group selection

The beauty of self interest

In my review of E.O. Wilson’s The Social Conquest of Earth, I quoted this passage which captures Wilson’s conception of the origin of cooperation in humans.

Selection at the individual level tends to create competitiveness and selfish behaviour among group members – in status, mating, and the securing of resources. In opposition, selection between groups tends to create selfless behavior, expressed in greater generosity and altruism, which in turn promote stronger cohesion and strength of the group as a whole.

This passage from Matt Ridley strikes at the heart of Wilson’s dichotomy between selfishness and generosity:

“Group selection” has always been portrayed as a more politically correct idea, implying that there is an evolutionary tendency to general altruism in people. Gene selection has generally seemed to be more of a right-wing idea, in which individuals are at the mercy of the harsh calculus of the genes.

Actually, this folk understanding is about as misleading as it can be. Society is not built on one-sided altruism but on mutually beneficial co-operation.

Nearly all the kind things people do in the world are done in the name of enlightened self-interest. Think of the people who sold you coffee, drove your train, even wrote your newspaper today. They were paid to do so but they did things for you (and you for them). Likewise, gene selection clearly drives the evolution of a co-operative instinct in the human breast, and not just towards close kin.

You can read the full article here.

E.O. Wilson’s The Social Conquest of Earth

The Social Conquest of EarthThe re-eruption of the war of words between E.O. Wilson and Richard Dawkins has occurred just as I have come around to reading Wilson’s 2012 book The Social Conquest of Earth. In an interview on BBC2 (watch it at the bottom of this post), Wilson stated:

There is no dispute between me and Richard Dawkins and there never has been, because he’s a journalist, and journalists are people that report what the scientists have found and the arguments I’ve had have actually been with scientists doing research.

It is an interesting call to authority that Wilson himself challenged in his reply to Dawkins’s stinging review of the book in Prospect magazine (Wilson’s reply is at the bottom of the Dawkins piece) – or even Wilson’s statement at the end of the book that:

Science belongs to everybody. Its constituent parts can be challenged by anybody in the world who has sufficient information to do so.

Regardless, the debate between Wilson and Dawkins is a continuation of the group selection debate that has been running since the 1960s, with Wilson now on the group selection side, and Dawkins on that of the selfish gene. But despite this framing of the debate as a confrontation between two apparently diametrically opposed views, The Social Conquest of Earth suggests that Wilson’s view is somewhat more complicated, and possibly confused.

The old and new group selection

As background, it is worth defining three concepts: group selection, a newer conception of group selection called multilevel selection, and inclusive fitness.

The older form of group selection is a process where the differential survival of groups leads to the evolution of traits that benefit the group. This type of group selection, pushed in the 1960s by V.C Wynne-Edwards in particular, might involve members of a group restraining reproduction during times of scarcity so that the group does not experience resource shortages.

This concept received many harsh critiques, most famously by George Williams and in popular form by Dawkins in The Selfish Gene. The basic problem is that if someone cheats and does not restrain reproduction when others do, they will have more offspring and come to dominate the group. The altruistic trait will only emerge if groups with more altruists have a large enough advantage over other groups to compensate for their disadvantage within their groups. These conditions are generally considered to be met in limited circumstances, and most evolutionary biologists would say that the evolution of group adaptations in this way is a theoretical possibility, occurs in some circumstances, but is a practical rarity.

Group selection was somewhat reinvigorated in the late 1970s by David Sloan Wilson and friends under a reworking that is commonly called multilevel selection. The first distinguishing feature of multilevel selection is that the definition of “group” can include transitory groupings that regularly remix. You could consider two individuals who briefly trade to be a group. The second feature of multilevel selection is that selection is decomposed across multiple levels. The analysis would look at the fitness of the two trading individuals with respect to each other, which is the individual level selection, and of the fitness of their group relative to other groups.

Multilevel selection has received a largely muted response, with inclusive fitness the alternative framework preferred by Dawkins and friends – not to mention the dominant paradigm in evolutionary biology. Inclusive fitness combines the direct effects of a trait on an individual with the indirect effects of the trait on other individuals who possess that trait. Kin selection, a strategy of favouring relatives, maximises inclusive fitness.

Inclusive fitness is famously captured by Hamilton’s rule, which states that an altruistic trait will spread if rb>c. c is the cost to the altruist of the trait, b the benefits to others, and r the relatedness between the altruist and beneficiaries. A trait to favour your brother will spread if the benefits to the brother, who is 0.5 related to you, are double the costs to you. Or as J.B.S. Haldane put it, he would give his life for two brothers or eight cousins.

While apparently opposing perspectives, inclusive fitness and multilevel selection are two sides of the same coin. If you can describe an evolutionary dynamic in terms of multilevel selection, you can also give an inclusive fitness story (many suggest the two approaches are mathematically equivalent, although this is debated). They are simply different accounting methods, or languages. The intuitive explanation for the link is that higher levels of selection (the level of groups) can favour the spread of a trait because the members of that group have a degree of relatedness.

Wilson’s critique of kin selection

Wilson’s core argument through The Social Conquest of Earth is that the concept of inclusive fitness has been discredited. This claim stems from the infamous 2010 Nature paper by Martin Nowak, Corina Tarnita and Wilson on eusociality.

