{"id":"43bc295e-376c-434e-ad94-2084284b4af4","arxiv_id":"2607.14201","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"The orientations of 324 Amazonian rectangular geoglyphs are non-random and cluster near the solar arc, indicating intentional solar alignment.","lead":"The paper measures the orientations of 324 rectangular Amazonian earthworks (geoglyphs) from satellite images and finds that their directions are non-random, peaking near the summer-solstice sunrise and due east. If correct, it is the first quantitative evidence that the builders aligned these likely ceremonial structures with the annual solar cycle.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Untested road/topography alignment could explain orientation peaks; solar claim requires a control test.","rationale":"The non-randomness of orientations is plausible and the global p-value is impressive, but the paper's central claim is the solar interpretation. The most direct alternative is that earthwork orientations are determined by the road network that connects them, or by local terrain. This alternative is mentioned but never evaluated: the author even cites descriptions of the roads but does not measure their orientations. Since the measured azimuth is defined as the side closer to east, a road approaching from the southeast at 115° would make the earthwork's east-closer side also 115°, trivially producing a 'summer solstice' peak. The same mechanism could create the 68° peak. A simple measurement of road orientations would settle the issue. Additionally, the statistical reporting contains an obvious inconsistency (p≈0.5 called 'borderline'), which raises doubts about the computed significances; the reader's conditional verdict is therefore appropriate. The proposed test is concrete, uses the same dataset, and would distinguish a practical cause from an astronomical one. Since the reader already identified this missing control, my read does not change the verdict.","tokens_in":5555,"tokens_out":7036,"duration_ms":64036,"concrete_test":"From the same Google Earth Pro imagery, measure the azimuth of the straight 'road' segment approaching each of the 324 earthworks (and, for isolated structures, the azimuth of the nearest drainage/contour line). Apply the same 'side closer to east' folding rule to these control azimuths. Then: (1) compute the circular-circular correlation between earthwork azimuths and road azimuths; (2) rerun the peak analysis on earthworks without any visible road, or using the road azimuth as a covariate. If the earthwork azimuths are strongly correlated with road azimuths (|r| > 0.5) and the 68°/115° peaks disappear in the no-road subset, the solar interpretation is not supported. If no such correlation exists, the solar claim is strengthened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that the orientation peaks at 68°, 89.5°, and 115° reflect deliberate solar alignments hinges on excluding non-astronomical causes. The paper explicitly acknowledges 'this design may be due to practical reasons' (Section 3) but never probes them. The double-bank straight 'roads' connecting many earthworks—highlighted in the Introduction and cited from Saunaluoma et al. 2018 and Kalliola et al. 2024/2026—are not measured. If the east-closer side of each rectangle is systematically aligned with the approaching road (which may itself follow ridges or drainage), the same peaks would appear without solar intent. The only null hypothesis tested is uniform azimuths; no comparison is made with road orientations or local terrain. Furthermore, the 'borderline evidence (p ≈ 0.5)' claimed for the 89.5° peak is internally inconsistent—p=0.5 is not borderline but non-significant—suggesting that the peak-significance statistics may be misreported and undermining the reported p-values for the other peaks.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents a remote-sensing study of the orientation of 324 square/rectangular Amazonian earthworks (geoglyphs) in Acre, Brazil, using Google Earth Pro. The author defines the azimuth of each structure as the side closest to due east and reports a strongly non-uniform distribution (global p=1.5e-15), with peaks at approximately 68°, 89.5°, and 115°. The 115° peak is identified as the summer-solstice sunrise, the 89.5° peak as a cardinal (east) orientation, and the 68° peak as an early-dry-season/agricultural marker. The author argues that these results indicate deliberate solar/cardinal orientation and a ceremonial, rather than practical, function for the structures.","tokens_in":5795,"tokens_out":6202,"duration_ms":60416,"significance":"If the central claim is established, this would be the first archaeoastronomical study of the Acre geoglyphs and a valuable contribution to the debate on their function. The work makes creative use of Google Earth Pro, provides openly available data (supplementary material and kmz file), and applies explicit azimuth definitions. However, the significance of the paper is currently limited by