1

2 Supplementary Information for

3 Bayesian time-series analyses reveal a complex impact of climate change on Classic Maya

4 conflict

5 W. Christopher Carleton, Dave Campberll, and Mark Collard

6 Mark Collard 7 E-mail: [email protected]

8 This PDF file includes:

9 Supplementary text 10 Fig. S1 11 Tables S1 to S2 12 References for SI reference citations

W. Christopher Carleton, Dave Campberll, and Mark Collard 1 of 11 13 Supporting Information Text

14 The Conflict Data. Compiled from the published literature (1–4), the conflict record contains information about 144 conflict 15 events that occurred between approximately 290 and 900 CE. The events were recorded on monuments in more than 30 Classic 16 Maya urban centers described in dozens of scholarly works (Table S1)—see Kennett et al.’s (2) supplementary information 17 for a complete bibliography of the conflicts they included. These events include general attacks, captive taking, beheadings, 18 defacement of monuments, and “Star Wars”, which were large inter-polity conflicts timed to accord with certain celestial 19 alignments (5). 20 We had to “clean” the conflict data to account for missing information in some cases. For a given conflict, most scholars 21 listed a Classic Maya calendar date along with a corresponding Gregorian date for both the event and for the erection of 22 monument on which it was recorded. They also often provided one or two archaeological site names, and some text describing 23 the type of conflict (Table S1). However, there were three kinds of missing data that needed to be accounted for. One involved 24 missing Gregorian translations of Classic Maya dates. In a few cases, authors provided only Classic Maya dates for events and 25 monuments. To account for this, we calculated the Gregorian date using the standard translation method (6). The second kind 26 of missing information involved undated conflict events or monuments. In the former case we used the relevant monument date 27 for the undated conflict, while in the latter we used the available conflict date for the corresponding missing monument date. 28 The cumulative effect of these adjustments was to make the conflict and monument records correlate more closely, which in 29 turn meant that our analysis was more conservative regarding the potential impact of climate change. 30 We also attempted to eliminate duplicate references to conflict events. Since we gathered conflict events from multiple 31 sources in the academic literature, it is possible that duplicates would occur because there was not always sufficient information 32 to determine whether different authors were referring the same event. To account for these potential duplicates, we combed 33 through the records and compared site names, descriptions, and Classic Maya calendar dates between conflicts dated to the 34 same Gregorian year. When a potential duplicate was identified, we eliminated it from our list of conflicts—the eliminated 35 events are identified in Table S1 by a “1” in the “likely duplicate” column.

36 Interaction effects. In our analysis of the Late Classic period data, we determined that both temperature and rainfall likely 37 had an impact on conflict levels, but these effects could have been moderated by an interaction between the climate variables. 38 We called the model containing both variables Combined. That model outperformed the others in our Late Classic analysis 39 according to a comparison of the relevant Bayes Factors. The effects of each variable, though, could be moderated by the 40 level of the other variable—i.e., there might have been interacting in a way that would complicate our interpretations. To 41 test for an interaction effect, we created an additional model in which we included an interaction term—a model we termed 42 Interaction. We then compared the Bayes Factor of Interaction to the Bayes Factor of Combined and the other models in 43 the Late Classic period analysis (see Table S2). If there was an interaction effect, we reasoned, Interaction would outperform 44 Combined. According to our results, however, this was not the case—the interaction model did not outperform Combined. 45 Consequently, there is no evidence that an interaction effect was present and the effects of rainfall and temperature in Combined 46 can be interpreted independently of one another.

Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates Stela 02 737 Kennet et al. 2012 Lintel 04 603 Kennet et al. 2012 Bonampak Column 715 Kennet et al. 2012 Bonampak Lintel 03 741 Kennet et al. 2012 Bonampak Lintel 01 787 Kennet et al. 2012 Bonampak Lintel 02 792 Kennet et al. 2012 Altar 21 Mutal () 556 Kennet et al. 2012 Caracol B16 Stucco 626 Kennet et al. 2012 Caracol Stela 03 627 Kennet et al. 2012 Caracol Stela 03 Naranjo 632 Kennet et al. 2012

