Richard Wrangham’s newest book, The Goodness Paradox, gets a lot right. The central thesis is that we are a self-domesticated species. We have bred ourselves for tameness, in the same way that we have bred our animal companions. The opposite of tameness is reactive aggression, or the tendency to lash out in a social confrontation. But there is another kind of aggression, the cool, calculated kind called proactive, that is also a hallmark of our species. Hence “the strange relationship between virtue and violence in human evolution”, which is the book’s subtitle.

The idea that we are a self-domesticated species has long roots but is experiencing a renaissance based on a now classic study of silver fox by the Russian scientists Dmitri Belyaev and Lyudmila Trut. The story is beautifully told in the book How To Tame a Fox and Build a Dog, co-authored by Trut and Lee Alan Dugatkin, who happens to be one of my former PhD students. Not only could tameness in silver foxes be selected in only a few generations, but a whole suite of other behavioral, physical, and life history traits also evolved as byproducts. Moreover, the same package of traits appears to evolve in all domesticated species. Thus, an important secondary theme of Wrangham’s book is that not all products of evolution require separate adaptive explanations, a point stressed by Stephen Jay Gould and Richard Lewontin in their classic “spandrels” article in 1979[1].

The existence of an entire syndrome of traits associated with domestication provides ways to test the hypothesis of self-domestication in humans and other species, such as bonobos vs. chimpanzees and species that inhabit islands compared to their continental ancestors. This allows Wrangham to be quite precise about when human self-domestication evolved. It is a hallmark of our entire species, Homo sapiens, compared to all other species in the Homo genus. Arguably, self-domestication is the reason why our species replaced those other species.

As one of the pre-eminent thinkers about primate and human evolution, Wrangham does an excellent job addressing all four questions that must be asked to fully explain any product of evolution, concerning their function (if any), phylogeny, mechanism, and development[2]. He is also one of the most lucid writers for a general audience. Hence, I warmly recommend The Goodness Paradox to experts and laypeople alike. I learned a lot from it and think that you will also.

But there is one thing that Wrangham gets wrong. He thinks that he can develop his thesis without invoking group selection, when he is invoking group selection in every way except using the words.

Group selection is the evolution of traits based on the differential survival and reproduction of groups in a multi-group population, as opposed to the differential survival and reproduction of individuals within groups. It is famously controversial. Among the scientists cited by Wrangham — such as John Alcock, Richard Alexander, Scott Atran, David Barash, Paul Bingham, Christopher Boehm, Samuel Bowles, Elizabeth Cashdan, Timothy Cluttonbrock, Leda Cosmides, Jerry Coyne, Paul Crook, Martin Daly, Richard Dawkins, Lee Dugatkin, Frans de Waal, Andrew Gardner, Herbert Gintis, Ashley Griffin, Jonathan Haidt, Marc Hauser, Joseph Henrich, Robert Hinde, Dominic Johnson, Martin Nowak, Daijiro Okada, Steve Pinker, Anne Pusey. Matthew Ridley, Robert Sapolsky, Michael Shermer, Elliott Sober, Corina Tarnita, Ian Tattersall, Michael Tomasello, John Tooby, Carel van Schaik, Stuart West, E.O Wilson, Margo Wilson, and Robert Wright–some rely heavily upon group selection, others reject it, and still others treat group selection as equivalent to other theories of social evolution, the difference being a matter of perspective rather than the invocation of different causal processes[3].

****

Before critiquing Wrangham’s treatment of group selection, it is important to be precise about the definition of terms. The best way to do this is to briefly review what all theories of social evolution share in common.

Consider the evolution of a nonsocial trait such as coloration in desert living species. Individuals vary in their coloration, those that match their background are more fit, and coloration is partially heritable. The result: individuals that impressively match their background.

Now consider the evolution of a social trait such as docility and aggression. Aggressive individuals pick fights with others while docile individuals avoid fights. To model the evolution of these alternative traits, we must assign fitness values to them. But, unlike solitary traits, we cannot do this solely on the basis of their individual properties. The fitness of either type depends upon the other individuals with whom they socially interact. This makes the study of social behavior more complicated than the study of solitary traits.

Any study of social evolution must say something about the structure of social interactions.

