Friday, 4 November 2011

Hamilton on group/kin selection

A paper by W.D. Hamilton called "Innate Social Aptitudes of Man: an approach from evolutionary genetics" has been originally published in 1975 by editor Robin Fox (Biosocial Anthropology. London: Malaby Press, pp. 133-153) and has been reprinted in W. D. Hamilton (1996. Narrow Roads of Gene Land. Oxford: W.H. Freeman, pp. 329-351). It has been cited for very different reasons. 

On the one hand, Robert Trivers has called it Hamilton's "fascist paper" thus mocking the shocked reactions of some anthropologists to the paper. These reactions turned against the part of the paper headed "Tribal Facies of Social Behaviour," where Hamilton tried to draw conclusions from his modelling for human behaviour and argued that morally bad streaks from xenophobia to warfare may have a genetic basis that can be positively selected in a group structured species. For example:
"It has been argued that warfare must be a pathological development in humans, continually countered by natural selection, and this claim is sometimes based on a sweeping a priori view that habits of mortal intraspecific fighting must always endanger the survival of a species. [reference to Lorenz 1966. On Aggression.] While endorsing such a view as regards wars between the few frightfully armed superpowers of today, I see no likelihood for it as regards fighting of individuals or of groups up to the level of small nations. Of course, for the species as a whole, and in the short term, war is detrimental from the biological demographic point of view, but, as shown above and elsewhere, detriment to the species does not mean that a genetical proclivity will not spread. Anyway, what is bad at one level may be good at another and the cost to the species may by paid in the long run. The gross inefficiency of warfare may be just what is necessary, or at least an alternative to birth control and infanticide, in order to spare a population's less resilient resources from dangerous exploitation. Maybe if the mammoth-hunters had attacked each other more and the mammoths less they could be mammoth-hunters still." (Hamilton 1975, see also 1996, p. 334f)
Later citations were less shocked about or interested in the stark conclusions at the end of the paper and centered on the earlier parts of the paper, for example, the following passage:
"Returning to the problem of units of selection, Darwin himself, vague about the process of heredity, based most of his arguments on considerations of the fitness of individuals. He made occasional exceptions, as for the social insects where he treated the 'family group' as the unit of selection. I believe even these limited concessions were incautious (Hamilton 1972), and value his judgement more where, discussing the evolution of courage and self-sacrifice in man, he left a difficulty apparent and unresolved. He saw that such traits would naturally be counter-selected within a social group whereas in competition between groups the groups with the most of such qualities would be the ones best fitted to survive and increase. This open problem which Darwin left is really the starting-point of my own argument, but it is historically interesting to note that after some initial wavering between the calls of Spencer, Kropotkin, and others, almost the whole field of biology stampeded in the direction where Darwin had gone circumspectly or not at all." (Hamilton 1975, p. 134f; see also 1996, p. 330f)
[The passages that Hamilton refers to, where Darwin speculated about the good of the insect community or about between-tribe selection, can be found here.] 

In The Extended Phenotype, Richard Dawkins (1983, p. 6) quoted the last sentence with the stampede metaphor to suggest that Hamilton rejected group selection. 

More recently, still, the same paper has been cited as evidence that, with the help of the Price equation, Hamilton reconsidered and eventually accepted group selection as a live possibility (e.g. Sober and Wilson 1998, p. 71ff; Segerstrale 2000, p. 53ff).

IMHO, Hamilton best explained his conception of the relation between group selection, kin selection, and inclusive fitness in the following passage:
"The usefulness of the 'inclusive fitness' approach to social behaviour (i.e. an approach using criteria like (bABK - k) > 0) is that it is more general than the 'group selection', 'kin selection', or 'reciprocal altruism' approaches and so provides an overview even where regression coefficients and fitness effects are not easy to estimate or specify. As against 'group selection' it provides a useful conceptual tool where no grouping is apparent—for example, it can deal with an ungrouped viscous population where, owing to restricted migration, an individual's normal neighbours and interactants tend to be his genetical kindred.    
Because of the way it was first explained, the approach using inclusive fitness has often been identified with 'kin selection' and presented strictly as an alternative to 'group selection' as a way of establishing altruistic social behaviour by natural selection (e.g. Maynard Smith 1964; Lewontin 1970). But the foregoing discussion shows that kinship should be considered just one way of getting positive regression of genotype in the recipient, and that it is this positive regression that is vitally necessary for altruism. Thus the inclusive-fitness concept is more general than ‘kin selection’.” (Hamilton 1975, p. 140f; see also 1996, p. 336f)

Hamilton's hierarchy of concepts seems to be:
general theory: inclusive fitness
   special cases: group selection, kin selection, reciprocity, etc.

But it seems to be significant that, in drawing conclusions from his new insight into the real possibility that between-group selection can override within-group selection in structured populations, he emphasized the dark side of between-group xenophobia or warfare rather than the good side of within-group altruism or sacrifice. That emphasis differs strongly from the one of some proponents of group selection, who seem to consider it the cause for moral goodness.

P.S.: Admittedly, I have myself not distinguished between kin selection and inclusive fitness in the post Darwin on kin/group selection. Other possible conceptions of what is the general and what the special case seem to be in the fray. For example, inclusive fitness and multilevel selection are now often regarded as equally general theories and equally legitimate perspectives on the same problem.

  • Dawkins R (1983) The extended phenotype. Oxford Univ. Press.
  • Hamilton WD (1972) Altruism and related phenomena, mainly in social insects. Ann. Rev. Ecol. Syst. 3:193-232.
  • Hamilton WD (1975) Innate social aptitudes of man: an approach from evolutionary genetics. In: R. Fox (ed) Biosocial Anthropology. John Wiley & Sons, pp. 133-155.
  • Hamilton WD (1996) Narrow roads of gene land, vol. 1. W.H. Freeman, Spektrum.
  • Lewontin RC (1970) The units of selection. Ann. Rev. Ecol. Syst. 1: 1-18.
  • Maynard Smith J (1964) Group selection and kin selection. NAture 201: 1145-47.
  • Segerstrale U (2000) Defenders of the truth. Oxford Univ. Press
  • Sober E, Wilson DS (1998) Unto others. Harvard Univ. Press.