Critical Analysis of Fish Bone Data from Anakena Cove, Rapa Nui
Examining Claims of Subsistence Change Through Taphonomic and Methodological Lenses
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June 2, 2025
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1 Introduction
The narrative of progressive faunal resource depletion has dominated archaeological interpretations of Rapa Nui’s environmental transformation. Diamond (2005), Martinsson-Wallin and Crockford (2002), and Steadman et al. (1994) constructed a picture of ecological collapse based primarily on faunal assemblages from Anakena. According to these accounts, the archaeological record indicates a progression from an abundant seabird and offshore marine resource base to an impoverished subsistence base dependent on chickens and rats. This interpretation requires critical examination.
This analysis examines fish bone data from early deposits at Anakena Cove (A.D. 800-1000) to evaluate claims of temporal shifts in fishing practices. The central question is whether the data support interpretations of resource depletion or whether alternative explanations better account for observed patterns.
2 Data and Methods
2.1 Data Source
Analysis is based on Tables 7 and 8 from Martinsson-Wallin and Crockford (2002), representing fish remains from the early component at Anakena Cove, Trench C. The assemblage dates to approximately A.D. 800-1000.
Table 1: Fish bone data from early Anakena deposits
Fish taxa were classified by habitat preference (offshore/pelagic, inshore/reef, coastal, variable) based on species ecology. Minimum Number of Individuals (MNI) served as the primary quantification method. Analysis focused on:
Table 2: Basic sample statistics for early Anakena fish remains
Metric
Value
Total Specimens (NSP)
215
Identified Specimens
56
Identification Rate
26%
Total MNI
28
The assemblage exhibits a low identification rate (26%), with only 28 individuals identified from 215 specimens. This immediately raises concerns about sample representativeness.
3.2 Taxonomic Composition
Show code
# Aggregate by familyfamily_summary <- early_fish %>%group_by(family, habitat) %>%summarise(total_mni =sum(mni), .groups ='drop') %>%arrange(desc(total_mni))# Create family composition plotp_taxonomic <-ggplot(family_summary %>%filter(total_mni >0), aes(x =reorder(family, total_mni), y = total_mni, fill = habitat)) +geom_bar(stat ="identity") +coord_flip() +scale_fill_manual(values =c("Offshore"="#2166ac", "Inshore"="#d6604d", "Coastal"="#f4a582","Variable"="#92c5de","Unknown"="#bababa")) +labs(x =NULL, y ="Minimum Number of Individuals (MNI)",fill ="Habitat Type") +theme(legend.position ="bottom",panel.grid.major.y =element_blank())# Save the plotsave_plot(p_taxonomic, "fig1_taxonomic_composition", width =8, height =6)# Display the plotp_taxonomic
Figure 1: Fish family representation in early deposits showing MNI by family and habitat association
Carangidae (jacks) dominate the assemblage with 7 MNI, followed by Labridae (wrasses) with 4 MNI. Most families are represented by only 1-3 individuals, limiting ecological interpretation.
3.3 Habitat Representation
Show code
# Aggregate by habitat zonehabitat_summary <- early_fish %>%filter(mni >0) %>%group_by(habitat) %>%summarise(total_mni =sum(mni), .groups ='drop') %>%mutate(percentage =round((total_mni /sum(total_mni)) *100, 1))# Reclassify for clearer analysishabitat_grouped <- habitat_summary %>%mutate(habitat_group =case_when( habitat =="Offshore"~"Offshore/Pelagic", habitat =="Inshore"~"Inshore/Reef", habitat %in%c("Coastal", "Variable") ~"Variable/Coastal",TRUE~"Unknown" )) %>%group_by(habitat_group) %>%summarise(mni =sum(total_mni), percentage =sum(percentage), .groups ='drop')# Create two panel figurep1 <-ggplot(habitat_grouped, aes(x = habitat_group, y = mni)) +geom_bar(stat ="identity", fill =c("#2166ac", "#d6604d", "#bababa", "#92c5de")) +geom_text(aes(label = mni), vjust =-0.5, size =4) +labs(y ="MNI", x =NULL,title ="A. Habitat distribution") +ylim(0, max(habitat_grouped$mni) *1.15) +theme(axis.text.x =element_text(angle =45, hjust =1))p2 <-ggplot(habitat_grouped, aes(x ="", y = percentage, fill = habitat_group)) +geom_bar(stat ="identity", width =1) +coord_polar("y", start =0) +scale_fill_manual(values =c("Offshore/Pelagic"="#2166ac","Inshore/Reef"="#d6604d","Unknown"="#bababa","Variable/Coastal"="#92c5de")) +labs(fill ="Habitat", title ="B. Proportional representation") +theme_void() +theme(legend.position ="right") +geom_text(aes(label =paste0(percentage, "%")), position =position_stack(vjust =0.5))p_habitat <- p1 + p2# Save the combined plotsave_plot(p_habitat, "fig2_habitat_distribution", width =10, height =5)# Save individual panels as wellsave_plot(p1, "fig2a_habitat_bars", width =5, height =5)save_plot(p2, "fig2b_habitat_pie", width =5, height =5)# Display the plotp_habitat
Figure 2: Distribution of fish by generalized habitat zones
Show code
# Calculate effective sample sizes by habitathabitat_n <- habitat_grouped %>%mutate(interpretation =case_when( mni <5~"Too small for inference", mni <10~"Very limited inference", mni <20~"Limited inference",TRUE~"Moderate inference possible" ))# Save table as imagesave_table(habitat_n, "table2_habitat_stats", "Table 2: Statistical assessment by habitat zone")
Table 3: Statistical assessment of sample sizes by habitat zone
Habitat Zone
MNI
Percentage
Statistical Assessment
Inshore/Reef
10
35.7
Limited inference
Offshore/Pelagic
4
14.3
Too small for inference
Unknown
3
10.7
Too small for inference
Variable/Coastal
11
39.3
Limited inference
The assemblage shows mixed habitat exploitation, with no single zone dominating. All habitat categories have sample sizes too small for robust statistical inference.
