Clash of Paradigms: Why Proponents of Multilevel Selection Theory and Inclusive Fitness Theory Sometimes (But Not Always) Misunderstand Each Other

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 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 solar system 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.

Why the two paradigms are incommensurate

For readers who are unfamiliar with MLST and IFT, here is a brief description of why they are so incommensurate with each other. To begin, they define basic terms such as “individual selection” and “altruism” in different ways. For MLST, individual selection is defined in terms of relative fitness within groups. A trait is altruistic when it benefits others or the group as a whole and decreases the fitness of the altruist, relative to other members of its own group. For IFT, direct individual fitness is defined in absolute terms. A trait is altruistic when it benefits others or the group as a whole and decreases the absolute fitness of the altruist. The term “group selection”, which plays a key role in MLST, does not exist within IFT. The term “inclusive fitness”, which plays a key role in IFT, does not exist within MLST.

The differences between the two theories are sufficiently great that W.D. Hamilton regarded MLST as a failed theory and developed IFT to explain the evolution of altruism without invoking group selection. Briefly, his method involved calculating the effect of an altruistic act on the absolute number of copies of the altruistic gene that are identical by descent. The same altruistic act benefits copies of the non-altruistic gene and copies of the altruistic gene that are not identical by descent, but these effects can be ignored because they do not alter the frequency of the altruistic gene in the gene pool. Only effects on genes that are identical by descent produce evolutionary change. Given the assumptions of the model, Hamilton’s rule gives the conditions for the spread of the altruistic gene in the gene pool.

Given the same assumptions, it is possible to calculate the relative fitness of the altruistic gene within and among groups. Consider a group of relatives that are socially interacting with each other. Some are altruistic and others are not. We don’t keep track of genes that are identical by descent. Instead, we calculate the effect of the altruistic act on the frequency of the altruistic gene within the group of relatives. The altruistic gene is at a selective disadvantage within the group. The only way for the altruistic gene to evolve in the total gene pool is if groups with more altruists contribute more to the gene pool than groups with fewer altruists.

Both methods employ the same assumptions and make the same predictions about when the altruistic gene evolves in the total population, but they seem so different that even their developers were confused about their equivalence. The history of their confusion is well known to scholars but deserves to be more widely known among the general public. The first MLST model of altruism in family groups was by George and Doris Williams and was published in the journal Evolution in 1957. Hamilton published his IFT model in 1963 in The American Naturalist and 1964 in the Journal of Theoretical Biology. All of these are top journals and it is silly to claim that either formulation is confusing in some absolute sense. Hamilton was unaware of the Williams & Williams paper in the development of his own theory. George Price developed a MLST model that partitioned natural selection into within- and between-group components, which was first published in the journal Nature in 1970. It was more general and elegant than the Williams & Williams model and could be applied to family groups in addition to many other kinds of groups. Only when Hamilton encountered the Price equation did he fully appreciate the equivalence between IFT and MLST, as he described in a paper published in 1975. This history is recounted for a general audience by the historian of science Oren Harman in his book The Price of Altruism (2010), and recently summarized by Eric Michael Johnson (2012), who blogs for Scientific American, in the context of the current clash.

1975 was also the year that I published my first article on group selection in the Proceedings of the National Academy of Sciences, with E.O. Wilson as the sponsoring editor. One of my contributions was to define the concept of a trait-group. Groups do not exist in any absolute sense; instead, they are typically defined in reference to particular activities or traits. This is true in everyday language (e.g., my nation, my school, my church, my bowling club) and it is also true for evolutionary models of social behavior. A model for the evolution of warning calls will define the group as the set of individuals within earshot of each other. A model for the evolution of resource conservation will define groups as the set of individuals who compete for the same resource. Mathematically, whenever the fitness of an individual is influenced by other individuals, it must be defined by a function f(N,p), where N and p reflect the number and genetic composition of the group influencing the focal individual’s fitness. All models of social behavior must define the grouping that is appropriate for a particular trait, which is the trait-group for that model.

My second contribution was to show that when trait-groups are examined from a multilevel perspective, the core claim of group selection is often correct. In other words, traits can evolve in the total population even when they are selectively disadvantageous within groups. This result was in contrast to the prevailing belief that higher-level selection is almost invariably weak compared to lower-level selection. Fancy math was not required to draw this conclusion. A simple algebraic model was sufficient. My model was less general than the Price equation, but both models made the same point.