incomplete statistical reporting, an internally inconsistent peak-significance statement, and the absence of any test of non-astronomical explanations. The conclusion that the non-random orientation reflects solar intent is plausible but not yet demonstrated.","major_comments":[{"comment":"The statistical methodology is not fully specified. The global p-value of 1.5×10⁻¹⁵ is reported without naming the test statistic, the null model, or the binning procedure. Peak significance values are internally inconsistent: the text first claims 'three statistically significant peaks' and then reports 'borderline evidence (p≈0.5)' for the central 89.5° peak. A p-value of 0.5 is not borderline; it indicates no evidence. This is load-bearing because the identification of three solar/cardinal peaks is the paper's principal result. Provide a precise description of the significance test (including null distribution, peak detection, and multiple-testing correction) and report p-values consistently. If the central peak is not significant, exclude it from the definitive results or explicitly downgrade it to a hypothesis.","section":"§2–3"},{"comment":"The paper does not test non-astronomical explanations for the non-uniform azimuth distribution. The author acknowledges (Section 3) that 'this design may be due to practical reasons,' but the only null hypothesis tested is uniformity. The Introduction emphasizes the network of double-bank straight roads connecting earthworks, but the orientations of these roads are never measured. If the rectangular structures are systematically aligned with approaching roads that follow ridges or drainage, the same azimuth peaks could emerge without solar intent. The author should measure road orientations and/or compare the earthwork azimuth distribution with a control sample (e.g., local terrain aspect, modern field boundaries) or with a null model that incorporates such alignments. Without this, the inference from non-uniformity to deliberate solar alignment is not warranted.","section":"§3–4"},{"comment":"The interpretation of the 68° peak as an early-dry-season/agricultural marker relies on modern climatic and agricultural data (rainfall in Rio Bravo, current double-cropping of corn) without evidence that these conditions existed in the pre-Columbian period. The text itself says 'at least today,' making this a post hoc historical analogy. The peak is only ~2° from the winter-solstice sunrise azimuth, and the two calendar dates (end of May / mid-July) are not independently supported by any archaeological trace. Frame this as a hypothesis rather than a result, and test it against alternative explanations (e.g., horizon-height variations at the sites, or a solstitial interpretation). This is load-bearing for the claim of agricultural interest in the Sun.","section":"§4"},{"comment":"The selection criteria for including parallelograms with internal angles deviating no more than 2° from 90°, and the 'average' used for slightly bended parallelograms, are arbitrary and untested. Since these criteria define the sample, the paper should show that the reported peaks are robust to the tolerance threshold and to the averaging procedure. A different threshold could alter the sample and the resulting azimuth distribution, affecting the central claim of non-random orientation and peak positions.","section":"§2"}],"minor_comments":[{"comment":"The phrase 'without doubts' overstates certainty for a study that the author later calls 'preliminary' (Section 1). Soften the abstract to match the cautious language in the body.","section":"Abstract"},{"comment":"Typo: 'tecuques' should be 'techniques.' Also, 'Arce' appears in Section 4; should be 'Acre.'","section":"§2"},{"comment":"The estimated uncertainty of ±1° in azimuth is plausible but not justified by any inter-operator test. A short reproducibility check or reference to prior work would strengthen this.","section":"§2"},{"comment":"The histogram (Fig. 2) and curvigram (Fig. 3) would benefit from error bars or confidence bands, especially given the small counts in some bins.","section":"§3"},{"comment":"The use of a 3-Gaussian mixture is stated, but the number of components is a free parameter. Show sensitivity to the number of components, not only to the kernel type (Epanechnikov).","section":"§3"},{"comment":"Reference typo: 'Shahn 2012' should be 'Schaan 2012.' Also check the citation 'Kalliola, et al. 2024,2026' for consistency with the reference list.","section":"§1"},{"comment":"The suggestion that rhomboidal structures are ceremonial because no practical purpose is apparent is an argument from ignorance. Present this as a tentative observation, not as supporting evidence for the main conclusion.","section":"§4"}],"recommendation":"major_revision","confidential_remarks":"The paper addresses a timely and interesting topic, and the public release of the dataset is commendable. However, the statistical reporting and the lack of control for non-astronomical alignments are substantial issues that should be addressed before publication. The abstract and conclusion currently overstate the strength of the evidence, and the author should be encouraged to reframe the solar/agricultural interpretation as a hypothesis pending further testing."