Computational Model Library

Artificial Anasazi: Baseline Fixes, Dynamic Soil and Plot Crowding (1.0.0)

Artificial Anasazi is an agent-based model of farming households in the Long House Valley, Arizona, from 800 to 1350 CE. Each household chooses where to farm and settle based on expected harvest, water sources and stored maize, and simulated household counts are compared with the archaeological record.

This release adapts the NetLogo Models Library version (Stonedahl & Wilensky 2010) of Janssen’s (2009) NetLogo replication of the original Ascape model (Dean et al. 2000; Axtell et al. 2002). It contains four configurations in one NetLogo 7.0.4 file, selected with two switches:

  • Both switches off: the baseline, which is the Models Library model with small fixes that make it work as intended (the arable-uplands zone name, the setup base yield, the initial household count, one-tick-lag capacity reporting, and seed control with observation-only instruments).
  • soil-on?: dynamic soil quality that depletes under cultivation and regrows, following Janssen (2010, eq. 4).
  • crowding-on?: households may share an occupied plot, up to a limit, when no empty plot is available and their share still meets the nutrition need.
  • Both on: both mechanisms together.

Code comments mark each change as [BASELINE FIX], [BASELINE], [SOIL] or [CROWDING]. Standalone versions of each configuration, a project page and the full documentation are at the repository linked below.

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Release Notes

First release of this adaptation of Artificial Anasazi, built from the NetLogo Models Library version (Stonedahl & Wilensky 2010) of Janssen’s (2009) NetLogo replication and converted to NetLogo 7.0.4.

Baseline fixes (code comments tagged [BASELINE FIX] and [BASELINE])
- Arable-uplands zone name corrected in calculate-yield (uplands-fix?; OFF reproduces the published behavior).
- Optional application of harvest-adjustment to the setup base yield (setup-yield-fix?, default OFF).
- Initial household count is now assigned in setup.
- Carrying capacity is measured on the current tick; the published one-tick-lagged value is kept as potential-lagged.
- run-seed seeds the random number generator after clear-all. Fit statistics, peak windows and series run outside the main random stream, so they do not change a run.

Added mechanisms
- Dynamic soil quality (soil-on?, tag [SOIL]): depletion under cultivation and regrowth following Janssen (2010, eq. 4).
- Scarcity-driven plot sharing (crowding-on?, tag [CROWDING]): households join an occupied plot, up to crowding-limit, only when no empty plot is available and their share still meets the nutrition need.
- With both switches OFF the model reduces to the baseline.

Standalone versions of the baseline, soil-only and crowding-only models, a project page and further documentation are in the repository linked on this page.

Associated Publications

Artificial Anasazi: Baseline Fixes, Dynamic Soil and Plot Crowding 1.0.0

Submitted by Thomas Tuoti Published Oct 04, 2026 Last modified Oct 04, 2026
agent-based model agent-based modeling, NetLogo NetLogo Artificial Anasazi Anasazi Ancestral Puebloan Long House Valley archaeology socioecological systems carrying capacity soil degradation population collapse

Artificial Anasazi is an agent-based model of farming households in the Long House Valley, Arizona, from 800 to 1350 CE. Each household chooses where to farm and settle based on expected harvest, water sources and stored maize, and simulated household counts are compared with the archaeological record.

This release adapts the NetLogo Models Library version (Stonedahl & Wilensky 2010) of Janssen’s (2009) NetLogo replication of the original Ascape model (Dean et al. 2000; Axtell et al. 2002). It contains four configurations in one NetLogo 7.0.4 file, selected with two switches:

  • Both switches off: the baseline, which is the Models Library model with small fixes that make it work as intended (the arable-uplands zone name, the setup base yield, the initial household count, one-tick-lag capacity reporting, and seed control with observation-only instruments).
  • soil-on?: dynamic soil quality that depletes under cultivation and regrows, following Janssen (2010, eq. 4).
  • crowding-on?: households may share an occupied plot, up to a limit, when no empty plot is available and their share still meets the nutrition need.
  • Both on: both mechanisms together.