Ed Wilson was cautious about publishing my paper in PNAS. After all, acceptance of group selection was at its low ebb and he would appear foolish if there was something wrong with my argument. He therefore had it thoroughly reviewed by theoretical biologists, who examined my argument from stem to stern before deciding that it was correct. That was 37 years ago, and still the clash between the two paradigms continues. To give a sense of proportion, 37 years represents 24% of the history of Darwinian thought, starting with the publication of Origin of Species. If that’s not an example of incommensurability, what would be?

How Equivalence Changes the Concept of Paradigms

MLST and IFT provide outstanding examples of paradigms in terms of their incommensurability, but now it is important to clarify why they depart from the concept of paradigms in other respects.  In the examples that Kuhn described, such as the Copernican revolution, one paradigm (the view that the earth is the center of the solar system) is eventually replaced by the other (the view that the sun is the center of the solar system). There was a right and wrong about the matter, even though the rejection of the false paradigm was not smooth.

In the case of MLST and IFT, neither paradigm is wrong in the way that the pre-Copernican view of the solar system was wrong. Instead, they parse the conceptual space in different ways but reach the same conclusion on right-and-wrong issues such as when a given altruistic behavior evolves in the gene pool. Different metaphors are employed to describe their equivalence, such as “accounting methods”, “languages”, or “perspectives”.

All three of these metaphors are apt in their own ways. Imagine creating a spreadsheet to organize your finances. In some ways it is useful to organize your expenditures in terms of date. In other ways it is useful to organize them in terms of categories such as food, business, and so on. Both are equally correct and deserve to coexist because they are useful for different purposes. In the same way, MLST accounts for gene frequency change in the total population by creating the categories “within-group selection” and “between-group selection”.  The IFT method creates the categories “genes identical by descent” vs. “genes that represent a random draw from the gene pool”. Neither is wrong and they deserve to coexist if they are useful for different purposes.

Different languages are not equivalent at the level of single words; if they were, then translating between languages would be easy. Instead, different languages parse the world in different ways. The concept represented by a single word in one language can require a treatise to understand in a different language.  If the entire world spoke a single language, then a precious form of diversity would be lost. Nevertheless, it is possible to translate among languages and gifted translators are admired almost as much as the authors that they translate.  If MLST and IFT are like different languages, then each can offer unique insights by parsing the evolutionary process in different ways, even though the insights from one can be translated into the other language.

Finally, imagine that you are planning to ascend a mountain with a friend. As you survey its contours, certain features are difficult to make out from where you are standing. It makes sense for your friend to stand in a different spot so that you can collectively get a better view of the mountain’s contours.  MLST and IFT might offer different perspectives on the same evolutionary process, in the same way that you and your friend offer different perspectives on the same mountain.

All of these metaphors help to explain how two scientific paradigms such as MLST and IFT can be different yet worthy of coexistence, a combination that goes beyond the traditional concept of paradigms. Against this background, it is interesting to revisit some of the arguments quoted above, which are intended by proponents of one paradigm to drive the other paradigm extinct.

Consider the argument that a given paradigm is confusing.  I am confused by Russian, but that’s my problem, not a problem with the Russian language. My confusion will cease as soon as I learn Russian. When we view paradigms as like languages, the “confusion” criticism becomes no criticism at all.

Or consider the argument that every result derived from one paradigm can also be derived from the other paradigm. This is expected for different accounting systems, languages, and perspectives, but it ignores the advantages inherent in their differences.  If I need to tally my business expenses, an accounting system organized by date will be cumbersome, even though it might be possible. A given result that emerges easily from one perspective might be opaque from another perspective and only derivable in retrospect. The inter-translatability criticism becomes no criticism at all.

Finally, consider the argument that a given paradigm changes over time. Both paradigms have changed profoundly over the decades. For IFT, the interpretation of r became generalized beyond genealogical relatedness. For MLST the interpretation of groups became generalized. These changes are regarded as progress within each paradigm and are only confusing to those who don’t speak the language.  The “always changing” criticism becomes no criticism at all.

In short, the current clash between proponents of MLST and IFT is primarily a clash between people who are fluent in one paradigm and confused by the other paradigm, which they falsely attribute to the other paradigm in some absolute sense. This is like saying “Russian is confusing”, rather than “Russian is confusing for a non-Russian speaker such as myself.” They also expect that their paradigm will triumph over the other paradigm, in the same way that the Copernican view triumphed over the pre-Copernican view. Replacement is not expected for accounting systems, languages, or perspectives, and it shouldn’t be expected for MLST and IFT.