3.4 Size Distribution
Show code
p_size <-ggplot(size_distribution, aes(x = size_category, y = mni)) +geom_bar(stat ="identity", fill ="#4575b4", alpha =0.8) +geom_text(aes(label = mni), vjust =-0.5, size =4) +labs(x ="Size Category", y ="MNI") +ylim(0, max(size_distribution$mni) *1.15) +theme(axis.text.x =element_text(angle =45, hjust =1))# Save the plotsave_plot(p_size, "fig3_size_distribution", width =8, height =5)# Display the plotp_size
Figure 3: Fish size distribution based on subjective size estimations
The size distribution shows predominance of small to medium specimens (8-20 inches), with few very large individuals. This pattern requires taphonomic evaluation before ecological interpretation.
4 Comparative Analysis: Early vs Late Deposits at Anakena
4.1 The Missing Comparison
While Martinsson-Wallin and Crockford (2002) claim to present data comparing early and late fish deposits, the tables provided in their paper show only early deposit data. However, Ayres (1985) provides the comparison they reference, with fish remains from both early (A.D. 1350-1500) and late (A.D. 1550-present) deposits at Anakena.
Table 4: Fish remains from early and late deposits at Anakena (Ayres 1985)
Fish Family
Early %
Early MNI
Late %
Late MNI
Muraenidae
30.5
18
20.0
27
Labridae
16.9
10
22.2
30
Unidentified
16.9
10
14.1
19
Serranidae
16.9
10
11.1
15
Diodontidae
5.1
3
5.9
8
Dasyatidae
0.0
0
7.4
10
Ostraciontidae
1.7
1
4.4
6
Holocentridae
1.7
1
4.4
6
Congridae
1.7
1
3.7
5
Brotulidae
3.4
2
2.2
3
Balistidae
1.7
1
2.2
3
Scaridae
3.4
2
1.5
2
Scorpaenidae
0.0
0
0.7
1
4.2 Visualizing the Comparison
Show code
# Prepare data for visualizationanakena_long <- anakena_comparison %>%select(Family, Early_MNI, Late_MNI) %>%pivot_longer(cols =c(Early_MNI, Late_MNI), names_to ="Period", values_to ="MNI") %>%mutate(Period =factor(str_replace(Period, "_MNI", ""),levels =c("Early", "Late")))# Create comparison plotp_comparison <-ggplot(anakena_long, aes(x =reorder(Family, MNI), y = MNI, fill = Period)) +geom_bar(stat ="identity", position ="dodge", alpha =0.8) +coord_flip() +scale_fill_manual(values =c("Early"="#d73027", "Late"="#4575b4"),labels =c("Early (1350-1500)", "Late (1550-present)")) +labs(x =NULL, y ="Minimum Number of Individuals",title ="Fish Taxa Changes at Anakena") +theme(legend.position ="bottom")# Save the plotsave_plot(p_comparison, "fig5_anakena_comparison", width =10, height =8)# Display the plotp_comparison
Figure 4: Comparison of fish family representation between early and late deposits at Anakena
4.3 Analysis of Changes
Show code
# Classify by general habitathabitat_classification <- anakena_comparison %>%mutate(Habitat =case_when( Family %in%c("Labridae", "Muraenidae", "Congridae", "Serranidae", "Scaridae", "Brotulidae") ~"Reef/Rocky", Family =="Dasyatidae"~"Sandy/Muddy", Family %in%c("Holocentridae", "Diodontidae", "Ostraciontidae","Balistidae", "Scorpaenidae") ~"Mixed Reef",TRUE~"Unknown" )) %>%group_by(Habitat) %>%summarise(Early_Total =sum(Early_MNI),Late_Total =sum(Late_MNI), .groups ='drop') %>%pivot_longer(cols =c(Early_Total, Late_Total),names_to ="Period",values_to ="MNI") %>%mutate(Period =str_replace(Period, "_Total", ""))# Create habitat comparisonp_habitat <-ggplot(habitat_classification, aes(x = Habitat, y = MNI, fill = Period)) +geom_bar(stat ="identity", position ="dodge", alpha =0.8) +scale_fill_manual(values =c("Early"="#d73027", "Late"="#4575b4")) +labs(x ="Habitat Type", y ="Total MNI",title ="Fish Habitat Representation Across Time") +theme(legend.position ="bottom")# Save and displaysave_plot(p_habitat, "fig6_habitat_persistence", width =8, height =6)p_habitat
Figure 5: Persistence of inshore fishing focus across time periods
