Sunday, 15 December 2013

Nowak and Wilson are at it again!

You might think Nowak and Wilson would have had their fingers burned in the reaction to their 2010 Nature paper.

However, it seems as though they are at it again. They have a PNAS paper titled: Limitations of inclusive fitness by Benjamin Allen, Martin A. Nowak, Edward O. Wilson.

They deny that evolution can be usefully viewed as an optimization process, saying:

Thus, evolution does not, in general, lead to the maximization of inclusive fitness or any other quantity.

That's complete nonsense: Allen, Nowak, and Wilson don't know what they are talking about. Optimization models are perfectly general - and can model any dynamical system.

The guts of their paper is a criticism of the application of Price's equation to inclusive fitness.

Their main beef is linearity. They are concerned that the 'adding' and 'subtracting' that goes on in the definition of inclusive fitness limits its generality. They write:

Inclusive fitness assumes that personal fitness is the sum of additive components caused by individual actions. This assumption does not hold for the majority of evolutionary processes or scenarios.
However, this linearity doesn't really cause problems - since you can approximate non-linear curves using a series of line segments.

Inclusive fitness is mostly concerned with the issue of whether some helping behaviour will evolve. It calculates whether the net selective effect of a behaviour on the frequency of a gene responsible for it (some of which may be copies in relatives of the actor) is positive or negative (relative to a set of alternatives) in the current environment. The math of inclusive fitness tells you whether the gene is selectively favoured. That's not quite the same thing as whether the behaviour will evolve (maybe it will drift into extinction) - but it's a good start. Nobody ever thought that the behaviours and genes involved had to not interact. Nobody thought that the rate of change of the frequency of the gene would be fixed over time. Maybe the environment will change in crazy non-linear ways in the future - and you'll have to redo your sums.

Basically, it isn't true that inclusive fitness theories assume that personal fitness is a linear sum of action fitness deltas. An action can change the environment (or the actor) in ways that affect the costs and benefits of future actions - and this is perfectly compatible with Hamilton's rule. It means that you may have to apply the rule more than once, is all.

Allen, Nowak, and Wilson's paper is like saying: I've got this crazy non-linear function, there's no way your linear approximation can match it. Except that: yes, there is - a series of linear functions can approximate any other function arbitrarily closely.

If you think that making this sort of objection is childish, I think that you're right - it is childish.

The paper says it was: "supported by a grant from the John Templeton Foundation". It seems like even more fuel for those who think that the Templeton Foundation is systematically distorting science.



1 comment:

  1. I would be careful with your criticism on this. You are absolutely right that Nowak and Wilson are a bit polemic, but recognize that they are also correct that there have been, and never will be, a study that measures the strength of kin selection. In the agricultural world, where nobody cares about optima and they very much care about selection intensities they use multilevel selection and have absolutely no use for kin selection. In short to say that kin selection is the only approach is demonstrably wrong. I think a very good case can be made for the idea that it is also emphatically not the best approach.