An E.O. Wilson drawn ant on the title page to my book

An E.O. Wilson drawn ant on the title page to my book

Eusociality involves a division of reproductive labour, such as that which occurs in the bees, ants and wasps. Eusociality and kin selection are closely linked as the higher relatedness between sisters in the bees, ants and wasps has been used to explain the willingness of most females to forgo their reproductive success for one of their sisters, the queen.

Nowak, Tarnita and Wilson’s argument was that the evolution of eusociality could be explained through simple individual selection and did not require the framework of inclusive fitness. They presented a model in which eusociality evolved without any reference to relatedness.

The model itself was interesting, but it was sandwiched between a not particularly well thought-out or supported claim that “the production of inclusive fitness theory must be considered meagre” and that it “does not provide additional insight or information” to standard natural selection theory. I will let the many responses to the paper speak for themselves, including the main response (with the 130 odd signatures – ungated version here), which contains a table indicating the contributions of inclusive fitness. But if I were to single one paper out, it is this one by Garnder, West and Wild, which addresses many of the mathematical arguments. Its main point, in short, is that Nowak, Tarnita and Wilson fail to distinguish between general kin selection theory and the kin selection methodology used to address specific problems. Their criticisms do not apply to the general theory.

Coming back to Wilson’s book, however, Wilson seems to take an even stronger stance than in the paper. For example, he states that:

Martin Nowak, Corina Tarnita, and I demonstrated that inclusive-fitness theory, often called kin selection theory, is both mathematically and biologically incorrect.

Through the book, Wilson’s characterisation of the paper’s reception has to be described as either deceptive or oblivious. Gems such as “The beautiful theory [inclusive fitness] never worked anyway, and now it has collapsed” contrasts with what even a cursory glance at the responses suggest. Nowak, Tarnita and Wilson’s critique has not generally been accepted, although reading the book gives no impression of the slightest opposition to Wilson’s position. The interview that triggered this latest spat suggests Wilson is still singing a deceptive tune. He states:

I have abandoned it [the notion of the selfish gene] and I think most serious scientists working on it have abandoned it. Some defenders may be out there, but they have been relatively or almost totally silenced since our major paper came out.

Given the paper, it is no surprise that Wilson argues throughout The Social Conquest of Earth that individual level and group selection is all that is required to explain the evolution of eusociality in insects. Wilson argues that, after the emergence of eusociality in a single colony through individual level selection, “between-colony selection” leads to the wider spread of the eusocial trait. Its selection at the individual and group levels without a multi-level selection framework. As Wilson states:

But multilevel selection, in which colonial evolution is regarded as the interests of the individual worker pitted against the interests of its colony, may no longer be a useful concept on which to build models of genetic evolution is social insects.

I have no idea why the preferred model isn’t simply a multilevel selection framework with alternative assumptions, and the confusion only increases from here.

Eusociality in humans

Where things get truly confusing is Wilson’s consideration of humans. Try as I could, I could not conceive of a sympathetic reading that would allow Wilson’s position to be seen as coherent.

First, his branding of humans as eusocial is a stretch under any definition, although he is not alone in attempting that.

But more confusingly, his argument that eusociality arose in humans due to multilevel selection is hard to understand because I have no clear idea of what he actually means. As a start, its not multilevel selection in the traditional sense, as Wilson has rejected the other side of the multilevel selection coin, inclusive fitness. Initially, I put it down to his error, but when I hit the last chapter, I realised he was using the term “multilevel selection” to mean something different. When Wilson speaks of multilevel selection, he is generally referring to individual level and group selection occurring in tandem, the “groups” being as we would traditionally define them. But then why isn’t his dynamic in eusocial insects multilevel selection under his definition?

Part of my confusion (and initial assumption) also stemmed from the contrast between Wilson’s past statements and what he wrote in the book. Compare these two paragraphs – the first from a 2007 paper co-authored with David Sloan Wilson, and the second from the last chapter of the book.

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.

Theorists of inclusive fitness themselves have argued that kin selection can be translated into group selection, even though that belief has now been disproven mathematically.

Based on this, it seems that E.O. Wilson is no longer on the same page as the number one champion of multi-level selection, David Sloan Wilson. It is particularly strange in that the two Wilsons characterise what multilevel selection means for humans in almost the same way. As E.O. Wilson writes, and I expect David Sloan Wilson would agree:

Selection at the individual level tends to create competitiveness and selfish behaviour among group members – in status, mating, and the securing of resources. In opposition, selection between groups tends to create selfless behavior, expressed in greater generosity and altruism, which in turn promote stronger cohesion and strength of the group as a whole.

E.O. Wilson’s varying use of these terms points to one of the problems group selection has in popular discourse. The term group selection has been used so inconsistently and used to refer to so many different dynamics, it is often hard to know what someone means when they refer to it. This article (ungated pdf) points to four different uses of the term “group selection”, although I have seen some suggestions that there are six different uses in the literature. When people like Wilson present their arguments in such a confusing manner, it is no surprise that others with less expertise are similarly confused. Look at Jonathan Haidt’s confusion of old group and multilevel selection as a prime example.

The other bits

Beyond Wilson’s take on group selection, there are some interesting parts to the book.

One is Wilson’s argument that many examples of kin selection can be explained as pure self interest. For example, he describes how some bird and mammal offspring remain at their parents’ nest. This has been interpreted as an example of kin selection – it helps the bird or mammal’s parents and siblings. However, Wilson suggests direct self interest is at play. In cases of resource or territory scarcity, they remain with the parents to inherit the parents’ nest when the parents fall off the perch. Wilson provides several examples of this type, suggesting that the focus on kin selection clouds the assessment of what is actually occurring.

