-->PONE-D-26-03379-->-->Formative-period geoglyphs in the middle Chillón Valley, Peru: survey documentation, ceramic association, and null-model tests of route proximity-->-->PLOS One

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Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. -->

Reviewer #1: Partly

Reviewer #2: Yes

Reviewer #3: Partly

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-->2. Has the statistical analysis been performed appropriately and rigorously? -->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: No

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Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

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-->5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: Overall, there are some very interesting questions that can be considered by placing these geoglyphs into a landscape and cultural context. The analysis here is transparent in its methods and expectations, which is a positive thing, but it feels like the small dataset could be stronger if it were integrated into a broader archaeological context, rather than abstracted through a simulation that feels like it lacks some key information.

Lines 184-185: Given the number of geoglyphs encountered in the project, it would be helpful to know how the two quebradas discussed here were selected for analysis.

Line 196ff.: Were the six Formative sherds the only surface finds recorded by the field research, or just the earliest pottery? If there were other artifacts (later ceramic phases, preceramic lithics), it would be good to tabulate those and to discuss the interpretation of those collections. If these were the only artifacts encountered, then it would be good to state that clearly.

Lines 218-226: Given that no Formative pottery was reported for Pichausa, it would be helpful to know how the geoglyphs in that quebrada were identified as Formative.

Lines 230ff.: How is the chronology of roads/routes determined? If these are not validated as contemporaneous with the construction of the geoglyphs, what interpretive value do they have in the modeling exercise? Since these are not all of the existing routes, how were these selected?

Line 441ff.: It would be helpful to have a broader context for the settlement history of this part of the valley, either through research by the authors and/or through reference to Silva’s regional survey. If there are Formative settlements nearby, that might complicate arguments that the 6 sherds encountered are associated with the earliest construction of the geoglyphs.

Lines 446-448: If one of the two study areas is chronologically inconclusive, then the interpretive power of the analysis seems restricted to general inferences about the extent to which geoglyph construction was done in proximity to low-cost routes. I worry about the potential for circularity here, since the study does not incorporate all known or possible routes in the area. It would be interesting to consider some alternatives to the siting of geoglyphs, such as overall visibility or location along routes between known Formative sites.

Lines 476ff.: The point about Huarabi’s distinctive association with Formative pottery seems like it could be used productively to consider the Formative “sphere of activity” referenced here, which would probably require multiscalar discussion of settlement patterns, landscapes of movement, and activity patterns that could be related to the geoglyphs there. The cultural question seems more compelling than the comparison of the two quebradas, given the limited inferences that can be made with the other geoglyphs.

Lines 482ff.: If movement is relatively channeled through these quebradas, what purpose do the geoglyphs play? On the map it looks like the quebradas might be a shortcut to avoid a meandering curve in the main valley, presumably used by people moving between regions.

It might be worthwhile to mention some of the geoglyph work farther south in Peru in the introduction, and there is a new article by Stanish et al. that might help to articulate a stronger cultural argument:

Stanish, Charles, Henry Tantaleán, Carito Tavera, Jacob Bongers, and Karen Wise. "A Theory of Andean Geoglyphs." Journal of Anthropological Research 82, no. 1 (2026): 000-000.

NB: My analytical expertise does not extend to the kind of simulation modeling presented here, and the journal is encouraged to consult a reviewer who can address the design and execution of that part of the study.

Reviewer #2: This is a good paper and interesting contribution to the literature on geoglyphs. I suggest publication with some modifications at the discretion of the authors and editor.

First the authors must add an explicit statement in the beginning noting tht the Antiquity piece previously published by the authors describes the broader survey project. It is the overview publication. Then note that this manuscript analyzes a specific set of data from this larger project. This manuscript adds a new analysis which is a Monte Carlo null-model inference and sensitivity analysis.

The paper has an overabundance of jargon. A native English-speaking editor should clean this up.

The statistical analysis seems to be sound and appropriate. I see no serious issues but a statistician should be consulted.

Line 106. “The Nasca-Palpa corpus dominates the international literature”. This is true but there are other published works on geoglyphs in Arequipa, Casma, Chincha and northern Chile. These should be briefly noted to provide a fuller research context. This paper in particular seems very relevant to this manuscript: Bikoulis, P., Gonzalez-Macqueen, F., Spence-Morrow, G., Bautista, S., Alvarez, W.Y. and Jennings, J., 2018. Ancient pathways and geoglyphs in the Sihuas Valley of southern Peru. Antiquity, 92(365), pp.1377-1391

It is very important that the authors expand on the survey methodology. If this was a full regional coverage methodology that included modern and presumed earlier routes as welll as areas away from these routes, the interpretation is strongly supported. However, if the pedestrian survey overly weighted these routes, then this could inflate apparent route proximity. Figure 2 seems to suggest that the survey was focused on pathways since they tend to follow gullies. These pathways should be included in the map. This is an issue that has to be addressed. Did the drone survey look for geoglyphs outside of the pathways? Clearly, if there was no systematic survey away from the routes then the interpretation is weakened because the methodology insures that only geoglyphs near the roads were studied. On the other hand, if the Monge Carlo null model took that into consideration, the authors need to be forcefully explain this.