Listen to the Bilinguals

The metaphors of paradigms as like accounting systems, languages, and perspectives are apt in another respect. They all imply that a single person can master more than one paradigm. It is possible to organize your financial records by date and by category. It is possible to be bilingual. And a single climber can view a mountain from different locations. These stand in contrast to the standard view of paradigms, which implies that incommensurability is inescapable.

Many evolutionists are fluent in both MLST and IFT, a fact that is sometimes obscured by the chest-thumping rhetoric of unilinguals. Here is a sample of comments by bilinguals who responded to Steven Pinker’s essay:

Modern group selection theory is as mathematically rigorous as individual selection or inclusive fitness theory.  I say this despite being someone who favors the inclusive fitness approach and whose entire career has been based on it.   I think of these less as alternative theories that make different predictions than as two different languages describing the same world.  They simply divide up fitness in slightly different ways – inclusive fitness into effects on self versus others, and multilevel selection into between-group and within-group parts – and a simple partition of fitness should not alter predictions (Queller 2012).

As with other kinds of dynamic processes, models of genetic evolution can be built many different ways. The issue of “group selection” revolves around the choice of an accounting system: how does one wish to track fitness or changes in gene frequencies. In many cases (though not all), the exact same process can be represented and developed using quite different evolutionary accounting systems [1-3]. These accounting systems include (1) individual fitness, (2) inclusive fitness, and (3) multi-level or “group” selection (Henrich 2012).

The first misconception here is the view that group selection is incompatible with kin selection. It is not. Kin selection says that the fitness of an individual depends on the genes of his kin and not just his own genes. Group selection says the fitness of an individual depends on the characteristics of the group he is in, not just his own genes (Gintis 2012).

For these and many other evolutionists, toggling back and forth between MLST and IFT has become normal science, with no need for chest-thumping rhetoric. The choice of theory is simply a matter of choosing the best tool for the job.

The coexistence of paradigms does not mean that everyone is entitled to their own opinion on important empirical claims. As with the standard view of science, many hypotheses are just plain wrong and both paradigms must come to an agreement in rejecting them. Consider the central claim of MLST, which is that prosocial traits can evolve even when they are selectively disadvantageous within groups. The only way to evaluate this claim is by comparing gene frequency change within groups to gene frequency change in the total population. MLST is designed to make this comparison, like an accounting system designed for a certain purpose. IFT is not designed to make this comparison. Even though it includes the same information, it is like an accounting system organized by a different set of categories than those called for. Work is required to re-organize the information, but when this is done, IFT must come to the same conclusion as MLST, or else one of them is wrong.

In the current battle among unilinguals, this kind of empirical inquiry is a civilian casualty. To pick E.O. Wilson’s Social Conquest of Earth as an example, he makes a number of important empirical claims about the evolution of eusociality, in general and in relation to our own species, which he frames in terms of MLST. Bilinguals know that the same claims can be examined from an IFT perspective and that the two paradigms must ultimately come to the same conclusions.  Yet, this inquiry has been largely halted by the chest-thumping rhetoric over which paradigm is the right one.

Beyond Group Selection

This essay is about two paradigms but it also stretches the concept of paradigms to include some that deserve to coexist rather than replacing each other. The metaphors of paradigms as accounting systems, languages, and perspectives are relevant to other topics in science, in addition to the group selection. In fact, Pinker’s essay is notable for addressing another topic—cultural evolution—in ways that have nothing to do with group selection. Once again, he defends a certain configuration of ideas as the only right one and disparages other configurations as confusing, unproductive, and changing. The possibility that he might be like a non-Russian speaker who blames the language for being confusing doesn’t occur to him. All scientists and intellectuals, indeed all people, need to become multi-lingual to avoid this kind of error.


Abbott, P., Abe, J., Alcock, J., & al., et. (2010). Inclusive fitness theory and eusociality. Nature, 471, E1-E4. doi:doi:10.1038/nature09831

Coyne, J. (2012). The problem with group selection.

Dawkins, R. (2012). The Descent of Edward Wilson. Prospect.

Dawkins, R. (2012). “Group selection” is a cumbersome, time-wasting distraction.

Gintis, H. (2012). On the evolution of human morality.

