Saturday, July 21, 2012

Group Selection vs. Natural Selection - The On-Going Debate


Here is the brief introduction Wilson offers to this article:
This essay continues a dialogue that started with Steve Pinker's essay titled "The False Allure of Group Selection" published on Edge.org. All readers are invited to comment at the end of this essay. In addition, professional evolutionists are invited to provide more extensive comments on the Social Evolution Forum.

Steven Pinker, along with Richard Dawkins, made some wild and hyper-critical attacks on EO Wilson's newest book, The Social Conquest of Earth. David Sloan Wilson has been a supportive voice for Wilson in the debate, and he is one of the few who are seeking a middle ground between the two models, each of which is true but partial.

Clash of Paradigms


David Sloan Wilson

Author, 'The Neighborhood Project: Using Evolution to Improve My City, One Block at a Time'; Editor-in-Chief, Evolution: This View of Life

Posted: 07/15/2012

Thomas Kuhn (1970) forever changed the conception of science with his notion of paradigms. Before, science was often seen as a relatively straight path to the truth through the repeated formation and testing of hypotheses. What could be simpler?

Kuhn observed that scientists sometimes get stuck viewing a topic a certain way. Their particular configuration of ideas is capable of a limited degree of change through hypothesis formation and testing, but cannot escape from its own assumptions in other respects. This makes the replacement of one paradigm by another a complex and uncertain process.

A clash of paradigms is currently taking place for evolutionary theories of social behavior. In this corner, multilevel selection theory (MLST), a configuration of ideas that began with Darwin and has maintained a degree of continuity, in addition to a degree of change, up to the present. In that corner, inclusive fitness theory (IFT), which can also claim roots in Darwin and has also changed while remaining true to a core set of ideas.

The most recent battle between the two paradigms began when Edward O. Wilson, one of the most celebrated living evolutionists, became a vocal proponent of MLST and started to denounce the utility of IFT. Those who are familiar with Wilson's work know that he has been receptive to MLST all along (read his chapter on group selection in Sociobiology (1975) for details). I should know, because he sponsored the publication of my first article on group selection in the Proceedings of the National Academy of Sciences in 1975 and we have co-authored a number of more recent articles together, including the comprehensive "Rethinking the Theoretical Foundation of Sociobiology" published in the Quarterly Review of Biology in 2007. Wilson's more recent "conversion" was notable less for his acceptance of MLST than his rejection of IFT as a useful paradigm. He was joined by the eminent mathematical biologist Martin Nowak (along with his young-career colleague Corina Tarnita) in a major article in Nature, and elaborated on his views in his most recent book The Social Conquest of Earth.

Proponents of IFT could not take this assault on their paradigm lying down. The responses to the article in Nature included one with 137 co-authors (Abbott et al. 2010). Richard Dawkins wrote a spirited review of Wilson's book in Prospect magazine and Steven Pinker wrote an essay for Edge.org titled "The False Allure of Group Selection". The twenty commentaries (including one by myself) following Pinker's essay provide a fascinating snapshot of the clash between the two paradigms.

Before continuing, I want to stress that the clash between MLST and IFT departs from the Kuhnian notion of paradigms in at least two respects. First, in the major examples discussed by Kuhn, one paradigm eventually collapses and is replaced by the other. Nobody talks about pre-Copernican views of the universe anymore. Even though proponents of MLST and IFT sometimes write as if the other paradigm has or will collapse, there is a strong sense in which a collapse of one paradigm shouldn't be expected. Instead, the two paradigms are like different languages, such as Russian and English, a metaphor that I will elaborate upon below.

Second, Kuhnian paradigms are thought to be incommensurate, such that people who think in terms of one truly cannot see the world in terms of the other. In the case of MLST and IFT, some proponents fit this description but others can easily grasp both paradigms and acknowledge the utility of one, even if they have a preference for the other. I count myself among them as a proponent of MLST who acknowledges the utility of IFT, along with David Queller, a proponent of IFT who acknowledges the utility of MLST. The language metaphor is apt: For people who speak only a single language, another language appears confusing and redundant. People who have become bilingual can easily toggle between two languages and have no wish for one to replace the other.

Queller and I are not alone. There is a sizeable community of evolutionists who are bilingual with respect to MLST and IFT. If anything deserves to collapse in the clash between these two paradigms, it the unilingual position that only one paradigm deserves to exist. When unilinguals become bilingual, the so-called "group selection controversy" will be over.

Diagnosing the claim that one paradigm is confusing and unproductive

The current battle between proponents of MLST and IFT include claims that one's non-preferred theory is confusing, inconsistent, unproductive and adds nothing to one's preferred theory. Here is a sample of quotes from MLST proponents criticizing IFT.

"Yet, considering its position for four decades as the dominant paradigm in the theoretical study of eusociality, the production of inclusive fitness theory must be considered meagre....Inclusive fitness theory is only another method of accounting, one that works for very restrictive scenarios and where it works it makes the same predictions as standard natural selection theory. Hence, there are no predictions that are specific to inclusive fitness theory. (Nowak et al., 2010)."

"Equations seemed to arise out of nowhere in kin selection... Moreover, the concept of "relatedness" seemed to morph and change over time ...Casting a problem in terms of inclusive fitness is like having to undergo elaborate and time-consuming initiations to join an elite club, only to end up with nothing in the way of privileges (Nowak and Highfield 2011)."

"Much of the inadequacy of the theory comes from looseness in the definition of r, hence the very concept of kinship, in various interpretations of the Hamilton inequality....the only unifying theme seemed in time to be that r, originally defined by pedigree, is whatever it takes to make Hamilton's inequality work. The inequality thereby lost meaning as a theoretical concept, and became all but useless as a tool for designing experiments or analyzing comparative data (E.O. Wilson 2012)." Proponents of IFT protested en masse against these statements, but here is what some of them have to say about MLST.

"The first big problem with group selection is that the term itself sows so much confusion. People invoke it to refer to many distinct phenomena, so casual users may literally not know what they are talking about. (Pinker 2012)."

"The first and deepest problem with this debate is that the term group selection does not have any single fixed meaning, but has been used over the last half century to convey a huge and tangled thicket of different and conflicting meanings. The great majority of these are seriously defective as a way of describing reality. (Cosmides 2012)."

"'Group selection', even in the rare cases where it is not actually wrong, is a cumbersome, time-wasting, distracting impediment to what would otherwise be a clear and straightforward understanding of what is going on in natural selection. (Dawkins 2012)."

"Models of group selection are either mathematically equivalent to those based on kin selection but less tractable, or are so nebulous that they can't be analyzed at all. Further, claims that kin selection is less useful than group selection in understanding nature are simply wrong. (Coyne 2012)."

The symmetry of these complaints strongly suggests the existence of two paradigms. Each paradigm is an internally consistent configuration of ideas with explanatory power for those who use the paradigm. But viewing the world from within one paradigm makes the other paradigm appear confusing, unproductive, and so on. The authors of these statements write as if their criticisms are true in some absolute sense, when in fact the criticisms are only true for the authors in a relational sense. That's what the basic phenomenon of paradigms is all about.

Read the rest of this long article.
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