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Altruism through beard chromodynamics

Nature volume 440, pages 663666 (30 March 2006) | Download Citation



The evolution of altruism, a behaviour that benefits others at one's own fitness expense, poses a darwinian paradox. The paradox is resolved if many interactions are with related individuals so that the benefits of altruism are reaped by copies of the altruistic gene in other individuals1, a mechanism called kin selection2. However, recognition of altruists could provide an alternative route towards the evolution of altruism1,3,4,5. Arguably the simplest recognition system is a conspicuous, heritable tag, such as a green beard1,3. Despite the fact that such genes have been reported6,7,8, the ‘green beard effect’3 has often been dismissed because it is unlikely that a single gene can code for altruism and a recognizable tag1,3,9. Here we model the green beard effect and find that if recognition and altruism are always inherited together, the dynamics are highly unstable, leading to the loss of altruism. In contrast, if the effect is caused by loosely coupled separate genes, altruism is facilitated through beard chromodynamics in which many beard colours co-occur. This allows altruism to persist even in weakly structured populations and implies that the green beard effect, in the form of a fluid association of altruistic traits with a recognition tag, can be much more prevalent than hitherto assumed.

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We thank P. Credland for his encouragement and comments on the manuscript. Author Contributions Both authors contributed equally to this paper. V.A.A.J. formulated and analysed the mathematical model; M.v.B. formulated and analysed the simulation model.

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  1. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK

    • Vincent A. A. Jansen
  2. Laboratoire d'Ecologie ENS/UPMC/CNRS, UMR 7625, Université Pierre et Marie Curie, Bâtiment A, 7ème Etage, CC 237, 7 quai St Bernard, 75252 Paris Cedex 05, France

    • Minus van Baalen


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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Corresponding author

Correspondence to Vincent A. A. Jansen.

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