This is true for a verbal model, a mathematical or computer simulation model, or an empirical study that aims to understand how social behaviors evolve. However, mathematical and computer simulation models have the virtue of being precise about their assumptions. For example, N-person game theory assumes that individuals socially interact in groups of size N. The fitness of any individual depends upon its trait value (such as aggressive vs. docile) and the trait values of the other members of its group. The simplest N-person game theory models assume a very large number of groups, the random distribution of individuals into groups, and the dissolution of the groups after a single round of social interactions.

Elaborated models consider non-random distributions of individuals, multiple interactions within groups, different patterns of dispersal, and so on. The details depend upon the biological details of the organism being modeled. If the real organisms interact in pairs, then only 2-person game theory will do. If they interact with genetic relatives or with partners chosen on the basis of previous experience, then the assumption of random interactions won’t do. If the groups persist indefinitely and trade a fraction of dispersers every generation, then the assumption of ephemeral groups won’t do. It is the biology of real-world organisms that decide the details of any given model!

No matter what the details, all models of social evolution share the following features.

1) The sets of socially interacting individuals that influence each other’s fitness (the N in N-person game theory) are small compared to the total evolving population. This means that most evolving populations are populations of groups in addition to populations of individuals within groups—such as fish schools, bird flocks, primate troops, and human tribes. Sometimes the groups have discrete boundaries but sometimes they are neighborhoods, such as plants that interact only with their immediate neighbors. The important common denominator is social interactions that are local compared to the size of the total evolving population.

2) Selection among individuals within each group tends to favor traits that would be called disruptively self-serving in human terms, such as aggression compared to docility. In N-person game theory, virtually all of the traits called altruistic or cooperative are selectively disadvantageous within the groups of size N. Even the tit-for-tat strategy of 2-person game theory, which starts out nice and thereafter imitates the previous play of its partner, never beats its partner and can only lose or draw.

3) If social traits that are variously called altruistic, cooperative, mutualistic, and prosocial cannot evolve by within-group selection, then they require the differential survival and productivity of groups in a multi-group population. As I put it in my 2007 article with E.O. Wilson titled “Rethinking the Theoretical Foundation of Sociobiology”, selfishness beats altruism within groups, altruistic groups beat selfish groups, and everything else is commentary[4]. In 2-person game theory, pairs of altruists do better than mixed pairs, which in turn do better than pairs of selfish individuals. This between-group advantage for altruism can override its within-group disadvantage, especially if the distribution of individuals into groups is above-random.

Notice that these three features apply to all models of social evolution, no matter what they are called. Moreover, all models of social evolution must conform to the biological details of the social traits being modeled. Otherwise they will simply arrive at the wrong answer. The definition of groups and the larger population structure whereby groups are formed and dissolve are not arbitrary. They must be tailored to each and every social trait being modelled. This is why I coined the term “trait-group” in my first article on group selection in 1975[5].

Against this background, we can define “individual selection” as “selection among individuals within groups” and “group selection” as “selection among groups in a multi-group population”. These are the definitions that are used in virtually all explicit group selection models. They also capture what Darwin meant when he famously wrote “although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an advancement in the standard of morality and an increase in the number of well-endowed men will certainly give an immense advantage to one tribe over another[6].”

****

Now I am in a position to advance my claim that Wrangham rejects group selection in his own mind but invokes it in every way except using the words when developing his thesis. He directly discusses group selection three times in the main text. The first is when he describes a theoretical model of warfare by Jung-Kyoo Choi and Samuel Bowles (location 2410 of the kindle edition)[7]. The details need not concern us, other than to say that they conform to Darwin’s scenario and the three features of all models of social evolution just listed. Wrangham accepts it as a group selection model but rejects it for not getting the biological details of human warfare in hunter-gatherer groups right. Fair enough. I have myself stressed that the model must match the biology.

The second mention of group selection is in the following passage (3763):

Group selection theory suggests that self-sacrifice by an individual can be favored over evolutionary time if it provides sufficiently large benefits to the individual’s group, which normally means a social breeding unit such as a hunter-gatherer band. Very often, however, the group that benefits from an individual’s generosity is not a social breeding unit. As Robert Graves’s recollection of his school days reminds us, the beneficiaries might be only a subgroup of a given social network. In the group as a whole, moral behavior might benefit some individuals at the expense of others.

Robert Graves’s recollection was of his school days, where he and his friends would never cheat on each other but thought nothing of cheating on their teachers. Here, Wrangham assumes that group selection models have some fixed definition of groups, as opposed to being defined in reference to each trait. For behavior expressed among school chums, the group of chums is the salient group.