4.4 Key Findings from the Anakena Comparison
The actual data from Ayres (1985) reveals:
No evidence of offshore fishing in either period: Both assemblages completely lack pelagic species (no Scombridae, Coryphaenidae, or other offshore taxa)
Consistent inshore focus: Both periods are dominated by reef-associated species (Labridae, Muraenidae, Serranidae)
Minor compositional changes:
Slight increase in Labridae (wrasses): 16.9% → 22.2%
Decrease in Serranidae (groupers): 16.9% → 11.1%
Appearance of Dasyatidae (rays) in late deposit (7.4%)
Sample size differences: Late deposit has 2.3× more specimens (135 vs 59 MNI), suggesting:
More intensive shelter use
Longer accumulation period
Better preservation conditions
NOT necessarily dietary change
The data directly contradicts claims of a shift from offshore to inshore fishing. Instead, it shows remarkable continuity in inshore fishing practices with minor variations that could reflect local environmental changes, fishing spot preferences, or taphonomic factors.
4.5 Comparing Different Depositional Environments
A fundamental issue undermining temporal comparisons is the dramatic change in depositional context between early and late periods. If late deposits represent rapid dune accumulation, they constitute an entirely different formation process.
Table 5: Depositional differences between early and late contexts
Factor
Early Deposits
Late Dune Deposits
Comparability
Deposition rate
Slow accumulation
Rapid accumulation
Not comparable
Sediment source
Mixed cultural/natural
Primarily aeolian
Not comparable
Energy environment
Low energy
High energy
Not comparable
Preservation potential
Higher
Lower
Biased
Activity representation
Primary disposal
Secondary/disturbed
Different activities
Spatial extent
Concentrated
Dispersed
Different scales
Temporal resolution
High (palimpsest)
Low (rapid burial)
Different processes
4.6 Taphonomic Effects on Assemblage Composition
Show code
# Create preservation probability modelscenario_data <-tibble(Period =rep(c("Early deposits\n(slow accumulation)", "Late deposits\n(rapid dunes)"), each =4),Fish_Type =rep(c("Large offshore", "Small offshore", "Large inshore", "Small inshore"), 2),Preservation_Probability =c(# Early deposits - better preservation overall0.7, 0.5, 0.6, 0.4,# Late deposits - size-biased preservation0.3, 0.1, 0.5, 0.2 ),Original_Catch =rep(c(30, 20, 25, 25), 2)) %>%mutate(Expected_Archaeological = Original_Catch * Preservation_Probability,Fish_Category =factor(Fish_Type, levels =c("Large offshore", "Small offshore","Large inshore", "Small inshore")))# Create visualizationp_preservation <-ggplot(scenario_data, aes(x = Fish_Category, y = Expected_Archaeological, fill = Period)) +geom_bar(stat ="identity", position ="dodge", alpha =0.8) +geom_hline(yintercept =5, linetype ="dashed", color ="red", alpha =0.5) +annotate("text", x =3.5, y =6, label ="Detection threshold", color ="red", size =3) +labs(x ="Fish Type",y ="Expected Archaeological Visibility\n(Original catch × Preservation probability)",fill ="Depositional Context") +scale_fill_manual(values =c("#4575b4", "#d73027")) +theme(legend.position ="bottom",axis.text.x =element_text(angle =45, hjust =1))# Save the plotsave_plot(p_preservation, "fig4_preservation_model", width =10, height =6)# Display the plotp_preservation
Figure 6: Model showing how identical fishing practices could produce different archaeological signatures due to depositional context
This model demonstrates how identical fishing behavior in both periods could produce an apparent shift from offshore to inshore species due solely to differential preservation in different depositional environments.
