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Open Access Research article

The evolution of prompt reaction to adverse ties

Sven Van Segbroeck126, Francisco C Santos26, Ann Nowé1, Jorge M Pacheco36 and Tom Lenaerts456*

Author Affiliations

1 COMO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium

2 IRIDIA, CoDE, Université Libre de Bruxelles, Avenue Franklin Roosevelt 50, 1050 Brussels, Belgium

3 ATP-group, CFTC and Departamento de Fisica da Faculdade de Ciências, P-1649-003 Lisboa Codex, Portugal

4 ML-group, Département d'Informatique, Université Libre de Bruxelles, Boulevard du Triomphe CP212, 1050 Brussels, Belgium

5 SWITCH, VIB, Pleinlaan 2, 1050 Brussels, Belgium

6 GADGET, Apartado 1329, 1009-001 Lisboa, Portugal

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BMC Evolutionary Biology 2008, 8:287  doi:10.1186/1471-2148-8-287

Published: 17 October 2008



In recent years it has been found that the combination of evolutionary game theory with population structures modelled in terms of dynamical graphs, in which individuals are allowed to sever unwanted social ties while keeping the good ones, provides a viable solution to the conundrum of cooperation. It is well known that in reality individuals respond differently to disadvantageous interactions. Yet, the evolutionary mechanism determining the individuals' willingness to sever unfavourable ties remains unclear.


We introduce a novel way of thinking about the joint evolution of cooperation and social contacts. The struggle for survival between cooperators and defectors leads to an arms race for swiftness in adjusting social ties, based purely on a self-regarding, individual judgement. Since defectors are never able to establish social ties under mutual agreement, they break adverse ties more rapidly than cooperators, who tend to evolve stable and long-term relations. Ironically, defectors' constant search for partners to exploit leads to heterogeneous networks that improve the survivability of cooperators, compared to the traditional homogenous population assumption.


When communities face the prisoner's dilemma, swift reaction to adverse ties evolves when competition is fierce between cooperators and defectors, providing an evolutionary basis for the necessity of individuals to adjust their social ties. Our results show how our innate resilience to change relates to mutual agreement between cooperators and how "loyalty" or persistent social ties bring along an evolutionary disadvantage, both from an individual and group perspective.