Here is Wrangham’s third mention of group selection (5002):

Group selection is commonly invoked to explain our species’s interest in nonrelatives and our occasional willingness to sacrifice our own interests on behalf of a larger good. Group selection theory, however, has never quite been able to explain how benefits at the group level override those of individuals. The theory that the moral senses evolved to protect individuals from the socially powerful suggests that group selection might be unnecessary for explaining why we are such a group-oriented species. Our deference to the coalitionary powers within our own groups leads to a reduced intensity of competition, enabling groups to thrive.

This passage contains two errors. The first is to suppose that the counterforce to within-group selection is mysterious, nebulous, or necessarily weak. This is certainly not the case for formal mathematical and computer simulation models, where between-group selection is as precisely specified as within-group selection. As we shall see, it isn’t true for verbal models or empirical studies of social behavior either.

The second error is for Wrangham to assume that his own way of thinking described in the second half of the paragraph differs from his description of group selection in the first half. Let’s consider his own account in more detail.

****

Wrangham is not a mathematical or computer simulation modeler, but that doesn’t matter. At the beginning of this essay I stated that any study of social evolution must say something about the structure of social interactions. Formal models have the virtue of being precise about their assumptions, but verbal models based on extensive field experience have the virtue of being realistic—the kind of realism that should be the starting point of the more formal models.

Let’s begin with the behavior of chimpanzees, which Wrangham has studied extensively in the wild. Populations are subdivided into communities of a few dozen individuals. Males remain within their natal groups while females move. Males defend the boundaries of their territories against the males of adjacent communities.

Some behaviors expressed by individuals have an impact on the whole community. However, other behaviors are more limited in their impact, such as dyadic interactions or competing cliques within the community. Thus, the community is not a one-size-fits-all group for chimpanzees, any more than a band is a one-size-fits-all group for hunter-gatherers.

Despite these complexities, some chimpanzee behaviors are easy enough to interpret from a multilevel evolutionary perspective. Take reactive aggression for example. It is far, far more common in chimps than in human groups and clearly benefits the aggressor compared to other members of the same community. It is a form of disruptive selfishness, favored by within-group selection, pure and simple.

While humans are far less reactively aggressive and far more proactively aggressive than chimps, chimps do display proactive aggression to a degree, especially in their behavior directed against members of other communities. Here is one example described by Wrangham (4149).

In a few primate species (such as chimpanzees), infanticide occurs for reasons other than sexual selection. Male chimpanzees who encounter mothers from neighboring communities tend to attack them and can severely wound or kill their small infants. In this case, the protagonists are unlikely to meet again, so there is little chance of the killer’s fathering the female’s next infant. The traditional sexual selection theory, therefore, does not apply. Possibly, the killers benefit by intimidating the female into avoiding the area, leaving more food for the killer’s community. Alternatively, the attackers might gain by killing male infants that would otherwise grow up in the neighboring community to become future opponents. Further observations will eventually test ideas.

Let’s give Wrangham the benefit of the doubt and assume that his interpretation is correct. In the traditional sexual selection theory of infanticide, males that kill infants within their own community father more offspring than males who don’t. That’s a case of disruptive within-group selection pure and simple, which is bad for the group. But harming a female from another community is a different matter. The benefits do not flow to the males inflicting the harm, but to their entire community, in the form of an expanded territory and fewer males in the adjacent community.

The same is true for killing adult males of adjacent territories, as described by Wrangham in this passage:

The attacks cost little for the attackers, but by eliminating rivals they benefit their own community. In Kibale’s Ngogo community, John Mitani and David Watt’s team recorded instances when males killed or fatally wounded eighteen members of neighboring communities during period of ten years. The Ngogo community then expanded their territory into the area where most of the kills occurred. In Gombe, Anne Pusey and her colleagues have shown that, when the territory occupied by a community increases in size, community members are better fed, breed faster, and survive better. Kill some neighbors, expand the territory, get more food, have more babies—and be safer at the same time, since there are fewer neighbors who might be able to attack you.

If Wrangham is correct in his interpretation, then by his own account he is describing a case of between-group selection. The proactively aggressive behavior provides a benefit for the whole community at a cost to the aggressors. Wrangham makes much of the fact that the individual cost of killing is not large because many are ganging up against one. Still, the cost is probably something and even if it was zero the proactively aggressive behavior would be neutral with respect to within-group selection. The benefit remains at the group level. The fact that the cost of providing a group-level benefit is low makes group selection plausible, because it is not strongly opposed by selection within groups.

