What’s the big deal with Nowak, Tarnita, and Wilson?

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The essence of complex life is cooperation. Genes link together to form chromosomes, cells clump together to form organisms, organisms group together to form societies. You and I are possible is because individual genes, chromosomes, and cells made a pact to work together instead of going it alone. We are also a social species. Our ancestors hung together in groups rather than pushing forth in competitive isolation.

Cooperative agreements among independent entities are so entwined with the nature of life that discovering the terms of such associations- from amoebae to ant colonies and beyond- is central to understanding how life exists in the first place. These are weighty issues, and I do not think it exaggeration to place the study of cooperation at the heart of any Grand Unifying Theory of biology.

I mention the importance of cooperation in biology because you might think that scientists who study cooperation ought show signs of being good at it themselves. But you’d be mistaken. The recent Nature paper by Nowak, Tarnita and Wilson is the latest salvo in a bitter and, in my opinion, largely pointless divide.

Biologists who study the evolution of cooperation fall into two tribes. Those who think cooperation arises primarily because it facilitates the reproduction of kin (the kin selectionists), and those who think cooperation arises because groups that cooperate do better than groups that don’t (the group selectionists). Not what you’d consider the stuff of lurid vendettas, unless of course you are already familiar with the sort of minutiae that causes academics to work themselves into a huff.

The kin selection tribe is older and better established. They’ve been productive for decades and tend to carry on with their lines of research without paying group selectionists much heed, except to issue condescending comments now and again when provoked.

The group selectionists find being ignored absolutely infuriating. They are pretty sure they’ve revolutionized Evolutionary Science, but no one notices and they have grown hoarse shouting into the void. So they write their own screeds that more or less pointedly tell the kin selectionists where they can shove their theory. Nowak et al being the latest installment.

I am giving the debate a tribal frame for a reason. When I sit down with the actual papers and models, the level of actual, quantitative disagreement falls far short of the bitter rhetoric that surrounds it. In my humble opinion, the partisans have become more interested in discrediting the other side than in advancing mutual understanding. Small statements are taken out of context and destroyed in straw-man arguments, studies are cherry-picked for rhetorical effect, quotes are mined, and the result is a downwardly tribalistic spiral as frustration grows and everyone starts to hate everyone else. A fine pickle for cooperation research if you ask me.

The reality is both groups are interested in slightly different types of questions, yet often fail to recognize this. Instead, they see the other as attempting to answer the same questions, but doing it wrong, and that ends up in confusion for everyone.

Now that I’m done placing a pox on both houses, here are a few thoughts.

Let me pick on Nowak et al for four things. First, their triumphal tone and thinly-veiled insults against colleagues throughout the paper are unprofessional, unjustified, and likely to damage their case in the long run. Framing their paper in such an adversarial tone was a mistake, as at this point they are unlikely to convince their opponents of anything. Which is a real shame, because on some counts they are absolutely correct.

Second, they pigeonholed kin selection too narrowly, making some questionable assumptions about weak selection and about what the social benefits & costs in Hamilton’s model (rB>C) really mean. This has downstream consequences not for the efficacy of their modeling of groups but for their arguments about the failure of kin selection.

Third, their use of the term “standard natural selection” is unorthodox, to say the least. What they mean is, “group dynamics modeled without a parameter tracking relatedness”.

Fourth- and this is what really kills me- they fail to understand the distinction between proximate hypotheses that explain mechanistic processes, and ultimate hypotheses that explain the more abstract population genetic conditions under which social alleles may spread. The two classes of explanations are not mutually exclusive. Kin selection is not mechanistic. It is neutral about what the social alleles actually do, merely describing whether they spread. As such, kin selection is compatible with an enormous range of mechanistic explanations about gene regulation, ecological conditions, etc. When Nowak et al propose an “alternate theory” involving nesting behavior and group formation, it merely shows that they don’t understand kin selection as an ultimate hypothesis, and hence are not in a position to critique it.

I can sympathize with this last point for historical reasons, though. Kin selection must have proven endlessly frustrating to scientists interested in detailed mechanisms of the transition of solitary to social. For example, questions about gene regulation, and about ecological context. This is because kin selection was accepted so quickly early on that it rose to a sort of undeserved hegemony, and others had to face an uphill battle against a perception that kin selection theory had already “solved” the eusociality problem. It hadn’t. It had merely provided some underlying population genetic conditions under which a new social mutation could spread. Kin selection sucked some of the air out of other potentially interesting avenues of research, creating an ambiance where resentment could fester.

Now, on to the kin selectionists. In my opinion they are logically correct but mired in reductio ad absurdum. If I want to build a model of the evolution of human populations, I don’t generally need to include terms in the model of how every individual cell in the bodies of each person relates to the other cells. One can certainly build an accurate model- even down to tracking individual atoms- but why go through all that if it is only tangential to the dynamic in question? We abstract away all the reduction as being unnecessarily redundant. Why, then, must kin selectionists insist that every model of group evolution include terms tracking the internal elements of those groups?

