Wednesday, 20 June 2012

Group selection and kin selection are formally equivalent

Update 2013-12-30: there's now a more up-to-date version of this article here.

No memes today - but I should probably comment on the ongoing "group selection" spat:

Richard Dawkins, E. O. Wilson, Martin Nowak and Steven Pinker have all weighed in on group selection recently. They are all wrong about it.

Richard Dawkins is focussed on the "old" group selection - the object of criticism by J. Maynard Smith, G. C. Williams - and himself. In the endnotes to the second edition of The Selfish Gene (1989) he wrote:

Kin selection is emphatically not a special case of group selection.
His views do not appear to have changed. In his 2012 review of Wilson's "The Social Conquest of Earth" he states:

[Edward Wilson] treated kin selection as a special case of group selection, an error which I was later to highlight in my paper on “Twelve Misunderstandings of Kin Selection” as Misunderstanding Number Two. Kin may or may not cling together in a group. Kin selection works whether they do or not.
Here Dawkins is apparently talking about the "old" group selection. Wilson, Wilson (and practically everyone else) has moved on - and few use the term "group selection" in that sense any more. The "new" group selection models are really the only ones remaining on the table.

Martin Nowak, Corina Tarnita and Edward O. Wilson (2010) have this to say on the topic:

Group selection models, if correctly formulated, can be useful approaches to studying evolution. Moreover, the claim that group selection is kin selection is certainly wrong.
E. O. Wilson and Martin Nowak are in spectacular muddle on the topic - as practically everyone else agrees.

E. O. Wilson is still going strong regarding his kin selection denial as of June 2012.

Steven Pinker also doesn't understand the topic. He describes the new group selection by saying:

sometimes the term is used as a way of redescribing the conventional gene-level theory of natural selection in different words: subsets of genetically related or reciprocally cooperating individuals are dubbed "groups," and changes in the frequencies of their genes over time is dubbed "group selection."
He then says: "To use the term in these senses is positively confusing". Expert David Queller sets Pinker straight in the comments right under Pinker's article.

These days, there's a scientific consensus about group selection - and these folk are not part of it.

As Marek Kohn said in 2008:

There is widespread agreement that group selection and kin selection — the post-1960s orthodoxy that identifies shared interests with shared genes — are formally equivalent.
The observation dates back to Hamilton (1975). Queller (1992) is another important paper on the topic.

Modern paper titles in the area include: "Group selection and kin selection: two concepts but one process" and "Group selection and kin selection: formally equivalent approaches".

In "Social semantics: how useful has group selection been?", West, Griffin and Gardner (2009) state:

There is no theoretical or empirical example of group selection that cannot be explained with kin selection.
The theoretical equivalence of kin selection models with those of the new group selection seems to be fairly widely recognized. Wilson and Wilson (2007) seem to agree, saying:

The theories that were originally regarded as alternatives, such that one might be right and another wrong, are now seen as equivalent in the sense that they all correctly predict what evolves in the total population. They differ, however, in how they partition selection into component vectors along the way. The frameworks are largely intertranslatable and broadly overlap in the kinds of traits and population structures that they consider.
The term "group selection" has been radically redefined since the criticisms of Dawkins, Williams and Maynard Smith.

Formal models of "group selection" and "kin selection" are now widely regarded as producing the same results. Gardner and Grafen (2008) say:

group selection has already been incorporated into social evolution theory, and is found to be exactly equivalent to kin selection: the two approaches are simply different ways of describing the same evolutionary process and both lead to the prediction that individuals should maximize their inclusive fitness
Kerr and Godfrey-Smith (2002) recommend switching between the two perspectives - saying:

we also argue that each type of model can have heuristic advantages over the other. Indeed, it can be positively useful to engage in a kind of back-and-forth switching between two different perspectives on the evolutionary role of groups. So the position we defend is a “gestalt-switching pluralism.”
To his credit, group selection enthusiast David Sloane Wilson is now on the correct side in this debate. So is group selection enthusiast Peter Richerson.

Even group selection hater Jerry Coyne is at least aware of the consensus on the topic. His articles on the topic are unbalanced, though. Kin selection has its advantages, so does group selection. However, Jerry seems unaware of that. Biologists can't simply bury all the group selection nonsense by declaring group selection to be redundant - it isn't a redundant idea.

Daniel Dennett has a mild-mannered response to Pinker's article, but it looks as though he doesn't understand the topic very well either.

Wikipedia also seems rather confused about the topic, saying:

"Kin group selection" should not be confused with the concept of "group selection": a theory that a genetic trait can become prevalent within a group because it benefits the group as a whole, regardless of any benefit to individual organisms.
Dawkins, Wilson, Nowak and Pinker certainly didn't get the memo on this one.



  1. I think that you rcriticisms do not hold. Interestingly Dawkins cites Grafen as the ultimate source of understanding of the differences between group and kin selection. The problem is that the redefinition you allude to might make people think that the old arguments against group selection also invallidate kin selection. So being precise about what's being said is not a defect. I would sitck to the old divide in order to make things clear.

  2. Indeed you miscite and misquote Coyne. He says that group selection works only when it is a form of kin selection and that the other cases -arguably reasonable forms of group selection- do not work if they are not kin selction. THus the relationship between the two is not one of "if and only if". Failure to understand this produces a lot of confussion and irrationality that pervades all your post.

  3. Actually I didn't quote Coyne at all. I agree with: "Group selection and kin selection: Two concepts but one process" (2007).

    The "old" concept of group selection was never very much use in the first place. It was created almost entirely by critics.

  4. Yes, there are dud forms of group selection. There are dud forms of kin selection too - for instance, versions that fail to take any account of cultural relatedness. However, scientific theories are better judged by their strongest variations than by their weakest ones.

  5. "The term "group selection" has been radically redefined since the criticisms of Dawkins, Williams and Maynard Smith". The logical next step, as it seems to me, is to EXPLAIN the new models, definitions etc. I am curious which target group you had in the back of your mind when writing this.

  6. The group selection advocates have explained their models elsewhere. E.g see "trait group selection". Explaining how these models work is beyond the scope of this post.