Notice also that Wrangham is able to describe the group-level benefits as clearly as the individual-level costs. There is nothing mysterious, nebulous, or necessarily weak about expanding the territory of a community over a period of years.

To summarize, even before we get to human self-domestication, Wrangham is explaining reactive aggression as a product of within-group selection and proactive aggression as a product of between-group selection in chimpanzees. In the latter case, he is invoking group selection in every way except using the words.

*****

Before proceeding to the human case, it is necessary to return to theoretical models. I have already shown that modelling the evolution of social behaviors is more complicated than modeling the evolution of solitary behaviors. Modeling the evolution of social control mechanisms is more complicated still.

Let’s begin with a standard model of altruism and selfishness in an N-person game theory model. Now let’s introduce a second trait. Some individuals punish selfish members of the group, while others allow selfishness to go unpunished. This creates four combinations of individuals in any given group: selfish punishers (SP), selfish non-punishers (SN), Altruistic punishers (AP), and altruistic non-punishers (AN). If there are enough punishers in a group, then selfishness no longer beats altruism. However, non-punishers enjoy the benefits of social control provided by the punishers without paying the cost. We haven’t solved the problem of altruism, but merely relocated it from the originally altruistic trait to the punishment trait. A rich literature exists on this topic using phrases such as “altruistic punishment” and “second-order public goods”. One fascinating result explored by another of my former PhD students, Omar Eldakar, is that of the four combinations of individuals, group selection can result in a mix of selfish punishers and altruistic non-punishers. Altruistic punishers go extinct because they pay a double cost—the cost of being an altruist and the cost of being a punisher. Selfish non-punishers are held at a low frequency by the selfish punishers. It’s as if the benefits of selfishness become a payment for the cost of being a punisher[8]!

Against this background, we can consider the central premise of Wrangham’s book; that self-domestication evolved in our species because individuals who could not control their aggressive impulses were executed. Or more precisely, execution is a necessary arrow in an entire quiver of social control mechanisms that begins with mild sanctions such as gossip and escalates as needed.

Based on what I have said about social control mechanisms as second-order public goods, it should no longer surprise the reader that the many examples provided by Wrangham invoke group selection in every way except using the words. Here is one example (2251).

Prior to Homo sapiens, Marean suggests, humans lived at low density in small societies, like chimpanzees. Then one population, which he thought might have lived on the southern African coast, developed an ability to gather and hunt so well that their food resources became far more productive. The population naturally grew to the point where there was competition over the food supply, and soon groups were fighting over the best territories. Success in war became imperative. Groups accordingly allied with one another, giving rise to large societies of the type that hunter-gatherers form today. Cooperation among warriors within groups was so vital for winning conflicts that it evolved to become the basis of humans’ exceptional propensity for mutual aid. Sociality became more complex, learning became more vital, and culture became richer.

Could there be a more clear description of group-level selection? It is little different from Darwin’s original speculation or the intent of the Choi and Bowles model of warfare. Wrangham makes much of the fact that with the advent of language and weaponry, punishing deviant behavior became so effective that groups became “a tyranny of cousins” (2777) and “like a boardroom without a chairman” (2802) in enforcing their norms. He can’t seem to see what every model of social control concludes: the lower the cost of punishment, the stronger between-group selection is relative to within-group selection.

*****

The reason that I listed forty-one scientists by name at the beginning of this essay is to stress the magnitude of the problem that I have examined in detail for Wrangham’s book. Every one of those authors discuss the three features shared by all models of social evolution in their writing. They have no choice if they want to be biologically realistic. Some of the authors recognize between-group selection when they see it, including Christopher Boehm, who pioneered the concept of reverse dominance as an important factor in human evolution. Peter Turchin, whose 2014 book Ultrasociety: How 10,000 Years of Warfare Made Humans the Most Cooperative Species on Earth covers much of the same ground as Wrangham’s book, says this: “The central breakthrough in this new field is the theory of cultural multilevel selection.”

Other authors on the list, like Wrangham, manage to describe group selection as a failed concept even when it is staring them in the face. My respect for Wrangham and praise for The Goodness Paradox in every other respect is genuine, but someday historians will look back in wonderment as to how otherwise smart people, who were part of the same scientific community, managed to remain so divided in their own minds about the importance of group selection in human evolution.

