Kin or group selection: which is more confusing

The last decade has seen a bit of a shake out in the domain of kin selection and group selection.

Until recently it was possible to argue that the group selection advocates were consistently more confused about social evolution than users of kin selection. However as group selection advocates learned more about their topic some of them gradually started making sense - and some of them now hold fairly reasonable positions.

Also, it has become clear that some of the opponents of group selection are very confused about the whole topic. Steven Pinker wrote a fairly embarrassing article on the topic in 2012 - and some of that article's commentators made similarly embarrassing follow-ups.

Popular blogger Jerry Coyne has written a string of articles about group selection. He doesn't seem to have made much effort to understand what advocates of group selection are saying - and so produces mostly straw man attacks.

Richard Dawkins isn't exactly helping either. For example, he writes:

Is a group a replicator? No. We do not have a 'group pool', a metapopulation in which some groups are more successful than others at making replicas of themselves, replicas that persist through geological time.

This seems like classic replicator rot to me. Try talking about copying and heredity instead, and we do indeed have collections of groups, some of which are better at making copies of themselves than others. Maybe none of them are especially brilliant at making copies of themselves: but so what?

The broad equivalence between kin and group selection makes the issue of which framework causes more confusion into a significant issue. One of the main problems with group selection historically has not been that it's wrong, but that it is confusing and easy to mis-apply.

The confusion by the group selection opponents is unfortunate. It doesn't help to make the case that kin selection is less confusing and less subject to abuse.

However, I think it is still dwarfed by the confusion related to group selection. Martin Nowak and E.O. Wilson are perhaps the most prominent examples - but it seems to me that they represent only the tip of a pretty substantial iceberg.

Kin selection and its critics

Here's an interesting new paper: Kin Selection and Its Critics - Jonathan Birch and Samir Okasha.

Samir Okasha wrote a rather flawed book on group selection some years ago. However, this article shows that he is doing a good job of keeping up with developments in the field - and it isn't so easy to find significant mistakes in this large recent article.

I think one problem is that it takes the work of Nowak and Wilson a bit too seriously.

In one place the authors argue against equivalence, saying:

In one respect, the kin selection approach is arguably more general than the multilevel approach, because the latter requires that individuals be nested into nonoverlapping groups, as in figure 4; this is necessary for the decomposition technique in box 2 to apply (Hamilton 1975, Okasha 2006, Frank 2013). Groups of this sort exist in some taxa (e.g., the colonies of many social insect species). But in other cases, individuals engage in social interactions with their conspecifics, but there are no well-defined, discrete groups. The kin selection approach can handle such cases easily; indicative of this is that in deriving equation 4 above (box 1), we did not make use of the fact that the individuals were nested into nonoverlapping groups. Therfore, the claim that kin and multilevel selection are formally equivalent requires at least this qualification.

This doesn't seem like too much of a stumbling block to me. The modern "group selection" approaches depend critically on defining a "group" to include any collection of organisms - no matter how fleeting or ephemeral. You have to buy into this conception of a "group" for the approach to be worth considering in the first place.

The authors say:

The widespread preference for kin selection may be partly due to multilevel selection's association with the flawed good-of-the-group tradition of the 1950s and 1960s and the associated superorganism concept, of which many biologists remain suspicious. It is undeniable that the careless appeal to group-level advantage as a way of explaining a trait's evolution led to serious errors in the past, so biologists’ wariness of this mode of explanation is understandable.

That's about the size of it. However, this paints group selection's problems as being in the past. I think that this is inaccurate. A fairly cursory look at the evolutionary social sciences shows that misapplication of group selection is still widespread.

The essay closes with a plea for "causal aptness": use kin selection when you have relatives, use group selection when you have interacting groups. This proposal sounds reasonable - but I think it would do little to stem the existing misuse of group selection. The problem is that people see differential group reproduction, reach for group selection, and produce just-so stories about how group traits are the product of differential group extinction or reproduction. This is a systematically bad methodology that use of group selection directly encourages. Using "causal aptness" would probably boost usage of group selection. That seems as though it is likely to cause a range of negative outcomes associated with the misuse of group selection - and so I regard the proposal as suspect.