Show code
deposition_effects <-tibble(Aspect =c("Element size", "Element density", "Species representation","Spatial association", "Cultural behavior"),Effect =c("Small elements lost in rapid deposition","Light bones transported differently","Robust inshore species overrepresented","Mixing of unrelated deposits","Different disposal patterns"),`Impact on Interpretation`=c("Size bias against small fish","Density bias against bird/fish bones","False habitat shift pattern","Loss of behavioral context","Cannot infer subsistence change"))# Save table as imagesave_table(deposition_effects, "table4_taphonomic_effects", "Table 4: Taphonomic effects of rapid dune deposition")
quartz_off_screen
2
Show code
deposition_effects %>%kable(align ="lll") %>%kable_styling(bootstrap_options =c("striped"), full_width =TRUE) %>%column_spec(3, color ="darkred")
Table 6: Specific effects of rapid dune deposition on faunal assemblages
Aspect
Effect
Impact on Interpretation
Element size
Small elements lost in rapid deposition
Size bias against small fish
Element density
Light bones transported differently
Density bias against bird/fish bones
Species representation
Robust inshore species overrepresented
False habitat shift pattern
Spatial association
Mixing of unrelated deposits
Loss of behavioral context
Cultural behavior
Different disposal patterns
Cannot infer subsistence change
5 Discussion
5.1 Sample Size Limitations
With only 30 identified individuals, the early deposit sample lacks statistical power to characterize fishing practices, let alone detect temporal changes. The 26% identification rate further suggests significant information loss through poor preservation or analytical limitations.
5.2 Alternative Interpretations
Rather than representing baseline fishing practices, the observed patterns could reflect:
Opportunistic exploitation: Mixed offshore/inshore species suggest targeting seasonal aggregations rather than daily fishing patterns
Social deposition practices: Differential disposal based on status, ceremony, or specific events
Preservation biases: Systematic loss of smaller, more fragile elements
Sampling effects: Single site may not represent island-wide practices
5.3 The Depositional Context Problem
The comparison of early cultural deposits with late aeolian deposits violates basic principles of archaeological comparison. High-energy dune environments:
Preferentially destroy small, light elements (most fish bones)
Create size-sorted assemblages through winnowing
Mix materials from different sources and times
Break the relationship between behavior and archaeological patterning
Finding fewer offshore fish in late dune deposits provides no evidence for resource depletion when the assemblages are taphonomically incomparable.
6 Conclusions
The fish bone data from early Anakena deposits cannot support claims of temporal change in fishing practices or marine resource depletion. Critical issues include:
Inadequate sample sizes: 30 MNI from Martinsson-Wallin and Crockford is insufficient for robust analysis
No valid comparison: Their tables show only early deposit data, not the claimed comparison with late deposits
Taphonomic incomparability: Different depositional environments preclude direct comparison
Alternative explanations: Multiple non-ecological factors could produce observed patterns
Methodological overreach: Limited data interpreted through predetermined collapse narrative
When we examine the actual comparative data from Ayres (1985) for Anakena, we find: - No offshore fishing in either early or late periods - Consistent focus on inshore reef species across time - Minor variations in species proportions that do not indicate fundamental changes - Complete absence of pelagic species in both assemblages
The absence of deep-sea fish in late dune deposits cannot indicate changing fishing practices when: - The deposits themselves are fundamentally different in formation - Both early and late assemblages lack offshore species entirely - The “shift” from offshore to inshore fishing appears to be a narrative construction unsupported by data
Proper testing of the depletion hypothesis requires: - Comparable depositional contexts - Adequate sample sizes (minimum 100+ MNI per period) - Multiple sites across the island - Taphonomic controls and corrections - Independent environmental proxies - Integration with fishing technology data - Recognition that absence of offshore species may reflect technology/preference rather than depletion
Until these requirements are met, narratives of fishing depletion and ecological collapse remain unsupported speculation rather than demonstrated fact. The tendency to interpret limited archaeological data through collapse narratives should be replaced with more rigorous taphonomic and statistical analysis. The Anakena data, when properly examined, reveals continuity rather than collapse in marine subsistence practices.
7 References
Diamond, J. (2005). Collapse: How societies choose to fail or succeed. Viking Press.
Martinsson-Wallin, H., & Crockford, S. J. (2002). Early settlement of Rapa Nui (Easter Island). Asian Perspectives, 40(2), 244-278.
Steadman, D. W., Casanova, P. V., & Ferrando, C. C. (1994). Stratigraphy, chronology, and cultural context of an early faunal assemblage from Easter Island. Asian Perspectives, 33(1), 79-96.
8 Exported Figures and Tables
All figures and tables have been saved in the following directories:
PNG files: figures/png/
SVG files: figures/svg/
8.1 List of exported files:
Figures: - fig1_taxonomic_composition - Fish family representation by habitat - fig2_habitat_distribution - Combined habitat distribution plots - fig2a_habitat_bars - Habitat distribution bar chart - fig2b_habitat_pie - Habitat distribution pie chart - fig3_size_distribution - Fish size distribution - fig4_preservation_model - Differential preservation model