References:

[1] Gould, S. J., & Lewontin, R. C. (1979). The spandrels of San Marco and the panglossian paradigm: A critique of the adaptationist program. Proceedings of the Royal Society of London, B205, 581–598.

[2] These are known as “Tinbergen’s four questions” based on this article by the Nobel laureate Niko Tinbergen: Tinbergen, N. (1963). On aims and methods of ethology. Zeitschrift Für Tierpsychologie, 20, 410–433.

[3] For more on equivalence, see Chapter 3 of my book: Wilson, D. S. (2015). Does Altruism Exist? Culture, Genes, and the Welfare of Others. New Haven, CT: Yale University Press.

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

[5] Wilson, D. S. (1975). A general theory of group selection. Proc. Natl. Acad. Sci., 72, 143–146.

[6] Darwin, C. (1871). The descent of man and selection in relation to sex (Vol. 2 vol.). London, UK: John Murray. In addition, see my conversation with Elliott Sober titled “Was Darwin a Group Selectionist?”: https://evolution-institute.org/was-darwin-a-group-selectionist-a-conversation-with-elliott-sober/

[7] Choi, J.-K., & Bowles, S. (2007). The Coevolution of Parochial Altruism and War. Science, 318(5850), 636–640. https://doi.org/10.1126/science.1144237

[8] Eldakar, O. T., Farrell, D. L., & Wilson, D. S. (2007). Selfish punishment: altruism can be maintained by competition among cheaters. Journal of Theoretical Biology, 2007, 198–205.

Published On: May 10, 2019

David Sloan Wilson

David Sloan Wilson

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. .

8 Comments

  • Brian Wood says:

    I really enjoyed this essay and think you are doing a great service by mapping Wrangham’s thesis to the theoretical framework of multi-level selection. I would like to ask however how you justify this claim: “Wrangham is explaining … proactive aggression as a product of between-group selection in chimpanzees.“ Your depiction of between-community violence in chimps rightly identifies that benefits from territorial expansion are received by all group members- the protagonists as well as fellow group members. But this does not seem to be sufficient evidence to claim that the aggression is ‘a product of between-group selection’. This could be so. But don’t other possibilities bear consideration? The fact that there are group level benefits and some individual costs doesnt seem sufficient, because there are also individual benefits. Couldn’t this just as well be a case in which individual- level cost/benefit accounting makes the aggression adaptive (small cost to carry out, some increase in future survival and reproduction prospects)? Or a case in which both individual and group level benefits align and underlie the trait’s evolution? The third option you advance- that it is a product of (only?) between group selection seems to require more substantiating evidence. Are there bridging assumptions that you could elaborate? I think this discussion could be useful because the study of group selection in humans is more complex, owing to cultural inheritance, but the chimpanzee case is biologically ‘easier’ to model, and we have enough long term research at these field sites to test predictions derived from these hypotheses. Thank you for you essay.

    • David Sloan Wilson says:

      Dear Brian–Your comments provide an opportunity to discuss equivalence, or multiple ways of accounting for evolutionary change. Let’s begin by accepting Wrangham’s description of the biology: Chimps that kill or harass members of other communities provide benefits to their whole community at some personal cost–if only a cost of time and effort. When we do a set of nested fitness comparisons–between individuals within groups, between groups in a multi-group population, we conclude that attackers are less fit than non-attackers within groups, while groups with attackers are more fit than groups with non-attackers. Group-level selection must be invoked to explain the example.

      When you explore alternative explanations, you note that an attacker bears an individual cost and gets a share of the group-level benefits. If the share is sufficiently large, then the attacker will increase his fitness compared to not performing the act. But this “What if I do it compared to what if I don’t?” comparison is different than comparing attackers vs. non-attackers within the same group. The biological example hasn’t been changed, but the frame of comparison has.

      Since natural selection is based on relative fitness, knowing that an individual increases its own absolute fitness by an action is not sufficient to know whether the action will evolve. For that we need to make additional assumptions–that the population consists of many groups and individuals with random variation among groups. In that case, the actor will have an effect on itself and the other members of its group will be a random draw from a large population, so any effect on them, positive or negative, will have no effect on global evolutionary change. The correct prediction is that the action will evolve when it increases the absolute fitness of the actor. This is used as a benchmark to define “individual-level selection”. It’s not wrong as an accounting method–but it’s different than defining individual-level selection in terms of relative fitness within groups.