"Causal aptness" is one proposal. A big health warning relating to the misuses of group selection is another. I think that, if you adopt the first proposal, you should also adopt the second one.

Disagree with Steve Frank

I read Steve Frank's paper A new theory of cooperation recently. Steve Frank is an expert, but I thought that this paper was mostly wrong. The theme of the paper is that suppression of competition within groups represents a new theory of cooperation - that beyond kin selection and reciprocity. He credits the development of the idea to Richard Alexander - in The Biology of Moral Systems.

Many of the examples of suppression of competition within groups Steve gives are due to kin selection. Steve disagrees with this, writing:

[...] the main weakness of the theory was also apparent. Extensive cooperation occurs between nonrelatives. Different genes in genomes are functionally integrated but not related. Larger human societies often have many highly cooperative but distantly related individuals. Some of this cooperation between nonkin can be explained by extensions of reciprocity to a general notion of mutual benefit for interacting partners (West Eberhard 1975).

In the early 1980s, kin selection plus these extended notions of reciprocity were the main conceptual tools. Those limited conceptual tools led to blind spots about unsolved problems. Only rather forced theories of mutualism could work for the nearly complete integration of genes into cooperative genomes. Only a very enthusiastic belief in the scope of reciprocity could explain the broad social integration in larger groups of weakly related human

However, cooperation between groups of "unrelated humans" that is not due to reciprocity has turned out to be largely associated with cultural kin selection. This is kin selection applied to memes - not genes. Many of Steve Frank's examples fit onto the familiar kin selection / group selection axis - though he apparently doesn't fully realise this.

There is indeed another force that produces cooperation besides reciprocity and kin selection - and that is "manipulation". Manipulation is where agents impose their wills on other agents. Teams sometimes cooperate because they are cooerced into doing so by supervisor figures. Manipulation helps to explain suppression of competition in cooperative genomes. The efforts of individual genes to bypass meiosis is thwarted by the "parliament of genes" in the genome. Manipulation isn't the same as kin selection or reciprocity - so Steve Frank's paper is partly correct.

However, I think that there's a good reason to call this "manipulation" and not "suppression of competition". "Suppression of competition" is just another way of saying "cooperation". Explaining cooperation in terms of "suppression of competition" seems pretty circular to me.

Manipulation is responsible for the symbiont hypothesis of eusociality. This was proposed in 1934. The "parliament of genes" phrase comes from Leigh (1971). Since manipulation is such an obvious and well-known phenomenon, there may well be earlier examples of it being involved to explain cooperative behaviour. As a theory of cooperation, the idea is not exactly new - and I'm pretty sure that Richard Alexander wasn't responsible for it.

In The Biology of Moral Systems, Richard Alexander wrote:

It is a common error to suppose that something additional to nepotism and reciprocity is required to account for the structure of society. (p.153)

Here it sounds as though he repudiates this particular revolution.

West and Gardner on kin vs group selection

West and Gardner have not been shy about pointing out the virtues of kin selection over group selection. Here they are with a summary in 2013:

The most frequently used methods are neighbour-modulated and inclusive fitness. In particular, modern neighbour-modulated fitness methods allow the modeller to go from the underlying biology to an expression or fitness, in a way that facilitates the development of relatively general models [8,27,28,35,37]. In contrast, the group selection approach is used relatively little for modelling specific traits partly because as soon as one moves away from the simplest, most abstract models, and wants to add in real world biology, it often becomes analytically intractable — for example, when populations are structured into different classes of individual, according to sex, age, caste or ploidy [38–40].

I know these folk also have plenty of other objections to group selection. Here, forced to pick one, they went for analytic tractablility. It seems like an odd choice to me. As a veteran computer modeller, analytic tractablility comes relatively low on my list of virtues. I would probably list group selection's association with junk science as my number one complaint.