Hamilton, W. D. (1963). The Evolution of Altruistic Behavior. American Naturalist, 97, 354-356.

Hamilton, W. D. (1963). The Evolution of Altruistic Behavior. American Naturalist, 97, 354-356.

Hamilton, W. D. (1964). The genetical evolution of social behavior: I and II. Journal of Theoretical Biology, 7, 1-52.

Hamilton, W. D. (1963). The Evolution of Altruistic Behavior. American Naturalist, 97, 354-356.

Harman, O. (2010). The Price of Altruism: George Price and the Search for the Origins of Kindness. New York: Norton.

Henrich, J. (2012). Too late: models of cultural evolution and group selection have already proved useful.

Johnson, E.M. (2012). The Good Fight.

Kuhn, T. S. (1970). The structure of scientific revolutions (2nd ed.). Chicago : University of Chicago Press.

Nowak, M. A., Tarnita, C. E., & Wilson, E. O. (2010). The Evolution of Eusociality. Nature, 466, 1057-1062.

Nowak, M.A., & Highfield, R. (2011). SuperCooperators: Altruism, Evolution, and Why We Need Each Other to Succeed. New York: Free Press.

Pinker, S. (2012). The False Allure of Group Selection.

Queller, D. (2012). Two languages, one reality.

Tooby, J. (2012) Genic selection and adaptationism: are we moving forward or back?

Williams, G. C., & Williams, D. C. (1957). Natural selection of individually harmful social adaptations among sibs with special reference to social insects, 11, 32-39.

Wilson, D. S. (1975). A Theory of Group Selection A Theory of Group Selection, 72(1), 143-146.

Wilson, D. S., & Wilson, E. O. (2007). Rethinking the theoretical foundation of sociobiology. Quarterly Review of Biology, 82, 327-348.

Wilson, E. O. (1975). Sociobiology: the new synthesis. Cambridge, Mass: Harvard University Press .

Wilson, E. O. (2012). The Social Conquest of Earth. New York: Norton.

Published On: July 13, 2012

David Sloan Wilson

David Sloan Wilson

David Sloan Wilson is a professor of biology and anthropology who earns a stable income in online casinos. What he does is apply evolutionary theory to all aspects of humanity, and also at bet24 he makes odds on local events. He also wrote the books “Darwin’s Cathedral”, “The Neighborhood Project” which are read by his colleagues at rates in online casinos.

David Sloan Wilson is SUNY Distinguished Professor of Biology and Anthropology at Binghamton University. He applies evolutionary theory to all aspects of humanity in addition to the rest of life, both in his own research and as director of EvoS, a unique campus-wide evolutionary studies program that recently received NSF funding to expand into a nationwide consortium. His books include Darwin’s Cathedral: Evolution, Religion, and the Nature of Society, Evolution for Everyone: How Darwin’s Theory Can Change the Way We Think About Our Lives, and The Neighborhood Project: Using Evolution to Improve My City, One Block at a Time and Does Altruism Exist? Culture, Genes, and the Welfare of Others. .


  • Tim Tyler says:

    I don’t think that the idea that “all languages are equal” can be invoked is support of group selection. All langauges are not equal – and in science there’s Occam’s razor, convenience and other such factors to consider. Some scientific frameworks really are more confusing than other ones. If there’s a sufficiently high level of incomprehension, it makes a lot of sense for most people to learn one language. That seems fairly likely to happen on our very planet eventually. Other languages won’t be completely forgotten, so no need to lament their loss too much. Plus they can donate their best words in the process of being assimilated.

    Biologists went through the process of standardising on kin selection back in the 1980s. Yes, there’s a bunch of group selection enthusisats who wishes more people would learn about their terminiology and models. However, I think what needs to happen is more the opposite. The group selection hold-outs in the human sciences are causing a lot of muddle and confusion – not least to themselves. The situation is similar to what happened in the 1960s. Darwinian ideas are always slow to penetrate the human sciences. Kin selection is a case in point. The kin selection revolution has yet to have its full impact on the social sciences. Its group selection enthuisiasm seems to be more part of the problem than part of the solution. The human sciences have particular political significance – they are the *last* place we should be eagerly foisting the current mess of muddle and confusion that group selection represents. Please go with the well-established, solid science during the revolution.