Funnily enough, these arguments mirror an argument I often make about apparently altruistic acts sought to be explained by multilevel or group selection. Many apparently altruistic acts are self interested, such as the trade that characterises our economies. If you classed two people trading with each other as a group, as you might in a multilevel selection framework, you could class the person who gained the least surplus from the trade as an “altruist”. But the simplest explanation is that they seek to gain from trade.

The final sections of the book seek to explain “who we are”. I can only say that there are better places to read about the evolutionary origins of religion, art or language. While the last chapter of Sociobiology was revolutionary in its application of evolutionary theory to humans, the short snapshots Wilson provides in The Social Conquest of Earth do not do justice to the work that has occurred in the last 30 years. But that large body of work is, of course, one of Wilson’s great legacies. As Dawkins noted, despite The Social Conquest of Earth, Wilson’s place in history is assured.

A week of links

Links this week:

  1. An excellent Econtalk podcast with Jonathan Haidt. Just don’t buy his lines about group selection – my reasons here.
  2. Steven Pinker’s amusing article on the Ivy League. Pinker also pointed out this oldie but goodie – Bell Curve Liberals.
  3. Greg Clark applies his work on social mobility to immigration. Reihan Salam comments.
  4. A great swipe at “talent deniers”.
  5. Tracking supercentenarians.
  6. The agricultural origins of time preference – I’ll blog about this once I digest. HT: Tyler Cowen
  7. The cognitive gains from Head Start fade out by elementary school.
  8. I’m back into my habit of linking to Andrew Gelman articles every week – this time a great rant about expected utility titled “It’s as if you went into a bathroom in a bar and saw a guy pissing on his shoes, and instead of thinking he has some problem with his aim, you suppose he has a positive utility for getting his shoes wet

Economic cosmology – The invisible hand

Adam Smith’s concept of the invisible hand is one of the more abused ideas in economics. Mentioned only once in The Wealth of Nations, and only then in the context of preferring domestic to foreign industry, the invisible hand has come to represent the idea that self-interest can improve the common good. The following phrase from The Wealth of Nations nicely captures the idea of the invisible hand (although it is not located with Smith’s use of the term):

It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest.

The invisible hand has taken on a life of its own since Smith’s nuanced book, with caricatured versions espoused and attacked along the political spectrum. In that context, the invisible hand is the second Western cosmology tackled by Gowdy and colleagues in their article Economic cosmology and the evolutionary challenge from the Journal of Economic Behavior & Organization special issue, Evolution as a General Theoretical Framework for Economics and Public Policy (I covered the first cosmology – the rational man – in an earlier post).

The first point they make is that the invisible hand operates in a context of human sociality and morals. Smith would not have disagreed with that claim, with any self-interested actions constrained by the norms of the group and the morals of the individual. But as for the first Western cosmology they considered – the rational man – Gowdy and colleagues suggest that selection at a higher level is required to explain these constraints.

In arguing this point, Gowdy and colleagues draw a distinction between social and non-social behaviours. They suggest that nonsocial behaviours that do not harm others can evolve through individual level selection. However, given that adaptations at a given level require selection at that level, social behaviours that increase the fitness of someone (or their genes) should not be expected to increase the fitness of the group. For that to occur, group adaptations such as group norms are required.

There are a few of points of interest this argument, although it is not clear to me how much these are due to framing rather than substance. First, consider two people who decide to trade with each other. Each has an object the other wants, they engage in the trade and both are better off as a result. Is this a social behaviour that has increased the fitness of the group? Using a multilevel selection framing, the two traders are a group, and their group is clearly better off. One of the traders may have gained an advantage over the other due to a larger gain from the trade, so within that group, one of the traders could be considered “weakly altruistic”. So, do we consider the trade a social behaviour and the group the two traders? And if so, can I also frame this as a simple self-interested action of each party to trade for something that they want more? That is of course a feature of the multilevel selection framework – the ability to frame it in inclusive fitness terms.

A second point is the distinction between fitness and economic outcomes. In an evolutionary sense, anything that increases your fitness decreases the fitness of others. Fitness is defined in relative terms. In an economic sense, actions can make everyone absolutely better off, as in the trading example above. So when Gowdy and colleagues state that social behaviours that increase the fitness of someone should not be expected to increase the fitness of the group, this does not necessarily rule out increasing the economic benefits obtained by the group. Of course, we could also measure economic benefits in relative terms, but that is not typically what modern advocates of the invisible hand concept mean when they talk of the group benefits of selfish actions.

From their argument that group selection is involved, Gowdy and colleagues seek to resuscitate the concept of the invisible hand by suggesting that the invisible hand is selection at the level of the group. Thousands of generations of group selection (both genetic and cultural) have shaped our psychological dispositions so that now there is no need to have any conception of the group in mind when we pursue our self-interest. Our group selection shaped self-interest tends to lead to group benefits, with these self-interested actions a very narrow subset of all the varieties of self-interest, most of which do not benefit the common good.

This is an interesting argument, although I’m not sure that I buy it. I agree that the set of actions that we can undertake to advance our own self-interest are constrained by other people, social norms and institutional frameworks. For example, in many societies, uncooperative behaviour can have severe costs. Further, we exhibit many constrained behaviours even when we are not actually constrained. But as I asked in my last post, if multilevel selection and inclusive fitness are just different ways of framing the same question, what does it actually mean to say that group selection was required? If it is simply a statement that if we use a multilevel selection framework and classify the groups in a particular way, most of the action will be at the group level, then it is a relatively controversial statement. But as I read the paper, I feel that the authors mean more than this, and are actually pointing to group selection in the older sense (see my last post on the rational man for some more discussion of this distinction). In other words, for the authors, this is more than just a question of framing.