      I have a chapter on equivalence in my book Does Altruism Exist? and Samir Okasha’s book on multilevel selection is another good reference.

  • Ralph Haygood says:

    “historians will look back in wonderment as to how otherwise smart people, who were part of the same scientific community, managed to remain so divided in their own minds about the importance of group selection in human evolution”: I’ve been looking on in wonderment for about 20 years now. I suspect much of the problem is that many of those people aren’t very numerate. Analyzing selection involves a kind of accounting – it’s inescapably quantitative – and the accounting for group selection is more complicated than for individual selection.

    The problem also has a sociological dimension. When I was in graduate school, I heard and read V. C. Wynne-Edwards (and others, but Wynne-Edwards was the favorite whipping boy) repeatedly pilloried for “carelessly” invoking group selection circa 1960. The message was clear: don’t be like that “crank” Wynne-Edwards. That message is oversimplified to begin with, and it easily oversimplifies even further: don’t have anything to do with group selection.

    More broadly, I’ve noticed that many evolutionary biologists seem particularly sensitive to the possibility that someone might accuse them of being “soft headed”. Having entered evolutionary biology from physics, I find the contrast mildly amusing: few physicists worry about such accusations, which probably contributes to their willingness to contemplate some pretty wild ideas.

    • David Sloan Wilson says:

      Dear Ralph–I wholeheartedly agree with you about the sociological dimension of the group selection controversy. I wish it was otherwise, but most scientists-in-training learn to avoid ideas labeled as taboo just like everyone else. In addition, the evolutionary biology’s swing toward individualism in the 1960’s coincided with a more general swing that included economics (Homo economicus), the social sciences (methodological individualism) and everyday life (Margaret Thatcher’s quip that “there is no such thing as society”). I still remember people enthusing about how much evolutionary theory resembled economic theory as if this was an indication of generality, when in fact it was only an indication of a culturally provincial and myopic view!

      On MLS theory being inherently more complex, I agree only part way. I can explain MLS to a general audience in less than a minute by first asking them to imagine playing the game of monopoly and then imagine them playing in a monopoly tournament where the trophy goes to the team that collectively develops the properties the fastest. The audience instantly gets the difference between tying to best other players of the same game and working as a team to best other teams. When considering biological examples, it is not difficult to ask the main questions: 1) What are the social behaviors? 2) What are the groups within the social interactions take place? 3) Which behaviors have the highest relative fitness within groups? 4) Which behaviors are best for the group?

      That said, W.D. Hamilton structured inclusive fitness the way he did because to emulate the decision-making process of an individual, calculating effects on self and others, weighted by a coefficient of resemblance to self. In other words, he made the theory intuitive for people accustomed to thinking only in terms of their own gain! You do have to wean yourself from individualism for MLS to become common-sensical.

      • Helga Vierich says:

        To the extent that phenotypes are modified by their environments, regularities in the environment also contribute to the heritability of behaviors. In turn, collective cultural behavior modifies the effects of natural selection in humans. For example, humans have cultural traditions of building shelters, often associated with contained zones of active combustion, and of covering themselves with flexible material to control individual microclimate. These modify the effects of natural selection by reducing mortality due to cold, predation, and excessive sunlight exposure. The use of fire, the construction of shelters, and the design, making, and wearing of clothing and bedding material are all learned behaviors, and vary in detail from one culture to another in ways consistent with a model of culture as a mode of learned and shared adaptive behavioral inheritance.

        It is universally acknowledged that, in the course of human evolution, there must have been positive selection favoring intelligent minds receptive to learning, retentive of established skills, older fashions, and cumulative information as well as innovation and problem solving. In every culture, there is persistence of variation stemming from a tendency to conserve old traditions and practices, often over a very long time, which exist side-by-side with constant tinkering and creativity. Ideological tension between conservative and innovative social forces is generated by this interface within the cultural cognitive niche. In other words, humans were shaped by culture to be retentive tinkerers.

        Cultural information has degree of fidelity and cumulative variation: by definition, and in fact has recently been described as a kind of “swarm intelligence” or “hive mind”. In each culture there is a common pool of information that all adults share, but beyond that we always see encyclopedias of knowledge and skill that are usually very limited in distribution. For problems requiring highly specialized bodies of knowledge and skills, in every culture, people tend to call in their experts. This is something I found among hunter-gatherers as well as among forest swidden farmers and nomadic pastoralists; it was instantly familiar form my own experience as a child in an industrial state.

