Altruism through beard chromodynamics (original) (raw)

Nature volume 440, pages 663–666 (2006)Cite this article

Abstract

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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Figure 1: The level of cooperation in the population in the approach to the heteroclinic cycle.

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Figure 2: Evolution of cooperation and beard colour diversity.

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Figure 3: An example of a snapshot of spatial beard chromodynamics.

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Figure 4: Cooperation and diversity versus viscosity.

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Acknowledgements

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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Authors and Affiliations

  1. School of Biological Sciences, Royal Holloway, University of London, TW20 0EX, Surrey, Egham, 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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  1. Vincent A. A. Jansen
  2. Minus van Baalen

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Correspondence toVincent A. A. Jansen.

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Jansen, V., van Baalen, M. Altruism through beard chromodynamics.Nature 440, 663–666 (2006). https://doi.org/10.1038/nature04387

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Editorial Summary

How green is your beard?

The evolution of altruism, especially as directed to non-kin, is an enigma of evolutionary biology. Explanations would come easier, however, if altruists were readily recognized. Arguably the simplest recognition system is a conspicuous, heritable tag. A green beard would do it. A few examples of the ‘green beard effect’ have been reported in human interactions, though beards per se and greenness tend not to feature. A problem with this explanation is the improbability of one gene encoding all three functions (altruism, tag and recognition). Based on modelling, Jansen and van Baalen identify a further problem with this theory: even if green beard genes can be selectively advantageous, altruism is unstable under previous assumptions. But, they add, the evolution of cooperation using a recognition mechanism may be more likely if many beard colours coexist.