The distinction between genetic and cultural group selection is also important. Cultural group selection is less vulnerable to critiques about the mixing in human populations that genetic group selection is subject to (although it still has plenty of critics), and these need to be addressed if they are implying older concepts of group selection.

Gowdy and colleagues close the article with the suggestion that the mix of self and other regarding attitudes of humans, as shaped by individual and group selection, allow the division of labour and exchange to occur that drives economic activity. This regulation of competition and self-interest are the invisible hand that leads to the common good. In terms of how their argument should shape economic thinking, this is the practical implication – the invisible hand requires constraint. Previously provided by group selection, constraint now needs to be provided by regulation. Gowdy and colleagues do not offer further detail on this point, but this is the ultimate purpose of this evolutionary foray into economics and where some interesting debates are going to occur.

John M. Gowdy, Denise E. Dollimore, David Sloan Wilson, & Ulrich Witt (2013). Economic cosmology and the evolutionary challenge Journal of Economic Behavior and Organization, 90S DOI: 10.1016/j.jebo.2012.12.009

My series of posts on the Journal of Economic Behavior & Organization special issue, Evolution as a General Theoretical Framework for Economics and Public Policy, are as follows:

  1. Social Darwinism is back – a post on one of the popular press articles that accompanied the special issue, a piece by David Sloan Wilson called A good social Darwinism.
  2. Four reasons why evolutionary theory might not add value to economics – a post on David Sloan Wilson and John Gowdy’s article Evolution as a general theoretical framework for economics and public policy
  3. Economic cosmology – The rational egotistical individual – a post on John Gowdy and colleagues’ article Economic cosmology and the evolutionary challenge 
  4. Economic cosmology – The invisible hand (this post) – a second post on Economic cosmology and the evolutionary challenge 
  5. Economic cosmology – Equilibrium – a third post on Economic cosmology and the evolutionary challenge

I will extend the list and put up links to the other posts as I develop them.

Economic cosmology – The rational egotistical individual

In debates about group selection, the social sciences have recently become a common battleground. From Jonathan Haidt’s use of group selection to explain “groupish” traits in humans, to some of the recent rumblings about cultural group selection (as expressed in a debate triggered by Steven Pinker), and even at last years Consilience Conference, group selection has undergone a revival in the social sciences. One social science in which group selection has re-emerged is economics, with the most recent occurrence in the Journal of Economic Behavior & Organization special issue, Evolution as a General Theoretical Framework for Economics and Public Policy.

In that special issue, group selection is one of the central threads of an article by John Gowdy and colleagues, who take apart three Western “cosmologies” that the authors consider have influenced economic thought. These cosmologies are that “natural man” is a rational, self-sufficient and egotistical individual, that competition between individuals can lead to a well-functioning society, and that there exists an optimal state of nature (equilibrium). I will deal with each of these three cosmologies in separate posts, with this post on the nature of “natural man”.

Gowdy and colleagues hint at some of the previous debate over whether man is purely self-interested, pointing to the origins of the cosmology in work by Pareto, Jevons and Walras, along with critiques of this view by Edgeworth, Veblen and some modern writers. However, the bulk of the argument developed in the paper relates to the nature of groups.

Their opening argument is that group level phenomena can affect individual behaviour, which can then affect the economic system as a whole. This is a fair point, and was one of the central themes of An Economic Theory of Greed, Love, Groups and Networks that I recently reviewed. Humans are highly social and highly responsive to group-level incentives.

This point, however, leads Gowdy and colleagues to group or multilevel selection. As they frame the question:

How can natural selection favor traits that are “for the good of the group” when they are selectively disadvantageous within groups? The answer is, by a process of between-group selection. Groups of solid citizens outcompete other groups, even if solid citizens are not selectively advantageous within their own groups.

The authors note the arguments of George Williams and friends of the 1960s, who generally considered that while group level selection can theoretically occur, between group selection was invariably weak as there was too much mixing between groups. Selfish individuals within a group undermine any potential for group selection. At this point, however, Gowdy and colleagues rewrite history when they suggest that the second of these points – the weak potential for group selection – has been overturned. They go as far as stating that:

The consensus among evolutionists that humans are a highly group-selected species (as conceptualized within multi-level selection theory) challenges the individualistic assumption of economics at its core.

This is where I need to be careful with language, particularly given the mention of multi-level selection theory. The phrase “group selection” is often used in reference to selection between populations, and this was the context for the debates between Wynne-Edwards, Williams, Maynard Smith, Dawkins and others. In the mid to late 1970s, David Sloan Wilson (one of the authors of the paper the subject of this post) developed a different conception of group selection, generally termed multilevel selection, which looks at the development of individual traits within group structured populations. The groups are not population size groups, but are rather “trait groups” within populations that occur through non-random assortment of altruistic genes. These are not groups in the sense that people typically use the word. For example, when I engage in a trade with someone, we could be considered a group under this multilevel selection framework.  (I have written extended posts explaining the concept of multilevel selection here and here.)