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The thing to know: this is the first orientation study of Acre geoglyphs, and the basic empirical result—324 measured rectangular earthworks with a strongly non-uniform azimuth distribution (global p around 1e-15)—is worth taking seriously. The non-randomness is not the issue. The issue is whether the specific peaks at 68°, 89.5°, and 115° are deliberate solar alignments or an artifact of something like road orientation, terrain, or post-hoc selection.\n\nWhat the paper does well: the dataset itself is a new contribution. Using Google Earth to measure 324 structures and folding them to the side closer to east is a sensible, standard archaeoastronomical procedure. The quick decay of the distribution outside the solar arc (66°–114°) is visually striking and does suggest the builders cared about the sun's annual range. The author also acknowledges that the design could have practical reasons and lists real limitations up front, which is honest.\n\nSoft spots, in order of softness. First, the statistics are under-specified. The global p-value is reported as 1.5e-15, but the test is never named. The peak significances are reported as p≈5e-10 and p≈0.5 for the 89.5° peak, which is then called \"borderline.\" That is a mischaracterization—p=0.5 is non-significance, not borderline. If the central peak is not significant, the cardinal-orientation claim has to rest on the rhombus anecdote, which is a handful of examples. Second, the load-bearing confound is untested: the paper mentions the double-bank straight roads connecting earthworks but never measures their orientations. If those roads follow ridges or drainage, and the rectangles align to the roads, the same azimuth peaks could appear without any astronomical intent. The author says \"this design may be due to practical reasons\" but never probes that. Third, the 68° peak is interpreted post hoc as the end-of-May dry-season marker, with modern rainfall and corn harvest data. That is plausible, but it is not a prediction; it is an explanation after seeing the peak. Fourth, the abstract says 326 earthworks while the methods say 324; small but sloppy.\n\nWhat is not a problem: the self-citation of Magli (2008, 2025) for methodological precedent. That is standard and does not burden the central claim. The solar arc and solstice azimuths are independent quantities, not fitted parameters.\n\nWho this is for: archaeoastronomers and Amazonian archaeologists. The empirical distribution is a useful addition to the geoglyph literature, and the paper deserves a serious referee precisely because it opens a new dataset. But the solar interpretation should be presented as a hypothesis, not a conclusion, until a control against road/terrain orientations is done and the statistics are fully specified. I would send it to peer review, but with the requirement that the author releases the data and the exact test procedures, and addresses the road confound directly.\n\nRecommendation: engage—but treat the astronomical claim as provisional.","headline":"First orientation dataset of 300+ Amazonian geoglyphs shows a strong non-random signal, but the solar interpretation is under-supported and needs controls.","tokens_in":6217,"tokens_out":2084,"would_cite":false,"duration_ms":23571,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The paper claims that the rectangular earthworks of Acre were deliberately oriented to the Sun's annual cycle, with orientation clusters at 68°, 89.5°, and 115°.","keywords":["Amazonian earthworks","geoglyphs","Acre, Brazil","archaeoastronomy","solar orientation","satellite remote sensing","cardinal directions","ceremonial structures"],"falsifier":"Measure the azimuths of a control set of streams, field boundaries, and roads in the same Acre landscapes; if non-earthwork features cluster at 68°, 89.5°, and 115° as well, the solar interpretation collapses. A second check: lidar under intact forest—if hidden rectangular earthworks have uniformly distributed orientations, the visible sample is a preservation artifact rather than evidence of design.","tokens_in":5418,"feed_emoji":"🌞","tokens_out":5675,"duration_ms":54408,"temperature":0.7,"pith_summary":"This paper tries to establish that the rectangular Amazonian earthworks of Acre, Brazil, were deliberately oriented according to the Sun's annual cycle, not aligned at random. Using satellite images of 326 square and rectangular structures, the author finds three clusters of orientation: around 68°, 89.5°, and 115°. He interprets 115° as the southern-hemisphere summer-solstice sunrise, 68° as the end-of-May and mid-July Sun that announces the dry season and the second corn harvest, and 89.5° as cardinal east. The author argues this pattern