Code comments mark each change as [BASELINE FIX], [BASELINE], [SOIL] or [CROWDING]. Standalone versions of each configuration, a project page and the full documentation are at the repository linked below.

Release Notes

First release of this adaptation of Artificial Anasazi, built from the NetLogo Models Library version (Stonedahl & Wilensky 2010) of Janssen’s (2009) NetLogo replication and converted to NetLogo 7.0.4.

Baseline fixes (code comments tagged [BASELINE FIX] and [BASELINE])
- Arable-uplands zone name corrected in calculate-yield (uplands-fix?; OFF reproduces the published behavior).
- Optional application of harvest-adjustment to the setup base yield (setup-yield-fix?, default OFF).
- Initial household count is now assigned in setup.
- Carrying capacity is measured on the current tick; the published one-tick-lagged value is kept as potential-lagged.
- run-seed seeds the random number generator after clear-all. Fit statistics, peak windows and series run outside the main random stream, so they do not change a run.

Added mechanisms
- Dynamic soil quality (soil-on?, tag [SOIL]): depletion under cultivation and regrowth following Janssen (2010, eq. 4).
- Scarcity-driven plot sharing (crowding-on?, tag [CROWDING]): households join an occupied plot, up to crowding-limit, only when no empty plot is available and their share still meets the nutrition need.
- With both switches OFF the model reduces to the baseline.

Standalone versions of the baseline, soil-only and crowding-only models, a project page and further documentation are in the repository linked on this page.

Cite this Model

Thomas Tuoti (2026, October 04). “Artificial Anasazi: Baseline Fixes, Dynamic Soil and Plot Crowding” (Version 1.0.0). CoMSES Computational Model Library. Retrieved from: https://www.comses.net/codebases/d24a7b91-7c5a-4acb-83ad-f9a947086691/releases/1.0.0/

Replication of a previously described model

Janssen, M. (2013, April 27). “Artificial Anasazi” (Version 1.1.0). CoMSES Computational Model Library. https://doi.org/10.25937/krp4-g724

References

Axtell, R. L., Epstein, J. M., Dean, J. S., Gumerman, G. J., Swedlund, A. C., Harburger, J., Chakravarty, S., Hammond, R., Parker, J., & Parker, M. (2002). Population growth and collapse in a multiagent model of the Kayenta Anasazi in Long House Valley. Proceedings of the National Academy of Sciences 99(suppl 3): 7275-7279.

Dean, J. S., Gumerman, G. J., Epstein, J. M., Axtell, R. L., Swedlund, A. C., Parker, M. T., & McCarroll, S. (2000). Understanding Anasazi culture change through agent-based modeling. In T. A. Kohler & G. J. Gumerman (Eds.), Dynamics in Human and Primate Societies (pp. 179-205). Oxford University Press.

Janssen, M. A. (2009). Understanding Artificial Anasazi. Journal of Artificial Societies and Social Simulation 12(4): 13.

Janssen, M. A. (2010). Population aggregation in ancient arid environments. Ecology and Society 15(2): 19.

Stonedahl, F., & Wilensky, U. (2010). NetLogo Artificial Anasazi model. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

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Contributors
Thomas Tuoti
External Repository
github.com/well-noted/Artificial-Anasazi
Input Data
github.com/well-noted/Artificial-Anasazi/tree/combined/data
DOI
No assigned DOI
Model Version
1.0.0
License
GPL-2.0
Programming Language
NetLogo 7.0.4
Software Framework
agent-based modeling, NetLogo
Operating System
Operating System Independent
Publish Date
Sunday, October 04, 2026
Last Updated
Sunday, October 04, 2026
Downloads 0
Peer Review
Unreviewed
Version Submitter First published Last modified Status
1.0.0 Thomas Tuoti Sun Oct 4 15:38:36 2026 Sun Oct 4 15:38:39 2026 Published

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