In multilevel selection theory, selection occurs at all levels and the multilevel selection framework allows you to partition the selection effects between these levels. Importantly, multilevel selection theory is generally accepted as a different way to conceptualising the same evolutionary processes as are captured by the concept of inclusive fitness (kin selection). Gowdy and colleagues hat tip to this concept by noting that altruistic actions can be made to appear selfish by altering the frame of comparison.

But when Gowdy and colleagues flick back and forth between the group and multilevel selection terms, and particularly in their reference to Wynne-Edwards and Williams, I become confused about which group selection concept they are talking about. Are they talking about the old group selection concept as debated in the 1960s? If so, then their statement that evolutionary biologists accept that humans are a highly group selected species would be wrong. That idea appears as contested today as it ever was.

But what of the newer multilevel selection theory? Yes, biologists would agree that multilevel selection occurs in humans, although they differ in their opinion as to its usefulness as a frame of analysis. But since it is just a frame of analysis, what does it mean to say that humans are a group selected species? By using the other frame of reference, are we also a highly kin selected species?

The ability to change the frame of comparison can be seen in the examples of traits they use to illustrate that humans are a highly group selected species. We are other-regarding as to kin. There are clear benefits to self through having a social brain and the theory of mind to put ourselves in others’ shoes. And there can be huge personal benefits to being cooperative (particularly with kin).

Now, this is not to say that I do not agree with the authors’ overarching point. Despite many occasions where other-regarding considerations have been included in economics analysis (economics is a huge field with many practitioners), it does not happen as often as it possibly should. Pressures within groups, our social natures and our “groupish” traits have major effects on our actions.

But I am not certain that the multilevel selection approach is the optimal way to sell the concept that these groupish, social traits need to be considered in economic analysis. If evolutionary biologists tend to disagree on that point, are you going to be able to sell it to the economists? A starting point would be to at least get the nature of those traits on the table, present the design process from both frames of reference, and make it clear that it is not the old group selection concept that you are talking about.

As an end note, the papers in the special issue are easy to read and are not full of the usual mathematical signalling contained in economics journals. I recommend reading them yourself.

John M. Gowdy, Denise E. Dollimore, David Sloan Wilson, & Ulrich Witt (2013). Economic cosmology and the evolutionary challenge Journal of Economic Behavior and Organization, 90S DOI: 10.1016/j.jebo.2012.12.009

My series of posts on the Journal of Economic Behavior & Organization special issue, Evolution as a General Theoretical Framework for Economics and Public Policy, are as follows:

  1. Social Darwinism is back – a post on one of the popular press articles that accompanied the special issue, a piece by David Sloan Wilson called A good social Darwinism.
  2. Four reasons why evolutionary theory might not add value to economics – a post on David Sloan Wilson and John Gowdy’s article Evolution as a general theoretical framework for economics and public policy
  3. Economic cosmology – The rational egotistical individual (this post) – a post on John Gowdy and colleagues’ article Economic cosmology and the evolutionary challenge 
  4. Economic cosmology – The invisible hand – a second post on Economic cosmology and the evolutionary challenge 
  5. Economic cosmology – Equilibrium – a third post on Economic cosmology and the evolutionary challenge

I will extend the list and put up links to the other posts as I develop them.

A week of links

Links this week:

  1. Razib Kahn encourages academics to get on the blogging bandwagon (and, my post on my experience).
  2. David Barash on “evolutionary existentialism”, my favourite piece this week.
  3. Paleo or not, we all get heart disease. Also on the paleo front, Peter Turchin reviews Paul and Shou-Ching Jaminet’s Perfect Health Diet; and John Hawks reviews Marlene Zuk’s Paleofantasy.
  4. I’ve spent a lot of time over the last year or two reading material on Nowak, Tarnita and Wilson’s paper The Evolution of Eusociality, the trigger for the latest round of the group selection wars. It might be a couple of years old, but this excellent discussion by Chris Jensen is the most useful I have found. Jensen also blogs on Nowak’s work here.

Consensus in economics and biology

Despite the common public brawls, a paper presented at the American Economic Association annual meeting by Gordon and Dahl shows high levels of consensus between economists on most economic issues. Based on questions to a 41 economist panel established by the Chicago Booth School of Business, on average only 6 per cent disagree with the “consensus” answer to a question, with around 25 per cent uncertain. This observation holds for what might be viewed as relatively controversial questions, including the effect of stimulus on jobs (although the phrasing of the questions could be changed to increase dispute – such as asking whether the benefits of the stimulus outweighed the costs. Some of the questions seem benign). In some areas the consensus is weaker, such as on labour issues where 17 per cent oppose the consensus and 29 per cent are uncertain, leaving a 3 to 1 ratio between those in the majority and those against.

There has been plenty of reaction to these findings in the blogosphere (such as Noah Smith and Paul Krugman), and Justin Wolfers’s comments on the role of  ideology are worth a look. But the question in my mind is what should we consider to be a high level of consensus?

As a benchmark, a raft of climate and earth scientist surveys put disagreement among climate scientists on whether humans are behind climate change at six per cent or less.

What if we posed some questions to biologists? Group selection seems an obvious area to generate a division, but my instinct is that most professional biologists would coalesce around the same view. Advocates of the general importance of group selection are still a small minority. If we expanded the question to include cultural group selection (and similarly increased the surveyed group), we might be closer to discovering a split. However, I suspect one of the features increasing consensus in the case presented by Gordon and Dahl is that it is a small group of high-profile economists from top institutions. We could probably also increase the measured level of dispute between economists by increasing the sample to include those less tied to the middle.