supports a ceremonial, seasonal-calendar function for the structures and offers a way into the builders' worldview given the lack of written records. He explicitly leaves open that the design could stem from practical reasons.","feed_headline":"Amazonian earthworks show deliberate solar alignments","feed_subtitle":"Orientation clusters at 68°, 89.5°, and 115° point to dry-season, cardinal, and solstice sunrises.","key_machinery":"The method defines the 'azimuth' of each earthwork as the bearing, between its two adjacent sides, that lies closer to due east, so the data occupy the 45°–135° range and can be compared with the solar rising arc (66°–114° at this latitude). Gaussian-kernel density estimation locates peaks in the 326 measured azimuths, and p-value tests measure how unlikely the clustering is under a uniform null. The solar arc and the cardinal direction are the interpretive yardsticks that turn raw bearings into claims about intentionality.","core_discovery":"The paper's central claim is that the orientation of the Acre earthworks is non-random and solar. The azimuth distribution of 326 square and rectangular structures shows three clusters at roughly 68°, 89.5°, and 115°; the outer two have strong statistical support and fall inside the solar rising arc, corresponding to dates with agricultural and solstitial significance, while the central cluster indicates a cardinal (due-east) preference. On this basis the paper concludes that at least the regularly shaped geoglyphs were probably ceremonial structures built by a culture that followed the annual cycle of the Sun.","pith_inferences":["Editorial inference: The decisive control would be to compare the same azimuths with terrain slope, drainage direction, and the orientation of the connecting roads; the solar explanation would be weakened if non-earthwork features share the same peaks.","Editorial inference: The 68° cluster may encode a hydrological calendar—the onset of the dry season and river recession—rather than purely solar observation; the paper's own rainfall data point in this direction.","Editorial inference: If lidar surveys reveal earthworks under surviving forest with uniformly distributed orientations, the visible sample could be biased; a uniform hidden sample would undercut the claim of deliberate solar design."],"forward_implications":["If the alignments are real, the regular rectangular geoglyphs become among the earliest documented solar-calendrical monuments in Amazonia, predating European contact.","The pattern shifts interpretation away from defensive enclosures and toward ceremonial or seasonal gathering places, consistent with the absence of burials and defensive finds inside the structures.","The 68° peak indicates an interest not just in solstices but in specific calendrical dates tied to the dry-season onset and the second corn harvest, implying an agricultural calendar.","The cardinal peak at 89.5° suggests a symbolic quadripartition of space, a trait shared with many ancient societies.","Satellite-image orientation analysis can provide a first-pass cultural hypothesis for earthworks where excavation is not yet possible."],"fun_headline_variants":["Amazonian geoglyphs align with solar cycle","Geoglyph orientations hint at sun ceremonies","Non-random solar alignments in Amazonian earthworks","Sunrise alignments tie geoglyphs to sun's path","Amazonian earthworks show solar intentionality"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The load-bearing premise is that the observed clustering of orientations reflects deliberate solar alignment rather than a practical or environmental constraint; the paper tests only whether the distribution is uniform, not terrain slope, drainage, or road layout, and the author acknowledges the design may be due to practical reasons.","fun_headline_variants_meta":{"raw":{"variants":["Amazonian geoglyphs align with solar cycle","Geoglyph orientations hint at sun ceremonies","Non-random solar alignments in Amazonian earthworks","Sunrise alignments tie geoglyphs to sun's path","Amazonian earthworks show solar intentionality"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001993,"raw_usage":{"total_tokens":7570,"prompt_tokens":655,"completion_tokens":6915,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":399,"completion_tokens_details":{"reasoning_tokens":6842}},"tokens_in":399,"tokens_out":6915,"duration_ms":44190,"temperature":1.0,"reasoning_tokens":6842,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-02T02:54:04.896170+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the azimuths of a control set of streams, field boundaries, and roads in the same Acre landscapes; if non-earthwork features cluster at 68°, 89.5°, and 115° as well, the solar interpretation collapses. A second check: lidar under intact forest—if hidden rectangular earthworks have uniformly distributed orientations, the visible sample is a preservation artifact rather than evidence of design.","supporting_citations":[],"review_version":1}