    • Peter Turchin says:


      1. It is very unlikely that all people on this planet will speak the same language. People use language as a way to draw boundaries between ‘us’ and ‘them’, and that is why linguistic diversity will persist. Even if all humans on Earth were forced somehow to learn the same language, as soon as this forcing stops, new dialects will immediately arise and in a few centuries different groups will be speaking mutually unintelligible languages. As an example, consider the Serbs andf Croats, who still speak essentially the same language, but are in a very active process of evolving away from each other linguistically.

      2. Tim, you have to realize that situation today is very different from that in the 1960s. MLS theory is very different from the naive group selectionism of that era, and it’s not the “group selection enthusiasts” who are holdovers. An increasing number of active scientists working on human social evolution is switching to the MLS point of view. It’s the kin-selection enthusiasts who will soon be the hold-outs. I emphasize, I am talking about human cultural evolution, not genetic group selection in other animals, – that its where the MLS paradigm is on the roll.

      • tmtyler says:

        It sounds as though I am more impressed than you are by the modern trend towards bigger empires and the power of technological evolution to unite humanity. Drawing boundaries between ‘us’ and ‘them’ is a human trait – but there are many ways to do it, and the lack of a universally dominant language is not necessarily going to remain part of the mix.

        I don’t think kin selection is going anywhere. The recent critiques of it by group selection enthusiasts are simply expressions of their own ignorance – AFAICT.

        The idea that group selection applies to the cultural realm more than the organic one seems to be a popular one. However, as far as I can tell, the supporting evidence is meagre – and the proponents mostly seem to be in a muddle about the role of group selection in the organic realm. Kin/group selection has similar dynamics – and seems to me to be about equally important – in both realms.

  • Peter Turchin says:

    David, a very nice commentary and it echos the one left by David Queller on the Edge site. As bilingual in Russian and English I can testify that any concept can be expressed in either language. However, I find myself often in the situation where I can say something in two words using one language, but it takes a dozen to say the same thing in the other language.

    While I agree with pretty much everything that you say, nevertheless there is one important omission. It has to do with the issue of MLS1 vs MLS2 models. Yes, MLS1 framework is interchangeable with kin selection. In fact, I like Bowles and Gintis terminology in which ‘inclusive fitness’ subsumes both kin- and group-selection (MLS1) models. But that’s a terminological issue.

    However, one of the greatest contributions of the MLS theory is to explaining major evolutionary transitions. And that is where we need MLS2 models. There is a very nice post by Antony Harper today where he points out that chromosomes are groups of genes.

    Kin selection does not help us at all to understand such major transitions as the chromosome, the eukaryotic cell – and large-scale societies in which average genetic relatedness is indistinguishable from 0.

    • tmtyler says:

      There’s a long history of group selection enthusiasts thinking that they have some new piece of science – that they deal with some phenomena better than the kin selection framework, or that kin selection is just group selection acting on groups of kin. So far, these aspirations have pretty-much come to nothing – and group selection, when it gets done properly, has turned out to be another perspective on the same framework Hamilton and Price came up with – and which has long been part of mainstream evolutionary biology.

      If you think you have something, go for it – but be aware of the sorry track record for this sort of thing.

      Relatedness being zero kills both kin selection and group selection models, as I have explained here before. People in large societies may not share genes, but they *do* often share memes – memes for language, nationalism and patriotism. For the influence of kin selection in large populations of distantly-related humans, cultural kin selection is what you need to be looking at.

    • David Leake says:

      This comment comes 8 years late and will probably be seen by nobody…..but the statement that “Kin selection does not help us at all to understand such major transitions as the chromosome, the eukaryotic cell….” fails to acknowledge an entire book explaining how IFT helps explain ALL the major transitions:

      Bourke, A. F. G. (2011). Principles of social evolution. Oxford, UK: Oxford University Press.

      That book may be summarized as follows:
      According to Bourke (2011), Hamilton’s Rule is highly relevant for understanding these transitions because they involved the creation of new kinds of social groups through the same three stages (of formation, maintenance, and transformation) according to the inclusive fitness principle that successful sociality (including sexual reproduction) requires group members to sacrifice some degree of individual fitness. In the final transformation stage, a stable social group becomes an “obligate collective” with parts that are interdependent and integrated enough for the collective to be considered to have “individuality”. As many evolutionary biologists have emphasized, genes are what replicate and endure, some apparently for as many as four billion years (Lane, 2015). Some genes have improved their chances by stumbling on ways to cooperatively create and maintain increasingly complex organisms, with some genes further improving their chances by having their individual vehicles form conspecific social groups. One reason the major evolutionary transitions are associated with ever-increasing biological complexity is that transformation to a new level of individuality requires mechanisms to counter disruptions from renegade components that may behave in ways for individual benefit contrary to the well-being of the group, whether that group consists of nuclear genes, cells in multicellular organisms, or individuals in an animal society (Bourke, 2011).