The sample of formative pottery to date the geoglyphs is extremely low. One should recall that some of the earliest work on the Nazca geoglyphs claim that they were LIP in date based upon diagnostic pottery found on the surface on or near the geoglyphs. Subsequent work indicated that this was not the case. It's very difficult to date geoglyphs, I understand this and the discussion in lines 476 – 481 should be highlighted. In that regard, the authors need to demonstrate some geographical linkage to Formative sites, even if these are far away but on the travel routes documented for the geoglyphs. In this regard, lines 160 -167 in the manuscript should explicitly tie the geoglyphs to the U shaped buildings in the valley. Furthermore, if there are other sites from different time periods in the valley then these should be mentioned.

Reviewer #3: This manuscript presents previously unpublished geoglyph contexts from two quebradas of the middle Chillón Valley and applies explicit counterfactual (Monte Carlo) spatial models to evaluate their relationship to mapped circulation features. The analytical framework is methodologically sound and, in principle, well suited to evaluating hypotheses about non-random spatial relationships between geoglyphs and circulation features. The authors are also commendably cautious in distinguishing statistical deviation from cultural interpretation.

That said, several substantial issues must be addressed before the manuscript can be considered suitable for publication in PLOS ONE. These issues concern the inferential scope of the analysis, the adequacy of the spatial data and landscape modeling, chronological interpretation, and compliance with research ethics and permitting requirements.

1. Inferential scope, sample size, and statistical interpretation

Despite careful caveating, the Discussion and Conclusions still over-interpret results derived from an extremely small empirical sample. The Formative dataset comprises only four geoglyph units (two per quebrada), supplemented in Huarabí by six surface ceramic findspots. Under these conditions, Monte Carlo p-values (e.g., p = 0.026 under corridor-restricted availability) cannot be treated as substantive evidence for “structured” placement. At most, the results demonstrate a discrepancy between observed and simulated distance distributions under a single, highly specific operationalization of availability and route proxies. The non-monotonic behavior observed in the buffer sweep—including sign reversals in Δmedian—clearly indicates that inference is highly sensitive to how feasible placement space is defined. This instability substantially weakens any behavioral interpretation. The manuscript should therefore be reframed more explicitly as exploratory and methodological, with emphasis placed on effect sizes, sensitivity diagnostics, and model dependence rather than on thresholded statistical significance.

2. Absence of terrain-based feasibility modeling (critical limitation)

Most critically, the analysis operates without a bare-earth Digital Terrain Model (DTM) and without any explicit modeling of landscape feasibility. The study relies on UAV-derived surface models and planimetric representations of geoglyphs and routes, but does not incorporate slope, exposure, microrelief, substrate stability, or geomorphic suitability into either the null models or the definition of feasible placement space. This omission is not a minor technical detail. Geoglyphs cannot be constructed everywhere in a quebrada landscape, and feasible placement space is inherently heterogeneous. Treating all locations within the surveyed polygon (or its buffered expansions) as equally available risks overestimates spatial freedom and fundamentally mis-specifies the counterfactual model against which observed patterns are evaluated. The sensitivity analyses using progressively expanded availability windows demonstrate that inference is highly dependent on how placement space is defined. While the authors correctly describe this as scale dependence, the deeper issue is that window-based buffering is a geometric proxy for feasibility rather than a substantive model of it. Without terrain-based constraints, deviations observed under broader windows may reflect null-model inflation rather than meaningful behavioral structure.

3. Spatial accuracy and data resolution

Interpretation is further limited by the absence of explicit accuracy metrics for the UAV-derived spatial data. No information is provided on ground sampling distance (GSD), georeferencing error (e.g., RMSE), or the use, number, and quality of ground control points. Given that reported effect sizes and median distance differences often operate at the scale of tens of meters, positional uncertainty may be comparable in magnitude to the observed effects. These uncertainties should be quantified or, at least, explicitly bounded.

4. Conceptual separation of movement constraints and route association

The Discussion occasionally conflates two analytically distinct phenomena:

(a) general movement constraints imposed by quebrada topography, and

(b) hypothesized association between geoglyph placement and specific circulation routes.