Evolutionary psychology might be fertile ground for a dispute, with there still some reluctance to apply evolutionary theory to the human mind. However, I expect that it would be specific evolutionary psychology hypotheses that would be more controversial and not the general concepts. Other possible areas of dispute might be the rate of recent human evolution and the question of race, which sees some disagreement among biologists (16 per cent in the minority), although anthropologists seem more divided. On that note, I would expect a stronger split if I started quizzing anthropologists about issues such as human nature. I am also  relatively confident I could predict which anthropology faculties would be on each side of the debate.

On a historical note, would Stephen Jay Gould have been able to rally more than 10 per cent of evolutionary biologists to his side in his famous debates with Dawkins or Maynard Smith? I suspect not (is this hindsight bias from the perspective of the victors?), although he might have succeeded at exceeding that benchmark in the sociobiology debates.

In this light, it’s probably right to consider the level of consensus in economics as being strong, but to note that some of the areas have less consensus than we’d normally see in a field such as biology. Compare the consensus in economics to anthropology, however, and economists could appear quite unified.

But what of the future? Gordon and Dahl noted that consensus is generally strongest where the area in question has a larger body of literature behind it. That makes sense, but for the areas of dispute (particularly the public disputes that created the perception of a rift between economists), I don’t expect to see much short-term change. I have never been very confident on the rejection of controversial theories in economics through data and Wolfers shows evidence of ideology behind the division for some issues, so I suspect that at a minimum we may need to wait for a few funerals to occur.

Boyd and Richerson's group selection

In my review of Boyd and Richerson’s The Origin and Evolution of Cultures, I noted that I was not completely happy with their treatment of group selection. This post catalogues some of my thoughts.

Boyd and Richerson open their group selection discussion by noting that selection can be broken down into between-group and within-group selection (as per the Price equation – and given this equation can be developed for multiple levels, we refer to “multi-level selection”). But in their analysis of what they call group selection, they do not practically use this framework and there are no attempts to decompose the levels of selection despite the initial framing of the problem around the ability to do this. Part of the reason for the lack of decomposition between the levels is that Boyd and Richerson generally (but not always) have another conception of group selection in mind – differential reproduction and spread of groups. But that is part of what makes the initial framing deceiving.

This problem becomes apparent when they start to discuss situations where it is unclear at what level the selection is occurring. Take the following:

Payoff-biased imitation means people will preferentially copy individuals who get higher payoffs. The higher an individual’s payoff, the more likely that individual is to be imitated. If individuals have occasion to imitate people in neighboring groups, people from cooperative populations will be preferentially imitated by individuals in noncooperative populations because the average payoff to individuals from cooperative populations is much higher than the average payoff of individuals in noncooperative populations. Boyd and Richerson (2000) have shown that, under a wide range of conditions (and fairly quickly), this form of cultural group selection will deterministically spread group-beneficial behaviors from a single group (at a group-beneficial equilibrium) through a meta-population of other groups, which were previously stuck at a more individualistic equilibrium.

So, individuals copy people from more successful groups and the trait then spreads within those  groups. Is this actually group selection? Why does the trait spread in the new group – doesn’t this require individual advantage?

The paper referred to in this quote – Boyd and Richerson (2000) – is also contained in the book, and it describes a model with the spread of norms about drinking. Drinking has negative long-term consequences, but some people drink due to strong discounting. However, the presence of people with puritanical (rather than tolerant) norms can increase the cost of drinking due to social disapproval, meaning populations with puritan norms are better off as a whole than populations of tolerant people.

As people with tolerant and puritanical norms get on each other’s nerves, an isolated group’s members will tend to have the same norm. But given the lower number of drinkers in the puritan groups, the puritan groups will have the higher total payoff. Thus, if groups can mix, the puritan norms may spread as people copy the most successful individuals from other groups. Boyd and Richerson describe this as group selection, but the spread of the norms within groups after mixing demonstrates a degree of individual benefit. At what level are the dynamics dominant?

In other parts of the book, it is difficult to disentangle what the trait under group selection is. For example, when Boyd and Richerson write of the spread of ritualised cannibalism in New Guinea and the associated spread of the disease kuru, they describe the process as group selection. But is the relevant cultural trait eating kuru? Conforming to group rituals? Conforming to rituals concerning cannibalism? Which of these is being selected affects the assessment of the level of selection. Educated guesses can be made, but it is hard work.

These examples indicate a degree of looseness in Boyd and Richerson’s use of the term group selection. At times the term seems to be thrown at any dynamics that involve groups, with no clear definition of what group selection is and no attempt to place the observed behaviour in the context of the definition. This is, of course, a broader issue in much of the literature concerning group selection.

Having said this, as I mentioned in my review, I am not averse to the idea of examining cultural evolution in a group selection framework. I like many of Boyd and Richerson’s models and the descriptions of the dynamics, even if I consider the group selection label has been incorrectly applied. And it is possible that some of my complaints above could be dealt with through better explanation. But Boyd and Richerson use the term group selection so loosely that it is hard to agree with their use, particularly as I’m not sure what exactly I would be agreeing with. For the moment I prefer to describe their overall approach as “cultural group dynamics”.

