Saturday, 28 December 2013

Why can't we all just get along?

After the 2010 Nowak, Tarnita, & Wilson affair, Samir Okasha weighed in with a comment in Nature, effectively asking: why can't we all just get along?

The paper was titled: Altruism researchers must cooperate. It is indeed ironic that the science of cooperation has led to so much scientific acrimony.

In the paper, Samir embraces equivalence, writing:

kin and multi-level selection are not alternative theories; they simply offer different takes on the question of how social behaviour evolved. Proponents of kin selection, for example, explain sterile workers in insect colonies by saying that the workers are helping the queen to reproduce, and thus boosting their own inclusive fitness. Proponents of multi-level selection argue that the workers are providing a benefit to the colony as a whole, thus making the colony fitter than other colonies. These explanations may seem different, but mathematical models show that they are in fact equivalent
He says the persistent rival camps are a puzzle since:

The existence of equivalent formulations of a theory, or of alternative modelling approaches, does not usually lead to rival camps in science. The Lagrangian and Hamiltonian formulations of classical mechanics, for example, or the wave and matrix formulations of quantum mechanics, tend to be useful for tackling different problems, and physicists switch freely between them.
His explanation:

History shows that, despite its enormous empirical success, evolutionary biology is peculiarly susceptible to controversy and infighting. This is particularly true of social evolution theory, in part because of its potential applications to human behaviour.

I think this is essentially correct. People fight over application of evolutionary theory to humans for many reasons, but among them are: "it's complicated", and "it's important to get it right".

Group selection doesn't score well in the latter category. It isn't so much that it is wrong, it's more that it has led to decades of muddle, confusion and poor-quality science. If kin selection and group selection are feeling different parts of the same elephant, kin selection has hold of the trunk, while group selection is groping the left thigh.

It is certainly frustrating to have all the biology papers using kin selection, while all the humanities papers seem to use group selection.

A big part of the problem is misunderstandings surrounding cultural evolution. Cultural evolution has historically lagged by decades behind conventional evolutionary theory. There was a revolution in the 1970s in which group selection fell out of fashion, and kin selection became much more popular. A parsimonious explanation of the penchant for group selection in the social sciences is that the field of cultural evolution has yet to go through this transition. The significance of relatedness between memes and memeplexes has yet to be fully appreciated.

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.



Sunday, 8 December 2013

Kin selection is very general

Kin selection theory can only be applied when organisms are influenced by their kin. However this happens at least once in every organisms' lifetime - when they are born.

Kin selection applies to calculations of parental investment and cases where there is parent-offspring conflict. Since all multicellular creatures have a parent-offspring asymmetry and provide some kind of resource bolus to their offspring, that means that kin selection applies to all multicellular organisms.

In other organisms, kin selection is also often relevant. Many microscopic organisms exhibit limited dispersal - and so are surrounded by their kin. If your kin are nearby, you should typically curb your pollution, share your food, and commit suicide if you are compromised by pathogens. Many parasites spend much of their time inside their hosts - where they are often surrounded by their kin.

Kin selection also applies to cultural variation - in the form of cultural kin selection - where it is similarly ubiquitous.