The former does not, by itself, support the latter. Without explicit modeling of feasibility (e.g., slope, substrate, visibility) independent of mapped routes, proximity to routes may simply reflect geomorphological channeling and survey process rather than intentional placement relative to circulation corridors.

5. Chronology and ceramic associations

The treatment of Formative ceramics in Huarabí is appropriately cautious in places but still leans too far toward cultural placement. Given the small number of surface finds, their utilitarian character, and the absence of stratigraphic association with geoglyph construction, these materials should be framed strictly as evidence for Formative-period activity in the vicinity, not as support for geoglyph dating. Statements suggesting that Huarabí provides a “strong basis” for situating geoglyphs within a Formative sphere should be softened accordingly.

6. Fieldwork authorization and research ethics (major omission)

The manuscript states that a “systematic pedestrian survey” was conducted in 2021–2022, but it does not provide formal information regarding authorization by the Ministry of Culture of the Republic of Peru. In Peru, all archaeological fieldwork—including survey—must be conducted under a formally approved archaeological project supported by:

• a current Resolution (Resolución Directoral) issued by the Dirección de Calificación de Intervenciones Arqueológicas of the Ministry of Culture, and

• active COARPE registration, including valid annual habilitación for the project director.

At present, the manuscript includes only acknowledgements, without providing permit numbers, issuing authority, or confirmation of COARPE status. This is a serious omission. For ethical compliance and transparency, the authors must explicitly state the permit number(s), issuing body, and year(s) of validity, or otherwise clarify the legal framework under which the fieldwork was conducted. Without this information, the manuscript does not meet basic standards of research ethics and legal compliance.

7. Recommendations

I recommend major revision, conditional on the following:

• reframing the analytical claims as explicitly exploratory and model-conditional;

• removing or further softening language that implies patterned or intentional route-related placement;

• explicitly acknowledging the absence of terrain-based feasibility modeling and its implications for inference;

• clarifying the limits of chronological interpretation based on surface ceramics; and

• providing full and explicit documentation of Peruvian archaeological permits and authorizations.

Addressing these points would substantially strengthen the manuscript’s methodological integrity and ensure compliance with both scientific and ethical standards.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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-->PONE-D-26-03379R1-->-->Geoglyphs and Formative-period activity in the middle Chillón Valley, Peru: ceramic association and null-model tests of route proximity-->-->PLOS One

Dear Dr. Mesia-Montenegro,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.-->-->

Please submit your revised manuscript by Jun 22 2026 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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We look forward to receiving your revised manuscript.

Kind regards,

Christian Reepmeyer, PhD

Academic Editor

PLOS One

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Additional Editor Comments:

Please review the comments closely, particularly of Reviewer 2 in reference to the tentative nature of the results and the relative small size of the sample dataset.

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Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.-->

Reviewer #1: All comments have been addressed

Reviewer #3: (No Response)

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-->2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. -->

Reviewer #1: Yes

Reviewer #3: Partly

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-->3. Has the statistical analysis been performed appropriately and rigorously? -->

Reviewer #1: I Don't Know

Reviewer #3: Yes

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-->4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: Yes

Reviewer #3: Yes

**********

-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

Reviewer #3: No

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-->6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: The revised manuscript is much improved, and the authors clearly review their responses to reviewer comments in the cover letter. The overall purpose of the article is clearer, and it now does a nice job of balancing between very careful fine-grained empirical analysis and a broader cultural context that is very cautious about inferences being made, and thoughtful about prospective future directions for the work. There are some minor edits that need to be made with the text (accenting, bolded text where it should not be, etc.), but I think this paper should be accepted for publication.

Reviewer #3: The revised manuscript significantly enhances transparency, interpretive caution, and adherence to ethical standards. The authors have thoughtfully addressed the previous review and have commendably reframed their claims to be model-conditional and exploratory instead of deterministic. However, some key methodological issues, especially in terrain-based feasibility modeling, remain unresolved, limiting the interpretive value of the analysis. Although the manuscript has improved significantly, it still needs specific clarifications and a softer presentation of its conclusions before publication.

The revision significantly enhances the manuscript by clarifying that the analysis is exploratory, model-dependent, and affected by how availability is defined. The authors now avoid interpreting Monte Carlo p-values as direct indicators of intentional or culturally meaningful route placement, instead focusing more on effect sizes, sensitivity analyses, and the variability of results across different windows. This correction is both welcome and important. The limited empirical sample is now more openly acknowledged, and the discussion no longer portrays the results as covering the entire valley or being behaviorally deterministic. However, some language still implies a stronger notion of “structured placement" than the data can support, especially considering the dataset includes only four geoglyph units and six ceramic findspots. The new framing is largely acceptable, but the manuscript could benefit from further subtle adjustments: the results should be uniformly described as deviations from specific tested null models rather than as proof of broader spatial structuring in archaeology. Some phrases continue to suggest a greater degree of spatial organization than the data justifies.