Identity by descent: a confusing concept

There's a lot of discussion of kin selection using the term "identical by descent" and "identical by state". The idea of "identical by descent" is that genes are shared as a result of direct descent from a common ancestor - without recombination or mutation. "Identical by state" just means that the DNA sequence is shared. It is said that 50% of their genes with their daughters "IBD".

I think the "identical by descent" terminology is confusing and not useful. In biology, if genes are identical, they are practically always identical through being copied from one (or more) shared ancestors. Mothers share more than 50% of their genes with their daughters - due to genes that have reached fixation, inbreeding and so on. However they still share these gene sequences due to descent from shared ancestors. As to a gene mutating into another form and then mutating back again. If you do the sums, for a gene of any reasonable size this rapidly becomes ridiculously unlikely. There's too much scope for neutral mutations elsewhere. In practice, when genes are identical, the odds are enormously in favour of this being due to shared ancestry. The idea that recombination with an identical gene makes genes not "identical by descent" is an awful one. They are still "identical by descent" - just descent from various different ancestors.

You can't say that mothers share 50% of their genes with their daughters "IBD". It is confusing and mistaken. If you want to use the 50% figure, you have to find another reason for doing so.

Analysis of "group selection and inclusive fitness are not equivalent"

I briefly analyzed the paper:

Group selection and inclusive fitness are not equivalent; the Price equation vs. models and statistics by Matthijs van Veelen, Julian Garcia, Maurice W. Sabelis, Martijn Egas.

This is one of the papers mentioned on my equivalence naysayers page.

The paper claims that group selection and kin selection are not equivalent. It argues that inclusive fitness requires fitnesses to be "additive". Additive fitness is a common assumption when deriving Hamilton's rule - and is indeed associated with inclusive fitness. However, inclusive fitness is a simplified model of kin selection. Kin selection enthusiasts are not too impressed with such critiques - the limitations of inclusive fitness are well known. The paper uses "kin selection" and "inclusive fitness" as though these concepts are interchangeable. I think this is not all that useful an approach.

Kin selection doesn't depend on fitness being additive. That idea is associated with inclusive fitness and Hamilton's rule. These are concepts associated with simplified models of kin selection.

Hamilton advocated using "inclusive fitness" instead of "kin selection". Hamilton (1975) "Innate social aptitudes of man" says:

The usefulness of the ‘inclusive fitness’ approach to social behaviour (i.e. an approach using criteria like (b K-k) > 0) is more general than the ‘group selection’, ‘kin selection’, or ‘reciprocal altruism’ approaches.

However, I think the pendulum has swung away from "inclusive fitness" and back towards "kin selection" as the term of choice. That's what Gardner and West use tend to use, for example. I'm with them.

Steven Frank on why kin selection beats group selection

Here's Steven Frank writing fairly recently - on why kin selection is better than group selection:

In more complicated biological problems, it often becomes difficult to express all of the selective forces in terms of relative variances among groups. The problem is that patterns of interaction may differ with respect to different processes, such as mating, competition between certain individuals such as males, and competition between other individuals such as females. In that sort of realistic scenario, it is far easier to trace pathways of causation through a series of partial correlations that can be interpreted as an extended form of kin selection analysis (Frank, 1986, 1998). In practice, it is rarely sensible to express such multiple pathways of causation by expressions of relative amounts of variance among groups, although such expressions may be possible mathematically. For that reason, kin selection often becomes a more natural form of analysis for realistic biological problems, leading to a generalized path analysis framework.

I think this is part of it. The idea of a "trait group" represents an attempt to overcome this issue. However there are other reasons too:

• Kin selection is more quantification-friendly - with its r, b and c;
• In practice, use of group selection often seems to lead to naive group selection;
• Group selection avoids problems where kin selection is obviously responsible;

These problems have also led to issues associated with scientific status. Group selection is promoted by scientific rebels who try and pick holes in established views. That appeals to some - while repulsing others.