2 of 11 W. Christopher Carleton, Dave Campberll, and Mark Collard Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates Caracol Altar 23 801 Kennet et al. 2012 Caracol Altar 12 Mutal (Tikal) 820 Kennet et al. 2012 Caracol Altar 12 Mutal (Tikal) 820 Kennet et al. 1 2012 Caracol Altar 12 820 Kennet et al. 1 2012 Casa Col- 870 Kennet et al. orada frieze 2012 Chichen Itza Las Monjas 880 Kennet et al. 2012 Chichen Itza Las Monjas 880 Kennet et al. 1 2012 Chichen Itza Temple of the 881 Kennet et al. Four Lintels 2012 Lintel 02 Chinikiha Throne 574 Kennet et al. 2012 HS 04, Step 4 648 Kennet et al. 2012 Dos Pilas HS 02 east, Mutal (Tikal) 657 Kennet et al. Step 04 2012 Dos Pilas HS 02 east, 664 Kennet et al. Step 01 2012 Dos Pilas HS 02 east, 664 Kennet et al. 1 Step 01 2012 Dos Pilas HS 02 west, 678 Kennet et al. Step 04 2012 Dos Pilas HS 04, Step 3 678 Kennet et al. 2012 Dos Pilas HS 02 west, 679 Kennet et al. Step 03 2012 Dos Pilas HS 02 west, 679 Kennet et al. 1 Step 03 2012 Dos Pilas HS 04, Step 5 679 Kennet et al. 1 2012 Dos Pilas Stela 02 736 Kennet et al. 2012 Dos Pilas Stela 02 736 Kennet et al. 2012 Dos Pilas Stela 02 736 Kennet et al. 1 2012 Stela 17 746 Kennet et al. 2012 Itzan Stela 17 768 Kennet et al. 2012 Itzan Stela 17 768 Kennet et al. 1 2012 Itzan Stela 17 781 Kennet et al. 2012 Stela 02 780 Kennet et al. 2012 Ixkun Stela 02 780 Kennet et al. 2012 Altar 01 880 Kennet et al. 2012

W. Christopher Carleton, Dave Campberll, and Mark Collard 3 of 11 Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates HS 01, Block 805 Kennet et al. 04 2012 La Mar Stela 03 794 Kennet et al. 2012 La Mar Stela 03 794 Kennet et al. 2012 La Pasadita Lintel 01 759 Kennet et al. 2012 Laxtunich Lintel 01 784 Kennet et al. 2012 Laxtunich Lintel 01 784 Kennet et al. 2012 Laxtunich Lintel 01 784 Kennet et al. 1 2012 Stela 02 801 Kennet et al. 2012 Naranjo Stela 28 720 Kennet et al. No event date was 2012 provided. The mon- ument date was used instead. Naranjo Stela 35 801 Kennet et al. No event date was 2012 provided. The mon- ument date was used instead. Naranjo Stela 22 693 Kennet et al. 2012 Naranjo Stela 22 693 Kennet et al. 1 2012 Naranjo Stela 22 694 Kennet et al. 2012 Naranjo Stela 22 694 Kennet et al. 2012 Naranjo Stela 22 694 Kennet et al. 1 2012 Naranjo Stela 22 Mutal (Tikal) 695 Kennet et al. 2012 Naranjo Stela 22 Mutal (Tikal) 695 Kennet et al. 1 2012 Naranjo Stela 22 Ucanal 696 Kennet et al. 2012 Naranjo Stela 22 Mutal (Tikal) 699 Kennet et al. 2012 Naranjo Stela 24 699 Kennet et al. 2012 Naranjo Stela 23 710 Kennet et al. 2012 Naranjo Stela 23 711 Kennet et al. 2012 Naranjo Stela 02 713 Kennet et al. 2012 Naranjo Stela 30 715 Kennet et al. 2012 Naranjo Stela 13 775 Kennet et al. 2012 Naranjo Stela 12 Yaxha 799 Kennet et al. 2012

