoning population, high agricultural productivity (possibly enhanced by guano fertilizer), and a variety of economic specialists, including fisherfolk, farmers, artisans, and merchants. This complexity created the necessary foundations—surplus, specialization, and density—for the emergence of marketplaces.
• Market Operation: Historical records confirm that markets (tiangues) and fairs existed frequently in the Andes for exchanging goods. Barter markets, while lacking currency, rely on units of equivalency and account.
• Role of the Holes: In this scenario, the large number of holes would have allowed for a standardized system of equivalencies typical of barter markets. Depositing goods in the holes would have made information about the quantity of available goods public and organized, helping to draw together producer-specialists, mobile traders, and administrators for periodic, ritualized exchange. The exchanges were likely limited to locally grown goods, such as maize and cotton, exchanged between neighboring communities.

Hypothesized Function 2: Accounting Device for Tribute (Late Horizon)

Following the Inca conquest (AD 1400–1532), Monte Sierpe may have been adapted to the centralized Inca economic system, functioning as an accounting device for tribute collection and redistribution.

• Inca Administrative System: The Inca imposed the mit’a labor-tax system, requiring communities (organized by decimal administration) to provide labor or its equivalent in produce. Khipus were integral to keeping records of census information, inventory, and tribute.
• Analogy to Inkawasi: The site's regular numerical patterning is comparable to grid-like arrays of squares found on the floors of sorting spaces at the Inca administrative center of Inkawasi, where khipus were also found, suggesting a similar purpose of counting and sorting different goods.
• Role of the Sections: As an Inca accounting device, each section at Monte Sierpe could have been linked to a particular social group for tax payment and the redistribution of commodities. Variations in the number of holes across sections may reflect differences in tribute levels or the number of taxpayers from specific communities, aligning with the Inca mit’a system.
• Administrative Control: This function is consistent with Monte Sierpe's location between the major Inca administrative centers of Tambo Colorado and Lima La Vieja, making it an ideal site for commodity accounting, collection, and control.

In summary, the research supports a model where Monte Sierpe evolved from a localized barter market managing surpluses under the Chincha Kingdom into a state-integrated accounting mechanism for Inca tribute, demonstrating how Indigenous communities modified the landscape to structure interaction and manage resources across changing political environments. The site itself, with its segmented and numerically patterned holes, functioned as a physical spreadsheet or calculating structure.

Monte Sierpe, or the ‘Band of Holes,’ has generated numerous hypotheses regarding its function since its documentation in 1933. However, the recent integrated analysis utilizing drone imagery and microbotanical evidence has provided detailed data that offers little support for many of the previous alternative explanations, allowing researchers to focus on the interpretation of Indigenous accounting and exchange.

The sources explicitly state that identification of numerical patterning in hole counts and microbotanical evidence of crops and wild plants in the holes provides little support for connecting Monte Sierpe with defense, water collection, fog capture, burial, or mining.

Hypotheses Lacking Archaeological Evidence

Several historical hypotheses were dismissed due to a lack of physical or contextual evidence at the site itself:

Defense

The idea that Monte Sierpe functioned for defense has been proposed. Although comparisons have been drawn to features worldwide, such as bands of shallow holes (hulbæltet) used to defend Iron Age settlements in Europe, the sources find no evidence of military activity at the Peruvian site.

• There is no evidence of related fortification at Monte Sierpe.
• There are no signs of attacks or defensive responses.
• There is a notable lack of typical Andean weapons, such as slingstones (bolas), documented at other fortified Andean sites.
• Researchers caution that drawing conclusions solely based on morphological similarities with other built features worldwide does not necessarily equate to functional equivalence.

Burial and Mining

The hypotheses that the holes served as a burial ground or mining area were also rejected based on site surveys:

• It is unlikely that Monte Sierpe was a mining area, as no evidence of copper or silver ores has been found.
• It is unlikely that the site functioned as a burial ground, as no human remains were found, aside from a few intrusive tombs at the southern end.

Storage

One hypothesis that the research specifically aimed to test was Hyslop's (1984) proposal that the site was used for storing goods. While the microbotanical evidence confirms the presence of pre-Hispanic crops like maize and Cucurbita in the holes, suggesting items were placed there, the overall structural layout (numerical patterning and segmentation) led the researchers to suggest that the primary function was accounting and exchange of these goods, rather than mere long-term storage.

Hypotheses Refuted by Environmental Context

Hypotheses relating to agricultural functions or water management were inconsistent with the environmental reality of the site’s location:

Water Collection, Fog Capture, and Gardening

The hypothesis that the holes were used for water collection, fog capture, or as a form of sunken field (like those used for grape cultivation in Lanzarote) lacks strong support.

• Rainfall is effectively non-existent at the high altitudes where Monte Sierpe is located in the Pisco Valley.
• Andean sunken fields rely on groundwater, which is not available on the hill slope where Monte Sierpe is situated.
• Although the area experiences ephemeral fog oases (lomas), the water resulting from fog capture would not have been sufficient to grow most of the identified plants in situ (on the site itself).
• Furthermore, the nearby Pisco River provides sufficient water for agriculture year-round, negating the necessity for such intensive fog capture technology for large-scale crop production.

Unconfirmed and Pseudo-Archaeological Narratives

The researchers addressed two other categories of interpretation:

Geoglyph

The study's results, while refuting many hypotheses, cannot rule out the possibility that the site functioned as a geoglyph.

