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Common ecology quantifies human insurgency


Many collective human activities, including violence, have been shown to exhibit universal patterns1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19. The size distributions of casualties both in whole wars from 1816 to 1980 and terrorist attacks have separately been shown to follow approximate power-law distributions6,7,9,10. However, the possibility of universal patterns ranging across wars in the size distribution or timing of within-conflict events has barely been explored. Here we show that the sizes and timing of violent events within different insurgent conflicts exhibit remarkable similarities. We propose a unified model of human insurgency that reproduces these commonalities, and explains conflict-specific variations quantitatively in terms of underlying rules of engagement. Our model treats each insurgent population as an ecology of dynamically evolving, self-organized groups following common decision-making processes. Our model is consistent with several recent hypotheses about modern insurgency18,19,20, is robust to many generalizations21, and establishes a quantitative connection between human insurgency, global terrorism10 and ecology13,14,15,16,17,22,23. Its similarity to financial market models24,25,26 provides a surprising link between violent and non-violent forms of human behaviour.

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Figure 1: Power-law exponents.
Figure 2: Size of events.
Figure 3: Timing of events.
Figure 4: Model framework for insurgency.

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  1. Gabaix, X., Parameswaran, G., Plerou, V. & Stanley, H. E. A theory of power law distributions in financial market fluctuations. Nature 423, 267–270 (2003)

    Article  ADS  CAS  Google Scholar 

  2. Lux, T. & Marchesi, M. Scaling and criticality in a stochastic multi-agent model of a financial market. Nature 397, 498–500 (1999)

    Article  ADS  CAS  Google Scholar 

  3. Dussutour, A., Fourcassie, V., Helbing, D. & Deneubourg, J. L. Optimal traffic organization in ants under crowded conditions. Nature 428, 70–73 (2004)

    Article  ADS  CAS  Google Scholar 

  4. Mantegna, R. N. & Stanley, H. E. Scaling behaviour in the dynamics of an economic index. Nature 376, 46–49 (1995)

    Article  ADS  CAS  Google Scholar 

  5. Barabasi, A. L. The origin of bursts and heavy tails in human dynamics. Nature 435, 207–211 (2005)

    Article  ADS  CAS  Google Scholar 

  6. Richardson, L. F. Variation of the frequency of fatal quarrels with magnitude. J. Am. Stat. Assoc. 43, 523–546 (1948)

    Article  Google Scholar 

  7. Cederman, L.-E. Modeling the size of wars: from billiard balls to sandpiles. Am. Polit. Sci. Rev. 97, 135–150 (2003)

    Article  Google Scholar 

  8. Lim, M., Metzler, R. & Bar-Yam, Y. Global pattern formation and ethnic/cultural violence. Science 317, 1540–1544 (2007)

    Article  ADS  CAS  Google Scholar 

  9. Clauset, A., Shalizi, C. R. & Newman, M. E. J. Power-law distributions in empirical data. SIAM Rev. 51, 661–703 (2009)

    Article  ADS  MathSciNet  Google Scholar 

  10. Clauset, A., Young, M. & Gleditsch, K. S. On the frequency of severe terrorist events. J. Conflict Resolut. 51, 58–87 (2007)

    Article  Google Scholar 

  11. Galam, S. & Mauger, A. On reducing terrorism power: a hint from physics. Physica A 323, 695–704 (2003)

    Article  ADS  Google Scholar 

  12. Johnson, N. et al. Universal patterns underlying ongoing wars and terrorism. Preprint at 〈〉 (2006)

  13. Johnson, D. D. P. & Madin, J. S. in Natural Security: A Darwinian Approach to a Dangerous World (eds Sagarin, R. & Taylor, T.) Ch. 11 159–185 (Univ. California Press, 2009)

    Google Scholar 

  14. Flack, J. Security in an uncertain world. Nature 453, 451–452 (2008)

    Article  ADS  CAS  Google Scholar 

  15. Adams, E. S. & Mesterton-Gibbons, M. Lanchester’s attrition models and fights among social animals. Behav. Ecol. 14, 719–723 (2003)

    Article  Google Scholar 

  16. Wrangham, R. W. in Emerging Synthesis in Science (ed. Pines, D.) 123–132 (Santa Fe Institute, 1985)

    Google Scholar 

  17. Epstein, J. M. Nonlinear Dynamics, Mathematical Biology, and Social Science (Addison-Wesley, 1997)

    MATH  Google Scholar 

  18. Robb, J. Brave New War: The Next Stage of Terrorism and the End of Globalization (Wiley, 2007)

    Google Scholar 

  19. Hammes, T. The Sling and the Stone: On War in the 21st Century (Zenith Press, 2004)

    Google Scholar 

  20. Packer, G. Knowing the enemy – can social scientists redefine the war on terror? New Yorker 18 December (2006)

  21. Ruszczycki, B., Burnett, B., Zhao, Z. & Johnson, N. F. Relating the microscopic rules in coalescence-fragmentation models to the macroscopic cluster-size distribution. Eur. Phys. J. B 10.1140/epjb/e2009-00354-5 (in the press)

  22. May, R. M. & McLean, A. R. Theoretical Ecology Principles and Applications 3rd edn (Oxford Univ. Press, 2007)

    MATH  Google Scholar 

  23. Couzin, I. D., Krause, J., Franks, N. R. & Levin, S. A. Effective leadership and decision making in animal groups on the move. Nature 433, 513–516 (2005)

    Article  ADS  CAS  Google Scholar 

  24. Eguiluz, V. M. & Zimmermann, M. G. Transmission of information and herd behaviour: an application to financial markets. Phys. Rev. Lett. 85, 5659–5662 (2000)

    Article  ADS  CAS  Google Scholar 

  25. D’Hulst, R. & Rodgers, G. J. Exact solution of a model for crowding and information transmission in financial markets. Int. J. Theor. Appl. Finance 3, 609–616 (2000)

    Article  MathSciNet  Google Scholar 

  26. Johnson, N. F., Jefferies, P. & Hui, P. M. Financial Market Complexity (Oxford Univ. Press, 2003)

    Book  Google Scholar 

  27. Spirling, A. The next big thing: scale invariance in political science. 〈〉.

  28. Palla, G., Barabási, A. L. & Vicsek, T. Quantifying social group evolution. Nature 446, 664–667 (2007)

    Article  ADS  CAS  Google Scholar 

  29. Hicks, M. H.-R. et al. The weapons that kill civilians — deaths of children and noncombatants in Iraq, 2003–2008. N. Engl. J. Med. 360, 1585–1588 (2009)

    Article  CAS  Google Scholar 

  30. Wang, W., Chen, Y. & Huang, J. Heterogeneous preferences, decision-making capacity, and phase transitions in a complex adaptive system. Proc. Natl Acad. Sci. USA 106, 8423–8428 (2009)

    Article  ADS  CAS  Google Scholar 

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We are grateful to J. Restrepo for his involvement in the data collection, and R. Zarama for discussions.

Author Contributions J.C.B., S.G., M.S. and N.F.J. worked on the data and data analysis. S.G., A.R.D. and N.F.J. worked on the model development. All authors participated in the writing and associated discussions, giving detailed feedback in all areas of the project.

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Correspondence to Neil F. Johnson.

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Bohorquez, J., Gourley, S., Dixon, A. et al. Common ecology quantifies human insurgency. Nature 462, 911–914 (2009).

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