Boyd and Richerson's The Origin and Evolution of Cultures

The Origin and Evolution of CulturesWhen I asked for suggestions for my evolutionary biology and economics reading list earlier this year, Boyd and Richerson’s The Origin and Evolution of Cultures was one of the most recommended. Their exploration of cultural evolution has many elements that are relevant to economics, including the development of institutional frameworks, the evolution of cooperation and the transmission of technology.

The book comprises 20 papers (published between 1987 and 2003) that are grouped into five thematic groups: the evolution of social learning; ethnic groups and markers; human cooperation, reciprocity and group selection; archaeology and culture history; and links to other disciplines. Each chapter was a stand-alone paper, so rather than going into any of them in further detail, I will save that for some later posts and give some more general observations here.

First, Boyd and Richerson are clear in arguing that “culture” is a distinct feature from “environment”, and that it should be examined through an evolutionary lens:

[C]ultural variation is transmitted from individual to individual, it is subject to population dynamic processes analogous to those that effect genetic variation and quite unlike the processes that govern other environmental effects. Combining cultural and environmental effects into a single category conceals these important differences.

Having been sceptical before reading the book, this is one issue on which I am a convert. I am still not convinced that it is always (or often) possible to identify practically which cultural trait is subject to selection or to differentiate it from the environment, but drawing this distinction led to some interesting and parsimonious models. Further, an evolving cultural trait may be the environment for another cultural trait.

Their exploration of cultural evolution often contains a genetic element, usually in the context of “gene-culture coevolution”. For example, they describe a process whereby cultural institutions might result in people with certain genetic predispositions beings weeded out.

Mechanisms by which cultural institutions might exert forces tugging in this direction are not far to seek. People are likely to discriminate against genotypes that are incapable of conforming to cultural norms (Richerson and Boyd, 1989; Laland, Kumm, and Feldman, 1995). People who cannot control their self-serving aggression ended up exiled or executed in small-scale societies and imprisoned in contemporary ones. People whose social skills embarrass their families will have a hard time attracting mates. Of course, selfish and nepotistic impulses were never entirely suppressed; our genetically transmitted evolved psychology shapes human cultures, and, as a result, cultural adaptations often still serve the ancient imperatives of inclusive genetic fitness. However, cultural evolution also creates new selective environments that build cultural imperatives into our genes.

However, Boyd and Richerson’s exploration of gene-culture coevolution does not usually extend to developing models with where genes and culture simultaneously evolve. At times this is problematic, particularly where they incorporate cultural group selection into the picture, as it can be difficult to understand how the process would actually work from the often loose verbal descriptions. Conversely, a model incorporating these multiple evolving elements would lose the clarity and simplicity that allows most of the models in the book to be useful.

The indeterminate nature of the culture-environment distinction I alluded to above is also highlighted by this gene-culture evolution quote. Cultural evolution creates new selective environments. While a cultural trait is evolving, it is effectively creating an environment in which other cultural traits or genes evolve. This is similar to the idea that genes effectively create the environment in which other genes evolve, whether those other genes be in the same individual or in other individuals and species.

Boyd and Richerson’s work shares some similarity with that of Sam Bowles and Herb Gintis, particularly in their approach to model development. Simulations are used as illustrations, the focus is more on demonstrating ideas than providing hard proofs, and agent based models are a common tool.  However, Boyd and Richerson have a stronger sense than Bowles and Gintis of the limitations of their models, and generally recognise their illustrative and not determinative nature. Bowles and Gintis have a habit of making a model and arguing that, since a certain feature didn’t work in their model (such as the evolution of cooperation by reciprocal altruism), their model is evidence that it can’t work at all. The problem with this approach is that the model only examines such a small subspace of the possibilities. Boyd and Richerson tend to be more constrained in their conclusions, although not always so.

One of the groups of papers focuses on group selection. I am more open to analysing the transmission of cultural traits through the lens of group selection (or multilevel selection) than I am for the transmission of genes, largely because cultural group selection is not necessarily undermined by migration between groups in the same way as genetic group selection. Boyd and Richerson note this when they state:

[S]ocial extinction does not mean physical elimination of the entire group. Quite the contrary, most people survive defeat but flee as refugees to other groups, into which they are incorporated. This sort of extinction cannot support genetic group selection because so many of the defeated survive and because they would tend to carry their unsuccessful genes into successful groups, rapidly running down variation between groups. However, the effects of conformist cultural transmission combined with moralistic punishment makes between-group cultural variation much less subject to erosion by migration and within-group success of uncooperative strategies than is true in the case of acultural organisms.

However, I am still not convinced that the cultural group selection approach provides the clearest method of analysis. I’ll save my specific issues with their approach in a separate post.

My favourite chapter of the book was the least theoretical. Boyd and Richerson (with Joseph Soltis) asked whether observed rates of group extinction could be sufficient for group selection to drive rapid cultural evolution. Based on an examination of hunter-gather tribe extinction rates, they concluded that group selection could not be responsible. It was refreshing to see some empirical analysis applied to this issue. For all the noise around group selection (both genetic and cultural), it is rare that the debates are accompanied by increasingly available data.

*My later post with my thoughts on their approach to group selection can be found here.

Haidt's group selection

Having given my thoughts on Haidt’s generally excellent The Righteous Mind in my last post, I want to turn to Haidt’s use of group selection in the last third of his book. The central themes of his book don’t rest on group selection (in my opinion), but Haidt is at the centre of the reemergence of group selection in the social sciences and his points are worth discussing.