The revision also improves transparency by explicitly acknowledging the lack of terrain-based feasibility modeling, including a bare-earth DTM, slope, substrate, and geomorphic suitability. Adding geomorphic screening and emphasizing that buffer-based availability windows are only geometric proxies for feasible placement areas are valuable clarifications. These updates enhance the methodology's transparency and better align the interpretation with the data's actual limitations. However, the main issue persists: feasibility is still not directly modeled, and the null model assumes spatial availability that may not reflect true construction constraints in quebrada landscapes. Consequently, observed deviations might partly result from misspecification of the counterfactual rather than genuine spatial patterns. Although this limitation is now acknowledged, it would be clearer to explicitly state that the absence of terrain-based feasibility modeling fundamentally restricts the interpretive scope of the analysis and confines the results to exploratory, model-dependent insights.

Regarding spatial accuracy and data resolution, the revision effectively addresses the initial concerns by clearly acknowledging the lack of formal spatial-accuracy metadata, such as ground sampling distance (GSD), georeferencing error, and ground-control-point statistics. The authors smartly reframe their analysis as being conducted at a broad spatial scale and avoid making claims that rely on high positional accuracy. This clarification enhances the credibility of the spatial analysis and ensures the interpretation matches the data's actual resolution. However, the issue remains a limitation, especially since some reported effect sizes occur at relatively short distances where positional uncertainty could be significant. While the manuscript now treats this as a constraint rather than an oversight, it would be improved by explicitly stating that spatial uncertainty might be comparable to some observed differences, emphasizing the exploratory and non-deterministic nature of the findings.

The revision significantly improves the distinction between movement constraints and route association. The authors now clearly differentiate the general movement limitations caused by quebrada topography from the hypothesis of intentional geoglyph placement related to specific circulation routes. This distinction is consistently explained throughout the revised Discussion and is supported by explicit statements noting that proximity to mapped routes alone does not imply intentional association. Clarifying that geomorphological constraints and cultural patterns are analytically distinct enhances the interpretive framework and minimizes the risk of circular reasoning. However, while the conceptual separation is well established, the analysis still lacks independent terrain-based modeling, preventing a clear disentangling of geomorphology's role from potential cultural siting preferences. Thus, the revision addresses the conceptual issue, but empirically separating these factors remains a task for future research.

Regarding chronology and ceramic associations, the revision significantly enhances how the available evidence is addressed by adopting a cautious and appropriately limited interpretive approach. The authors now clearly state that Formative ceramics from Huarabí indicate nearby activity rather than directly dating geoglyph construction. They also openly acknowledge the small sample size, surface context, and potential post-depositional mobility of the artifacts. The difference between Huarabí and Pichausa is now more transparently explained, with Pichausa described as chronologically unresolved rather than implicitly attributed. These corrections are important and necessary. However, some phrasing still suggests that Huarabí provides a "stronger” basis for cultural attribution, which may overstate what limited, ambiguous evidence can support. Overall, the revision could be improved by refining the language to emphasize that ceramics are only useful as contextual indicators of local activity, not as definitive markers of chronological or cultural placement.

Regarding fieldwork authorization and research ethics, the revised manuscript fully addresses this concern. It ensures the manuscript complies with Peru's archaeological research standards and enhances its transparency and credibility. Including this information was necessary and is presented clearly and professionally.

Regarding the conceptual contribution and interpretive framing, the revision marks a notable improvement in caution, transparency, and alignment between data and claims. The manuscript now regularly emphasizes that its findings are model-dependent and stops short of claiming definitive evidence of culturally meaningful spatial patterns. The shift to highlight exploratory analysis, conditional inference, and the constraints of data quality and sample size is fitting and bolsters the overall argument. Additionally, the discussion becomes more constructive by placing the geoglyphs within a wider landscape context, including movement, encounter, and possible ritual activities, rather than concentrating solely on route proximity. Nevertheless, the interpretive contribution remains somewhat limited, mainly because empirical constraints (such as small sample size, weak chronological control, and lack of terrain-based feasibility modeling) limit the strength of cultural inferences. Although these limitations are now acknowledged, framing the main contribution more explicitly as methodological and exploratory, rather than as offering a substantive cultural explanation, would enhance the manuscript.

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Reviewer #1: No

Reviewer #3: No

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Geoglyphs and Formative-period activity in the middle Chillón Valley, Peru: ceramic association and null-model tests of route proximity

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