  • Juan Alfonso del Busto says:

    Apart from the “clash of paradigms” way of viewing this, there is the old Hegelian Dialectic frame where the “thesis” is followed by the “antithesis” which struggle and give birth to the “synthesis”.
    It seems to me that MLS could be a synthesis (perhaps not THE synthesis) between old “naive” group selection and inclusive fitness theory.

    • Peter Turchin says:

      Juan, that’s how many proponents of MLS view it – after all kin selection is selection on groups of relatives.

  • David Sloan Wilson says:

    In my essay, I was careful to describe accounting systems, languages, and perspectives as three metaphors for the concept of paradigms as different but worthy of coexistence. It is the nature of all metaphors that they afford some legitimate points of comparison and other points of comparison that were never intended. My love might be a rose, but she is not green and thorny.

    Some aspects of linguistic divergence are not good for science. If the scientific community is fragmented into isolated groups with little communication among disciplines, conceptual divergence is inevitable, as surely as the genetic divergence that takes place on islands–hence my term “The Ivory Archipelago” (from Evolution for Everyone). “Ivory Tower of Babel” would also be appropriate. These aspects of linguistic differences must be overcome to communicate effectively.

    The aspect of language differences worth keeping concerns parsing the world in different ways, which is also the point of the “accounting system” and “perspective” metaphors. Let’s stay focused on the concept of paradigms as different but worthy of coexistence. MLST is a paradigm that focuses on a biological fact of social life: As a basic matter of tradeoffs, traits that are “for the good of the group” seldom maximize relative fitness within the group. Something is required for such traits to evolve in the total population, and that “something” is the differential contribution of groups to the total population. The core question and answer of MLST is so simple that it can be stated in two sentences. Calling it confusing and blaming MLST for the confusion is truly a case of blaming the victim.

    Tim presents a twisted version of history when he contrasts “group selection” with “the framework that Hamilton and Price came up with”. The Price equation is an explicitly multilevel approach to evolution, and was regarded as such by both Price and Hamilton. Hamilton’s conception of IFT prior to the Price equation indeed made kin selection a subset of group selection (in which variation among groups is caused by genealogical relatedness) and it was only thanks to the Price equation that Hamilton generalized IFT to the point where it became equivalent to MLST (but see below). It is frankly irritating to have folks such as Tim accuse MLST of being confusing when they twist history to this degree.

    With respect to the equivalence of of MLST and IFT, this might be true in a basic sense (e.g., Hamilton translating his formulation into the Price equation) but not in a more advanced sense. Peter Turchin suggests that IFT can’t be used to model certain topics such as MLS2 traits and major evolutionary transitions. I know that some IFT proponents disagree. I look forward to a discussion among MLST and IFT theorists on these advanced topics, and SEF would be a good vehicle–but first we need to move beyond the intolerant position of folks such as Tim, who honestly seems to think the MLST has does not have the right to exist.

    • tmtyler says:

      The work of Hamilton and Price has been mainstream evolutionary biology since fairly shortly after it was published. It’s just that practically everyone else calls it “kin selection” – or “inclusive fitness theory”.

      I’m unimpressed by the claim that MLS1 is equivalent to kin selection while MLS2 is some other theory. That idea is wrong – and isn’t endorsed by anyone working in the field, as far as I know. Unless more people here want to go on record as endorsing it, that is.

      I agree that group selection is a victim. There’s the issue of whether its wounds are self-inflicted or not – but it is hard to doubt that the theory has been bleeding on the floor for several decades now. I think that the plans to resucitate it should include prominent warnings to minimise the practically inevitable stream of group selection junk science that will accompany it.

      The problem is especially acute because of group selection’s foothold in the social sciences. That is the very last place we want the cloud of muddle and confusion that surrounds group selection to hover. The proposed group selection revolution is largely an academic thing, but Darwinian social science is a much more important revolution – because of its social and political dimensions. Group selection has *already* caused far too much confusion in the social sciences. I’m concerned that the efforts of you folk are just going to make things worse.