4 of 11 W. Christopher Carleton, Dave Campberll, and Mark Collard Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates Naranjo Stela 12 799 Kennet et al. 1 2012 Naranjo Stela 12 799 Kennet et al. 2012 Naranjo Stela 12 799 Kennet et al. 2012 Naranjo Stela 12 Yaxha 800 Kennet et al. 2012 Naranjo Stela 12 800 Kennet et al. 2012 Naranjo Stela 11 597 Kennet et al. 2012 House C HS 599 Kennet et al. 2012 Palenque Tablet, east 611 Kennet et al. panel 2012 Palenque House C HS Mutal (Tikal) 659 Kennet et al. 2012 Palenque Tablet, mid- 672 Kennet et al. dle panel 2012 Palenque Tablet of the 724 Kennet et al. Slaves 2012 Palenque Tablet of the 725 Kennet et al. Slaves 2012 Palenque Tablet of the Kol 729 Kennet et al. Slaves 2012 Palenque Pier A 690 Kennet et al. No event date was 2012 provided. The mon- ument date was used instead. Palenque Tablet of Tem- 688 Kennet et al. No event date was ple 17 2012 provided. The mon- ument date was used instead. Piedras Ne- Lintel 04 631 Kennet et al. gras 2012 Piedras Ne- Throne 01 780 Kennet et al. gras 2012 Piedras Ne- Throne 01 781 Kennet et al. gras 2012 Piedras Ne- Stela 12 788 Kennet et al. gras 2012 Quirigua Monument 787 Kennet et al. 23/Altar O’ 2012 Quirigua Monument 790 Kennet et al. 23/Altar O’ 2012 Seibal Tablet 04 746 Kennet et al. 2012 HS 02, Step 3 761 Kennet et al. 2012 Tamarindito HS 02, Step 3 761 Kennet et al. 2012 Tikal Stela 04 379 Kennet et al. 2012 Tikal Stela 18 396 Kennet et al. 2012

W. Christopher Carleton, Dave Campberll, and Mark Collard 5 of 11 Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates Tikal Seated Figure 406 Kennet et al. from Str. 3D- 2012 43 Tikal Ballcourt 414 Kennet et al. marker 2012 Tikal Stela 01 451 Kennet et al. 2012 Tikal Temple I Lin- 696 Kennet et al. tel 03 2012 Tikal Temple I Lin- 696 Kennet et al. 1 tel 03 2012 Tikal Temple IV Yaxha 744 Kennet et al. Lintel 03 2012 Tonin^ Monument 699 Kennet et al. No event date was 141 2012 provided. The mon- ument date was used instead. Tortuguero Monument 644 Kennet et al. 06 (T Shaped 2012 Tablet) Tortuguero Monument 645 Kennet et al. 06 (T Shaped 2012 Tablet) Tortuguero Monument Yompi 649 Kennet et al. 06 (T Shaped 2012 Tablet) Tortuguero Monument 8 650 Kennet et al. (Sarcophag 2012 us) Tortuguero Monument 8 650 Kennet et al. (Sarcophag 2012 us) Tortuguero Monument 650 Kennet et al. 06 (T Shaped 2012 Tablet) Tortuguero Monument 8 650 Kennet et al. 1 (Sarcophag 2012 us) Tortuguero Jade Earflare 656 Kennet et al. 2012 Yaxchilan HS 03, Step 1 513 Kennet et al. 2012 Yaxchilan HS 03, Step 1 662 Kennet et al. 2012 Yaxchilan Lintel 46 662 Kennet et al. 1 2012 Yaxchilan Stela 20 662 Kennet et al. 1 2012 Yaxchilan HS 03, Step 1 677 Kennet et al. 2012 Yaxchilan HS 03, Step 1 677 Kennet et al. 1 2012 Yaxchilan Stela 19 681 Kennet et al. 2012 Yaxchilan HS 03, Step 3 681 Kennet et al. 2012

6 of 11 W. Christopher Carleton, Dave Campberll, and Mark Collard Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates Yaxchilan HS 03, Step 3 681 Kennet et al. 2012 Yaxchilan Lintel 45 681 Kennet et al. 1 2012 Yaxchilan Stela 15 681 Kennet et al. 1 2012 Yaxchilan HS 03, Step 3 682 Kennet et al. 2012 Yaxchilan Lintel 44 690 Kennet et al. 2012 Yaxchilan HS 03, Step 6 698 Kennet et al. 2012 Yaxchilan HS 03, Step 2 708 Kennet et al. 2012 Yaxchilan Stela 18 729 Kennet et al. 2012 Yaxchilan HS 04, Step 3 752 Kennet et al. 2012 Yaxchilan HS 04, Step 3 752 Kennet et al. 1 2012 Yaxchilan Lintel 16 752 Kennet et al. 1 2012 Yaxchilan Lintel 08 755 Kennet et al. 2012 Yaxchilan HS 05 797 Kennet et al. 2012 Yaxchilan HS 05 799 Kennet et al. 2012 Yaxchilan HS 05 800 Kennet et al. 2012 Yaxchilan Lintel 10 808 Kennet et al. 2012 Tikal Caracol 556 Chase and Chase 2003 Caracol Tikal 562 Chase and Chase 2003 Yaxchilan Lacanha 564 Chase and Chase 2003 Caracol Naranjo 626 Chase and Chase 2003 Caracol Naranjo 627 Chase and Chase 2003 Caracol Naranjo 631 Chase and Chase 2003 Caracol Naranjo 636 Chase and Chase 2003 Palenque Site Q 654 Chase and Chase 2003 Palenque Yaxchilan 659 Chase and Chase 2003 Dos Pilas Machaquila 664 Chase and Chase 2003 Dos Pilas Tikal 670 Chase and Chase 2003 Tikal Dos Pilas 672 Chase and Chase 2003

