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Herbert Gintis on general equilibrium and inclusive fitness

Books + Ideas, , — October 2014

Oxford draws some great visiting speakers and last week I made it to two lectures by Herbert Gintis, who I knew from his recent book with Sam Bowles, A Cooperative Species. The first talk was a look at General Equilibrium in economics, arguing for an approach with private prices and adaptive expectations and presenting the results from some agent-based modelling. The second was a salvo in the debate about how all-embracing inclusive fitness theory is in explaining evolutionary adaptation. Both lectures probed fundamental theoretical questions, setting them in their historical contexts and going back to basics to help see through what Gintis calls "the smoke and mirrors" of current debate.

The first talk was given to the Economics Society, to an audience mostly of students. General Equilibrium theory goes back to Walras and key results were proved by Arrow and Debreu and others; a key problem is that the equilibria involved are unstable, which has been fudged by having an auctioneer set global prices or by having single representative agents. Gintis' approach is to throw out the fixed preferences and single agent, and to have multiple agents with different preferences (private price vectors) updating themselves by (with some probability) copying successful agents ("adaptive expectations"); it also involves accepting that the system has complex dynamics, which means giving up on analytic results or even numerical solutions and instead simulating it as a Markov process. Results from a (relatively) simple model with firms, workers, taxation, and so forth - some 15,000 variables in all - show that this can generate stochastic stability. (Gintis's papers on this are quite mathematical; "The Stochastic Stability of General Equilibrium" might be the best starting point.)

The second talk was largely a summary of a paper "Inclusive Fitness and the Sociobiology of the Genome" (PDF; Biology and Philosophy, 2014). The background here was the debate engendered by a 2010 paper by Nowak, Tarnita and Wilson and a response by Abbot et al. and there was a certain amount of "bearding the lion in his den" involved, since Oxford, under Dawkins' influence, is a redoubt of traditional population genetics and Alan Griffin was sitting perched in a back corner of the lecture theatre. Gintis pitched his results as a compromise, but actually they're the most fundamental argument against inclusive fitness as all-explanatory that I've seen. He goes back to Hamilton's original paper on inclusive fitness and shows that, however well it can explain adaptation at the level of individual loci, it can't possibly explain the origin of genome-level organisation - of cooperation between genes - because it is indifferent to the "social" or "anti-social" effects of genes. From the paper abstract:

while natural selection explains the appearance of design in the living world, inclusive fitness theory does not explain how. Indeed, Hamilton’s rule is equally compatible with the evolutionary success of prosocial altruistic genes and antisocial predatory genes, whereas only the former, which account for the appearance of design, predominate in successful organisms. Inclusive fitness theory, however, permits a formulation of the central problem of sociobiology in a particularly poignant form: how do interactions among loci induce utterly selfish genes to collaborate, or to predispose their carriers to collaborate, in promoting the fitness of their carriers? Inclusive fitness theory, because it abstracts from synergistic interactions among loci, does not answer this question.

Now the broader conclusion is hardly news to most cell biologists or ecologists, but as a mathematical argument from fundamentals it is more likely to convince population geneticists. (Some of the (economics-derived?) terminology may have been confusing, going by a conversation in the Darwin Cafe afterwards: it may be that genome organisation is parallel to social organisation in this context, but terms like "social" and "predatory" carry a lot of baggage and trying to convince people studying gene regulation networks that they are doing "sociobiology" seems unnecessary.)

Despite evolutionary biology being one of my core interests, this was my first visit to the Tinbergen building (which hosts Zoology and Experimental Psychology). That's at least partly because they really do (for security reasons) restrict entry to students and staff, so I wasn't able to get in during my first two years in Oxford.

I don't know if I'm the only person who went to both lectures, but I fear it's possible.


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