Haidt uses the more modern phrase “multilevel selection” in addition to “group selection” through the book. Multilevel selection refers to a method of accounting for selection at the different levels (e.g. the gene, individual, group etc.), while the older concept of group selection usually refers to natural selection between groups and the evolution of group-level adaptations. Multilevel selection also involves what are called “trait groups”, which may briefly form and break up, compared to the rigid reproducing groups of the old group selection.

It seems that Haidt has a reasonable grasp on these distinctions but his use of the term multilevel selection is often confusing. For example, he keeps using the phrase “product of multilevel selection”. But multilevel selection is, as the name suggests, selection at different levels. You can look at a scenario through a multilevel selection framework and conclude that all the selection occurs at the level of the gene or individual. Multilevel selection and inclusive fitness are just different accounting methods (or languages). It is not a case that one happens and the other doesn’t. What Haidt is implying, and the way he should state it, is that selection is occurring predominantly at the level of the group. Based on some passages of the book, it is clear that Haidt understands this, but at other times his language is loose.

When Haidt argues for the importance of selection at the level of the group (I’ll refer to it as group selection for rest of this post), he offers four lines of evidence: the role of group selection in the major evolutionary transitions; the shared intentionality of humans; gene-culture evolution; and the potential for fast evolution.

The major evolutionary transitions, such as the emergence of eukaryotic cells from the combination of bacteria, are one of the few areas where many evolutionary biologists will agree that group selection occurred. Haidt characterises the major evolutionary transitions as times where methods to control freeriding evolved at one level, allowing superorganisms to arise at the next. Haidt then follows in the footsteps of biologists such as David Sloan Wilson and E. O. Wilson and argues that the evolution of “ultrasociality” in humans is a similar transition.

I don’t want to rehash this argument in-depth, but it goes back to the classic group selection debate. In the evolutionary transitions of the past, a reproductive bottleneck was present. Once two bacteria are combined in a cell, the only way they can reproduce is if the “group” reproduces. But that bottleneck does not exist in human groups, so there is opportunity for freeriding. We then get to the old debate about the level of freeriding and whether the level of group extinction and the degree of gene flow between groups allows group selection to outweigh this freeriding.

While Haidt follows in others’ footsteps in referring to the major evolutionary transitions, his other arguments are more his own. On shared intentionality, Haidt argues that the ability to share intentions between people allows collaboration, the division of labour and shared norms. While Haidt claims this is group selection, this is a case where the multilevel selection framework should be properly applied. How much benefit does one get as an individual from understanding what someone else is thinking, versus the benefit you get from pairing with someone who also has that ability and working together to succeed as a group? While having more people in your group who are able to share intentions will help you defeat other groups, shared intentionality is clearly beneficial to an individual. Being in a group of mind readers when you have no idea what is going on is suboptimal. Which level the selection predominantly operates at needs to be analysed (and will depend upon assumptions about what makes up a group). This is the type of scenario that I have argued before is simpler to analyse in an inclusive fitness framework.

Haidt’s third line of evidence is a somewhat confusing take on gene-culture evolution. Haidt argues that cultural group selection supported “prototribalism”, which led to an environment that then supported genetic evolution. However, Haidt’s examples do not sound like group selection. For example, Haidt writes:

[I]ndividuals who found it harder to play along, to restrain their antisocial impulses, and to conform to the most important collective norms would not have been anyone’s top choice when it came time to choose partners for hunting, foraging, or mating. In particular, people who were violent would have been shunned, punished, or in extreme cases killed.

This sounds like individual level selection against violent, non-conformist individuals. I am not sure why Haidt was so keen to covert Boyd and Richerson’s arguments on cultural group selection into genetic group selection, but try he did.

Haidt’s biggest reach, however, comes with his argument that the potential for fast evolution supports group selection. Haidt notes that gene-culture evolution reached fever pitch in the last 12,000 years, and that is an assessment I would agree with. He refers to the group selection experiments conducted by William Muir, in which Muir rapidly improved egg laying by selecting groups of successful chickens (achieved, of course, through the effective creation of a reproductive bottleneck in the experimental design). Haidt then pushes the rapid evolution argument to the limits when he seeks to implicate group selection in the emergence of religion. As large-scale religion only emerged since the dawn of agriculture, Haidt suggests the rapid recent evolution identified by the likes of John Hawks, Greg Cochrane and Henry Harpending provides scope for recent group selection. He writes:

[G]roup selection can work very quickly (as in the case of those group-selected hens that became more peaceful in just a few generations). Ten thousand years is plenty of time for gene-culture coevolution, including some genetic changes, to have occurred. And 50,000 years is more than plenty of time for genes, brains, groups, and religions to have coevolved into a very tight embrace.

The problem is that group extinction and reproduction generally occurs more slowly than individual level selection. At the individual level, we see large differences in fertility every generation. For many people, it is the end of the genetic line. To the extent heritable traits underlie this variation, we can see rapid changes in genotype. In contrast, studies of rates of group extinction suggest it is slow. Further, groups tend not to be simply wiped out, but the “loser” groups tend to merge into the victor, bringing their genes with them.

Having said all this, we might be able to build a multilevel selection model in which we allow temporary religious or other “trait groups” to form and break up in short periods and divide the degree of selection between the various levels. However, I still doubt we will see significant selection at the group level for most of these examples and I don’t feel that this was the sort of group selection Haidt was interested in. Further, I expect the inclusive fitness framework would give a clearer picture. If this trait group approach could have provided a stronger argument, Haidt might have used it.