W. Christopher Carleton, Dave Campberll, and Mark Collard 7 of 11 Table S1. Classic Maya Conflict Data.

Monument Monument Site(s) Site(s) Greg- Reference Notes Likely Location Named Named orian Dupli- Year cates Site Q Tikal 677 Chase and Chase 2003 Naranjo Caracol 680 Chase and Chase 2003 Naranjo Ucanal 693 Chase and Chase 2003 Naranjo Tikal 695 Chase and Chase 2003 Tikal Site Q 695 Chase and Chase 2003 Tikal El Peru 695 Schele and Matthews 1991 Naranjo Ucanal 698 Schele and Matthews 1991 Dos Pilas Tikal 705 Chase and Chase 2003 Tonina Palenque 711 Schele and Matthews 1991 Tonina Palenque 711 Chase and Chase 2003 Yaxchilan Lacanha 729 Chase and Chase 2003 Dos Pilas Seibal 735 Chase and Chase 2003 Quirigua Copan 738 Chase and Chase 2003 Aguateca Cancuen 741 Chase and Chase 2003 Machaquila Motul de San 741 Chase and Jose Chase 2003 Tikal Yaxha 743 Chase and Chase 2003 Tikal Motul de San 744 Chase and Jose Chase 2003 Dos Pilas Yaxchilan 751 Chase and Chase 2003 Aguateca El Chorro 771 Chase and Chase 2003 La Mar Pomona 774 Chase and Chase 2003 Yaxchilan 782 Schele and Matthews 1991 Piedras Ne- Pomona 787 Chase and gras Chase 2003 Piedras Ne- Pomona 794 Chase and gras Chase 2003 Caracol Ucanal 800 Chase and Chase 2003 Caracol Tikal 819 Chase and Chase 2003

8 of 11 W. Christopher Carleton, Dave Campberll, and Mark Collard Table S2. Interaction Model Results. This table contains the primary model results for the interaction effect analysis involving data from the Late Classic period (600-900 CE). According to the Bayes Factors, including an interaction effect between the temperature and rainfall covariates did not improve the model—i.e., Combined was still the most probable model given the data.

Model Posterior Prob. Bayes Temp. Rain. Factor Coef. Coef. Tit-for-tat 3.60E-83 1.00 Temperature 1.10E-82 3.11 0.49 Rainfall 3.10E-83 0.87 -0.86 Combined 6.00E-82 16.74 0.33 -0.88 Interact 3.23E-82 9.02 0.66 -0.9

W. Christopher Carleton, Dave Campberll, and Mark Collard 9 of 11 Fig. S1. Autocorrelation in annual Classic Maya conflict

10 of 11 W. Christopher Carleton, Dave Campberll, and Mark Collard 47 References

48 1. Hassig R (1992) War and Society in Ancient MesoAmerica. (University of California Press, Berkeley), p. 347. 49 2. Kennett DJ, et al. (2012) Development and disintegration of maya political systems in response to climate change. Science 50 338(6108):788–791. 51 3. Schele L, Mathews P (1991) Royal visits and other intersite relationships among the Classic Maya in Classic Maya Political 52 History: Hieroglyphic and Archaeological Evidence, ed. Culbert TP. (Cambridge University Press), pp. 226–252. 53 4. Chase DZ, Chase AF (2003) Texts and Contexts in Maya Warfare: A Brief Consideration of Epigraphy and Archaeology 54 at Caracol, Belize in Ancient Mesoamerican Warfare, eds. Brown M, Stanton T. (Alta Mira Press, Walnut Creek), pp. 55 171–188. 56 5. Webster D (2000) The not so peaceful civilization: A review of Maya war. Journal of World Prehistory 14(1):65–119. 57 6. Kennett DJ, et al. (2013) Correlating the Ancient Maya and Modern European Calendars with High-Precision AMS (14)C 58 Dating. Scientific Reports 3:1597.

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