        To explain how humans evolved a cognitive niche called culture, we need to explain the development of high variability of minor personality and cognitive phenotypes within each human deme, for it is this variation that make such hive or swarm mind phenomenon (cultures) possible. Selection which serves to increase the frequency of phenotypes that are sensitive to innovation and novelty needed to be balanced by selection enlisting phenotypic traits capable of methodical retention and “re-construction” of information and skills. So, just as in your example of freeloaders vs altruists, how could natural selection achieve this balance but in the context of the group?

        I think that if we look at the variety of skills and talents that we value in on another, we might find a more complete and interesting aspect as well. Possessing a fine singing voice, ability to compose new music, or play musical instruments, ability to produce tasty meals from common ingredients, ability to create comedy, to solve interpersonal disputes, to run fast, to track animals, to make a better mousetrap, to design a better digging tool, a more comfortable garment, to orchestrate a more effective ritual event… all of these and many more individual abilities and talents can attract one person to another. Of course that is only a beginning, as shared values, compatible temperaments, similar backgrounds, and even similar tastes for adventure, also play a role, and, as if that was not enough, it seems people are also attracted to opposites!

        Genetic polymorphisms affecting dopamine such as the DR4 variants , appear to be related to novelty seeking, while other genetic regions have been linked to retentive and hoarding and conservative behavior. In both cases it seems that carriers might be very beneficial to have in a population, even though the behavior of the rare individual, who gets two copies of these variants, might be a bit extreme. There is, furthermore, evidence of many hundred, perhaps even thousands of genes, each with many possible alleles (variants) which influence cognitive function and behavioral variability.

        I note that these polymorphisms in many cases appear to be very old, and may well have played a significant role in developing and expanding the overall cognitive capacity for culture. Clearly we are the descendants of those populations where these polymorphisms occurred. Indeed natural (and sexual) group selection might have conspired to keep adding all kinds of variants and spreading them throughout the human genome. Human variation in temperament and personalities is relatively simple compared to variation in interests and passions. And all this complexity interacts. It could be plotted on a bell curve of ratios of individuality to collectivity – with novelty seeking hipsters and anal-retentive fusspots at downslopes of the distribution.

        In addition, the high sociability, and cooperative nature, of human economic systems, entailed selection pressure for a quality still poorly defined: emotional intelligence. This is linked, not only to qualities for successful interaction with other people and qualities such as impulse control , but also to some of the “dark triad” traits that have been identified in the research on human psychology: narcissistic, manipulative (subclinical psychopath), and Machiavellian tendencies.

        Finally, there is the as yet unknown range of possible genetic entanglements involved in the kind of heightened sensitivity that we regularly see in a about a fifth of humanity – the creative ones, the geniuses, the ones that seem to represent the quicksilver of the human mind , but also the ones who tend to occasionally get irritable with too much noise or other stimulation, as well as the ones who slide into schizophrenia, autism, and obsessive-compulsive disorders.

        Seen thus, the remarkable variety of normal human quirks all appear to be the outcome of a cognitive system finely honed (or perhaps a better term would be jury-rigged) to be a vehicle for replicating, hosting, tweaking, and curating the necessary variation so that every culture could be subject to natural selection in its own right, and could adapt and evolve in response to the necessities of its environment. Whether we prefer to see human culture as a modifier of natural selection working on our genome, or as an integrated assemblage of information evolving, much like the biological genome, and thus similarly subject to natural selection, is perhaps a matter of perspective.

        What remains fixed, no matter what the perspective of the observer, is the clear fact that humans are a profoundly social species, one in which the behavior of adults, individually and collectively, cannot be explained without recourse to inheritance of more than genetic material. Furthermore, our genetic material, our biological nature, cannot be explained without recourse to a model that includes cumulative systems of information passed on via means other than genes. The environment to which the human species was adapted was thus, cultural. It did not matter if an individual baby was born with genetic traits leading to superior running speed, if that child cannot learn to acquire common acceptable behaviors and habits of interaction within its community, it will be unlikely to find a mate and reproduce. Ability to learn culture and language is a fundamental hurdle every neonate must overcome in our species. No wonder new parents tend to anxiously await their baby’s first word, the first smile, and the first signs of inter-subjective understanding!