Pseudo-Archaeology

The site has gained prominence among the pseudo-archaeological community as an ‘unexplained mystery,’ particularly in connection with ‘ancient astronaut’ ideology. The authors stress that it is essential to challenge such narratives with clear archaeological evidence and reasoning to ensure accurate representation of local heritage and Indigenous knowledge in public discourse. The entire research effort, by proposing a function rooted in Indigenous numeracy and economic practice, serves as a rebuttal to these unexplained mystery narratives.

The sources place Monte Sierpe's initial function within the powerful Chincha Kingdom context during the Late Intermediate Period (AD 1000–1400), arguing that the site likely originated as a barter marketplace before later being incorporated into the Inca system.

The Chincha Kingdom: A Powerful and Specialized Polity

The Chincha Kingdom was one of the most powerful polities located on the Peruvian southern coast during the Late Intermediate Period, with territory spanning both the Chincha and Pisco valleys. The characteristics of this kingdom provided the "critical foundations for the emergence of marketplaces" like the one hypothesized at Monte Sierpe.

Key aspects of the Chincha Kingdom context include:

Population and Production

• High Population Density: Colonial-era records indicate that at least 30,000 male tribute payers existed in the area, suggesting an estimated total population exceeding 100,000 people.
• Agricultural Productivity: The Chincha lands were reportedly highly productive and capable of supporting large-scale agriculture. This productivity was enhanced by the annual renewal of rich alluvium from seasonal rivers and was likely further boosted by seabird guano (excrement), an effective fertilizer exploited on nearby islands, including the Chincha Islands offshore from the Pisco and Chincha valleys.
• Settlement and Infrastructure: High population estimates are supported by the archaeological identification of dense Late Intermediate Period and Late Horizon settlement, including defensive sites, administrative complexes, cemeteries, irrigation canals, and cultivation fields across the coastal valleys. Aerial photographs from 1933 show an elaborate irrigation system in the Pisco Valley just 4km west and below Monte Sierpe.

Economic Specialization and Trade

The Chincha Kingdom was characterized by a high degree of economic specialization, which drove the need for organized exchange.

• Specialized Communities: The kingdom was reportedly composed of distinct communities of economic specialists, including 10,000 fisherfolk, 10,000 farmers, and 6,000 artisans and merchants.
• Merchants and Trade Networks: Chincha merchants were particularly valuable to the kingdom, substantially expanding interregional trade networks. These merchants engaged in both seafaring trade on balsa rafts along the coast and inland trade with highland regions using llama caravans. They acquired prestigious items such as silver, gold, and emeralds, exchanging them with lords from nearby regions, like the Ica Valley.
• Producer-Specialists: Other local and nonlocal craft specialists, such as metalworkers, carpenters, herders, potters, tailors, and miners, were integrated into this large political entity (señorío or kingdom), characterizing the economic organization of Late Intermediate Period coastal polities.

Monte Sierpe as a Chincha Barter Marketplace

The sources propose that Monte Sierpe, which dates to at least the Late Intermediate Period, served initially as a barter marketplace under Chincha control.

Rationale for a Market Function (Barter Marketplace Hypothesis):

1. Economic Criteria: The site’s hypothesized function meets the criteria for marketplace emergence: the Chincha society had agricultural surplus (possibly guano-driven), high population density, and significant economic specialization.
2. Strategic Location: Monte Sierpe is located in the chaupiyunga, a transitional ecological area between the coastal plain and highland valleys. This position was a focal point for interaction where coastal, local, and highland groups typically gathered to exchange products and negotiate access to resources like land, water, and minerals. The site is situated near the intersection of major roads and a significant pre-Hispanic coast-highland trade route, increasing the probability of locating suitable trading partners.
3. Role of the Holes in Exchange: In a barter market, where currency is absent, units of equivalency and account are necessary. The large number of segmented holes would have provided a standardized system of equivalencies. The holes likely provided an organized and public way for large numbers of people to deposit goods, giving participants information about the quantity of resources available.
4. Goods Exchanged: Microbotanical evidence confirms the presence of pre-Hispanic crops like maize and Cucurbita in the holes. At this time, exchanges may have been limited to locally grown goods, such as maize and cotton, traded through interactions among neighboring communities within Chincha and adjacent regions like Ica.
5. Social Context: Historical records confirm the existence of frequent markets (tiangues) and fairs in the Andes for exchanging goods, often involving ritualized and public behaviors structured around customarily fixed equivalences.

Transition to Inca Control

The Chincha Kingdom maintained its economic prominence until the Inca conquest in the fifteenth century. Although the Inca brought the kingdom under their rule, the Chincha leaders were given considerable latitude and autonomy. After the conquest, the Inca seized agricultural land, intensified fishing production, reorganized the populace into a decimal-based administration, and conducted censuses to levy tribute. This transition led to the second phase of Monte Sierpe's use, where it functioned as an accounting device for tribute extraction within the Inca state.

In essence, the economic success and administrative complexity of the Chincha Kingdom during the Late Intermediate Period created the environmental and social context necessary for Monte Sierpe to emerge as a central node for organized, local barter and resource management. The site served as a physical apparatus for managing the flow of goods produced by the specialized Chincha economy.