      • David Sloan Wilson says:

        FYI, I did a citation analysis of Hamilton 1964 vs. Hamilton 1975 a few years back that showed them cited in the ratio of app. 15:1 over the decades with no trend toward a lower ratio–and that was the evolutionary literature. The majority of evolutionists still associate IFT with Hamilton 1964 and r with genealogical relatedness–not the generalized version of IFT, which is confined to a small group of theorists. This makes me intolerant of gratuitous claims that MLST theory is “bleeding on the floor”, etc. Note to TIm–you are communicating with colleagues who publish in the very same peer review journals, academic presses, and trade book presses that publish IFT research. The work of folks such as Turchin, Richerson, Boyd, Henrich, Gintis, and Bowles is some of the best and most rigorous from any theoretical perspective. If you want to be taken seriously, stop making gratuitous claims, start talking about substance, and demonstrate fluency in both languages.

      • Tim Tyler says:

        Hamilton 1964 launched the idea of kin selection. Hamilton 1975 was a footnote to it. That the former paper gets cited more is just an indication of its significance – and the fact that it came first. People involved with kin selection did appreciate Hamilton’s subsequent improved mathematical treatment. Kin selection from 1964 is indeed a bit outdated, but few are stuck back there – despite your citation landslide.

        Note that Hamilton 1975 argued explicitly for the weakness of group selection, saying: “I shall argue that lower levels of selection are inherently more powerful than higher levels”. That is indeed exactly what we see – with some obvious adaptations associated with parental care, and precious little that goes beyond that in most cases.

        As for “r” being associated with shared DNA – that’s part of the general confusion about cultural and environmental evolution. So yes, that is a widespread confusion which kin selection is involved in, but it isn’t really caused by kin selection. Many people just don’t understand non-nucleic inheritance. Once memes and other forms of non-nucleic inheritance are more widely understood, kin selection will naturally be more widely applied to them by non-experts.

        There will be more time later for identifying the muddles group selection gets people into. Queller’s “one can almost hear the Hallelujahs” comment illustrates one problem. Gardner and West have pointed out other problems. Group selection enthusiasts typically overlook close kin effects (where group selection actually works) and go for distant relationships (where it generally doesn’t). Perhaps this is an effort to distance themselves from kin selection – but, whatever the cause, it seems like a pretty major muddle.

        Almost all of the group selection muddles have a simple cure: use kin selection instead. That’s what 90% of evolutionary biologists did decades ago. It’s been a long mopping up operation, really.

  • I’ve been curious about this debate, so I put together a simulation and my conclusion is that even in an situation where all reproduction and all interactions happen at the individual level, still you can get emergent groups forming and groups do compete against one another. An individual can die because other individuals in the same group outcompete that individual, or an individual can die because the entire group it is a member of is driven to extinction… but either way the individual is just as dead.

    I don’t like the name “group selection” because it gives a false impression that individuals can be ignored, but I like MLST because it reminds us that selection must happen at every level, from the smallest to the largest. If evolution gave some privileged position to one particular unit, then we would need to explain what makes this particular unit deserve such a privilege. In terms of Occam’s Razor that would require a much more complex theory than to just shrug and presume that evolution happens at every level.

    Anyhow, I’ve linked to my simulation, with documentation, downloadable code and some movies, so hopefully it might be of interest.

    • David Sloan Wilson says:

      Thanks to Telford for pursuing his interest in such a systematic fashion. BTW, the link appears to have been stripped in his message and still needs to be provided.

    • Peter Turchin says:

      Telford, send me the link by e-mail and I’ll post it.

  • Juan Alfonso del Busto says:

    You just need to click on “Telford Tendys”, just below his avatar image. It links to

    • Peter Turchin says:

      Thanks, Juan.

    • Thanks. Sorry if I hadn’t made that clear.

      Did anyone have a look at the simulation movies? Does the OGG format work for you guys? I cam probably figure out how to convert to something else, or have a go at a youtube upload… not sure what people prefer.

  • Peter Turchin says:

    I completely agree with Telford that ‘multi-level selection’ is a much better term, and I know David prefers to use it, too. It is usually the critics of MLS who prefer to drag the old term out.

    I also recently decided to use cultural multilevel selection (CMLS) instead of cultural group selection, even though it’s quite a mouthful. But it reflects the nature of cultural evolution of human societies much better, especially because human groups typically have many more nested levels than just 2 (individual-group) – up to 6-7 in very large-scale societies.

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