Human Nature

, Volume 23, Issue 1, pp 68–88

Hormonal Mechanisms for Regulation of Aggression in Human Coalitions

  • Mark V. Flinn
  • Davide Ponzi
  • Michael P. Muehlenbein

DOI: 10.1007/s12110-012-9135-y

Cite this article as:
Flinn, M.V., Ponzi, D. & Muehlenbein, M.P. Hum Nat (2012) 23: 68. doi:10.1007/s12110-012-9135-y


Coalitions and alliances are core aspects of human behavior. All societies recognize alliances among communities, usually based in part on kinship and marriage. Aggression between groups is ubiquitous, often deadly, fueled by revenge, and can have devastating effects on general human welfare. Given its significance, it is surprising how little we know about the neurobiological and hormonal mechanisms that underpin human coalitionary behavior. Here we first briefly review a model of human coalitionary behavior based on a process of runaway social selection. We then present several exploratory analyses of neuroendocrine responses to coalitionary social events in a rural Dominican community, with the objective of understanding differences between in-group and out-group competition in adult and adolescent males. Our analyses indicate: (1) adult and adolescent males do not elevate testosterone when they defeat their friends, but they do elevate testosterone when they defeat outsiders; (2) pre-competition testosterone and cortisol levels are negatively associated with strength of coalitionary ties; and (3) adult males usually elevate testosterone when interacting with adult women who are potential mates, but in a striking reversal, they have lower testosterone if the woman is a conjugal partner of a close friend. These naturalistic studies hint that reciprocity, dampening of aggression, and competition among friends and allies may be biologically embedded in unique ways among humans.


Coalitions Aggression Human biology Evolution Hormone Testosterone Neuroendocrine Cooperation 

Copyright information

© Springer Science + Business Media, LLC 2012

Authors and Affiliations

  • Mark V. Flinn
    • 1
  • Davide Ponzi
    • 2
  • Michael P. Muehlenbein
    • 3
  1. 1.Department of AnthropologyUniversity of MissouriColumbiaUSA
  2. 2.Division of Biological SciencesUniversity of MissouriColumbiaUSA
  3. 3.Department of AnthropologyIndiana UniversityBloomingtonUSA

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