They hold it is because relatedness within groups drives the interactions among groups. Which it can do, some of the time. But kin selection is sometimes argued as a first principle rather than an empirically verifiable hypothesis. There are instances where such models are necessary, but there are others where they are superfluous, and it’s myopic on their part to assume that other researchers are interested in the same sorts of questions that they themselves are. Nowak et al’s model demonstrates this point well. They did, in fact, evolve theoretical eusociality without accounting for relatedness. Yet because of all the other baggage in the paper I fear this most important aspect will be ignored.

A difficult aspect for we empiricists to grasp is the extent to which the debate is about the abstractions of the best framework for building models. At least 2/3 of Nowak et al is an exposition of how their game theory math is better suited to grasping the dynamics of groups than the population genetics math of the kin selectionists, rather than an argument about what is really happening to real animals out in the real world. Think of it like programmers arguing whether Python or Perl is better language for a particular problem. It would be helpful for partisans to be able to separate arguments about the fact of what happens in the world with the opinions over which construct is preferable. Failure to understand this basic distinction is behind at least some of the miscommunication that happens among camps. David Sloan Wilson summarizes this point nicely.

I had thought that the recent papers on multilevel selection had turned the debate down a path to reconciliation and mutually agreeable recognition that not everyone was working on the same sorts of questions, and that different math might be better suited to these different questions. But apparently that view hasn’t yet caught on.

18 thoughts on “What’s the big deal with Nowak, Tarnita, and Wilson?”

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  2. Your thoughtful post was well worth waiting for, Alex.
    Your first seven paragraphs are just the right hook to get my non-entomologist friends to read the post, which is a bonus.

  3. Interesting reading.

    I would say it’s past time to stop theorizing and do the experiments. We now have the technology. All we need is a target species and someone willing to spend the [possibly long] time.

  4. Well, it is an interesting post, but I would disagree on a couple of points. First, I don’t like everything being reduced to a dichotomy. That is too simple a model – which relates to my second objection: kin and multi-level selection aren’t really theories, they are just models or groups of models. As well as all those mostly unrelated individuals who have joined a group that advocates one of these sets of models, there is the vast majority (or intelligent minority, if I am over-estimating) of biologists who don’t find either set of models especially compelling beyond very limited areas of life. Haldane, I think, is credited with some aphorism about the universe not only being stranger than we think, but stranger than with can conceive. I fall into this group when it comes to cooperation and levels of selection.

    Along these lines, I’m not sure that the concept of ‘cooperation’ is well understood, or at least it carries enough cultural baggage that it confuses more than it clarifies. Much of what you seem to refer to as cooperation, e.g. multicellular organisms, might be better understood as mutual coercion, or really, a dynamic mix of cooperation, coercion, and accident. If a lichenologist wants to be Mannichean, for example, they might say their colleagues think of lichens as either a mutualism or a fungus parasitizing an alga or two (for some reason no one seems to promote algae as the rulers of the fungi). I never understood why anyone would think that such a widespread and clearly multiply derived aspect of nature would be so easily reduced to a simple model of pluses and negatives.

    The kin selectionists do seem to have wrapped their model around their necks and thrown themselves into the abyss. Also, and probably a learned behaviour, the ‘group’ selectionists do seem to always be touchy and on the defensive. Those interested in the multi-level selection models, though, do seem to be making more progress and may some day move on to something that deserves to be called a theory, or at least a corollary to Evolution by Natural Selection, Drift, etc.

    1. Thanks for your insightful comments, Dave. I think you’ve hit on a significant point; namely, that the words we use to describe the models get tangled up with the models themselves, and different connotations in different contexts drives a great deal of the confusion.

    2. It does seem that everything can be called a theory nowadays. Nowak et al. are pretty unsure themselves on what they call a theory and what not, arguing both for and against the use of the term ‘inclusive fitness theory’.

      Great article, Alex. I absolutely agree with you. The one point where I disagree is when you say that the Nowak et al. paper explained a model for the evolution of eusociality. All I can find is a (admittedly good) model for sociality. They stop right then and there, and in one sentence they explain – basically – that reproductive division of labor and everything that goes with it are due to … group selection?!

      In the fifth and final phase, between-colony selection shapes the life cycle and caste systems of the more advanced eusocial species.

      Or am I interpreting this too harshly?

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  10. I was with you until the part where you suggested Perl might be better than Python for some tasks… 🙂

    But seriously, this is a great writeup, especially for someone like me who is not familiar with this debate. I really appreciate the context you provided. It occurs to me to ask whether you or anyone has heard of kin/group selection being applied in the marine environment? Off the top of my head, I can think of a lot of colonial animals in the ocean (corals, tunicates, siphonophores…) but none that are social like ants and bees.

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  13. People in general regularly help others in ways that don’t benefit their own genes, don’t benefit the genes of relatives, and for which they do not expect or receive a reciprocal favour. Their behaviour only benefits their own genes if others altruistically do the same which benefits society (the group) as a whole.

    I think the disagreement is over whether the above is true, not just a matter of Perl vs Python. Reciprocity is NOT the same as group selection.

  14. Thanks for a calm, rational, thoughtful review (unlike a disturbingly large number of alleged scientists).

    Why can’t it be both? Seems to me it is the interaction of gene selection and group selection that has produced modern humans as we actually are.

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