        Moreover, our methods of communication, language used in story telling, are vital for the enlargement of imagination and for comprehension of other people as being “like” ourselves. We tend to think in metaphors and analogies, both of which extend the imagination and bind it to our theory of mind, so essential for inter-subjectivity that nourishes networks.

        Connections between thousands of individuals over culture areas that in turn spanned vast areas, might seem ambitious, but only from the perspective of outcomes. However, seen from their points of departure – in the eager chatter of friends and relatives, united at various times, over the course of years and lifetimes, – such local networking systems can easily be seen to convey information, and even a few small material things, from one local culture to another, adding up to interconnections spanning great distances.

        Imagine a time before telephones or letters… you might be living in a small river valley, a thousand miles inland, but you might be six connections away from an individual living along the coast. If a monstrous sea creature washes ashore near her, you will eventually hear about it. Word will, literally, spread. Seen from their points of departure – in the eager chatter of new and old friends and relatives, united now and then over the course of years and lifetimes, – such local networking systems can easily convey information, innovations, and small material things, from one local culture to another, adding up to interconnections spanning continents.

        The monstrous sea creature might grow in the telling, but it will reach the ends of the earth before it fades into memory. Seeing the open sea for the first time, a thousand years later, a person originally from your little river valley, is more likely to be aware that there were more than tasty and manageable fishes therein.

        Becoming a species deeply ensnared, for its very survival, in the restless and relentless creation and accumulation of information via technological skills and cooperative sociability, thus imposes a ruthless selection pressure on cognitive systems. To withstand this pressure, it is clear that small, local groups consisting of the shared information of few hundred individuals is inadequate. The larger the number of human minds involved, the wider the social network, the greater becomes the store of knowledge and the higher the probability of cross-fertilization of ideas.

  • Helga Vierich says:

    The interesting thing about your excellent essay on group selection is the fact that like so many biologically trained evolutionary scientists, there still seems to be a tendency to tip-toe carefully around the obvious fact that the elaboration of culture made of the “cognitive niche” a COLLECTIVE cognitive niche. The primary environment shaping human minds and behaviours was and is culture, which is by definition group selection.

    • David Sloan Wilson says:

      Dear Helga–Thanks for your two comments, which I agree with in most respects. So many aspects of culture are communal in their benefits and therefore products of group-level selection. Also, as you say, the distinction between altruism and selfishness doesn’t even scratch the surface of behavioral variation, which will have both genetic and phenotypically plastic components. I’m intrigued by studies of honeybees showing that genetic diversity within hives is important, not just for disease immunity, but for division of labor. Even though every worker is capable of performing all tasks, it is also important for the workers to have innate preferences for tasks. I expect the human case to be much the same.

      I encourage you to write one or more articles for TVOL elaborating on your perspective.

  • ishi crew says:

    I heard on BBC radio last nite a story about how female Bonobos help their male children find mates—-run off competitors.

    I admit while MLS theory may be a better term, i still like the old fashioned term GS. I view models from condensed matter physics—though not exactly analogous to biological ones since they dont have DNA and the process of Darwinian evolution, as good abstract models of GS or MLS theory. (There are some academic papers which take that approach.) You have to transform (add complexity) those models to make them more like biology.

    The well known ‘Edge’ online magazine has all these debates between people like S Pinker , Coyne, Haidt, and others. That shows the psycho-sociological aspect of these debates. (You have the same thing in linguistics—innatists vs empiricists.)

    My area has some informal book clubs—-and the most popular books are by Pinker, other evolutionary psychologists, J Haidt (who i j heard on radio with DSW ), while they do not like books by Boyd and Richerson, DSW, and others. Alot of people do not like to talk about ‘cultural effects’ and these groups tend to be dominated by (probably) straight white males and their (often female) followers. They prefer talking about innate genetic (including cognitive) differences, which exist, but many are ‘markers’ (eg where did you get your PhD if you have one, or what zip code do you live in.) (If you bring up some alternative theories, you will be told to ‘shut up’ and ostracized.)

    Haidt also has a very amicable youtube interview with Jordan Peterson (who seems to mix facts and fantasy together to make a good story, which he sells to make big money). Haidt, Pinker, and Peterson co-miserate about topics like postmodernism, post-structuralism, intersectionality, the lack of rationality and censorship of ‘free speech’ on college campuses. Their critiques are apt—-but they also do not practice what they preach.

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