Sunday, 4 January 2015

Herbert Gintis vs inclusive fitness theory

Herbert Gintis has an elaborate attack on inclusive fitness theory on his web site. It's titled: Inclusive Fitness and the Sociobiology of the Genome. It says, among other things:

The general point is that if there is a conflict among loci concerning fitness maximization, and if the frequency of alleles at one locus affect the fitness costs and payoffs at other loci, then it is logically impossible that the allele at each locus maximize its inclusive fitness. Rather, the proper setting is evolutionary game theory [...]

I think this is a case of expecting too much from the concept of maximization. The idea of maximization does not imply that all parties reach the maximum they are seeking. It doesn't even imply that they increase the value they are trying to maximize. A hill-climber might be climbing a hill on a mountain that is sinking into the sea. Their elevation may decrease until it reaches zero and they die. This is quite consistent with the idea of maximization.

Gintis apparently claims that frequency-dependence invalidates the idea of maximization of inclusive fitness:

If the genome’s success is based on a pattern of cooperation, promotion, and suppression across loci, which will occur, for instance, if the production of a protein, RNA sequence, or social behavior requires the collaborative activity of many genes (Noble 2011), or if there are frequency dependent social interactions among individuals in a social species (Maynard Smith 1982), then neither genes nor individuals can be characterized as maximizing inclusive fitness. The conditions under which a population genetics model of gene flow implies fitness maximization at the gene or individual level has been carefully explored (Grafen 1999, 2002, 2006; Metz et al. 2008; Gardner and Wild 2011; Gardner West and Wild 2011). With frequency independence, they affirm the maximization hypothesis. With frequency dependence, the hypothesis it is in general false, and no careful researcher has ever claimed otherwise.

Frequency dependence typically means that genes are spending time in environments that differ from the average of the environments they evolved in. It's a case of adaptive lag - where organisms are adapted not to their current environment, but to a weighted average of ancestral environments. This is a classic case where organisms sometimes behave sub-optimally in ways that don't further their own interests.

In such cases, organisms don't always act to maximize their inclusive fitness - but rather act to maximize their inclusive fitness under the hypothesis that they are in an environment that is like the one that their ancestors evolved in. Of course, that hypothesis might be mistaken.

In fact, sufficiently sophisticated creatures might be able to evolve a superior strategy - where they sample the frequency involved and change their behaviour adaptively, based on the observed frequency. So, what frequency dependence often boils down to is that organisms can sometimes fail to maximise their inclusive fitness - because they have cognitive limitations and make mistakes.

In this case, I feel that Gintis is expecting too much from inclusive fitness theory. It doesn't claim that all creatures maximize inclusive fitness perfectly. Creatures have all kinds of imperfections and limitations that prevent them from acting as perfect maximizers.

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