Evolution for Everyone

Meet Athena Aktipis–evolutionist, mother of two, and salsa dance instructor in her spare time. Perhaps it was the dancer in Athena that caused her to teach multilevel selection by having the students get up and move.

Each student is given a wooden stick with an A (for Altruistic) or S (for Selfish) written on one end. Information on the blackboard tells them that altruists give three fitness units to their partners at a cost of one fitness unit to themselves. Selfish individuals receive without giving. Then they are instructed to move around the room and find a partner at random without revealing their identities. At the count of three, they reveal who they are and write their gains and losses on a 3×5 card. After repeating the process of pair formation and social interaction several times, the students total their score and take their seats for a few minutes of instruction.

I have started to use Athena’s method in my classes and it is wonderful to see how the students come alive when they are allowed to move. Before they were fighting to stay awake in their chairs, but now a party atmosphere develops as they find their partners. Groans and cheers erupt when they present their sticks to each other. Altruists experience the joy of receiving, in addition to giving, when they are paired with another altruist, resulting in a net gain of +2, but they experience the agony of betrayal when paired with a selfish individual, receiving a loss of -1. Selfish individuals score big when paired with an altruist, for a gain of +3, but it’s a drag to encounter another S, resulting in a 0.

Athena’s method enables the students to understand the concepts of within- and between-group selection more vividly than from a dry lecture. Altruism is locally disadvantageous, which I have called “the original problem” throughout the T&R series. The students experience this for themselves when S trounces A in every mixed pair. But altruism is successful at a larger scale, as the students also experience when AA pairs produce a net gain of 4, compared to only 2 for AS pairs and nothing for SS pairs. What evolves in the total population depends upon the net effect of the opposing selection pressures. With random pair formation, within-group selection trumps between-group selection. The average S accumulates more points than the average A and wins the Darwinian contest. A message to the wise: beware of your partner in anonymous social interactions.

Now the exercise is repeated with a single twist. Partners are allowed to stay together by mutual consent. Only students on the rebound from unhappy unions must seek new partners and they can’t break up happy couples. After several rounds of play, most of the altruists are smiling and most of the selfish individuals are looking pretty grim. AA pairs elect to stay together while AS and SS pairs break apart. After several rounds, most of the A‘s have found each other, forcing the S‘s to interact by default. Within-group selection still favors selfishness and between-group selection still favors altruism. Only the balance between levels of selection has changed in the second example, by concentrating individuals into AA and SS pairs and gradually eliminating the AS pairs. In her scientific research, Athena creates theoretical models similar to this version of the exercise, which she calls “walk-away” models.

In a third version of the exercise, each student is given both an A and S stick to present as they see fit and several interactions take place within each pairing. Now the mind games begin, as some students try their luck with the selfish option, typically resulting in retaliation from their partner during the next round of play. No matter how complicated the strategy of employing A and S, however, the basic logic of multilevel selection applies. Selfishness is the unbeatable strategy within each pair; altruists never beat their own partner; they can only lose or draw. It is necessary to increase the scale of comparison to find fitness differences weighing in favor of altruism.

I have created a fourth version of the exercise to illustrate the principle of kin selection, which begins by forming the students into groups of six. Two members of each group are designated as Mom and Dad, who are about to have four children. Mom and Dad are given two sticks each, which might be 2 A‘s, one A and one S, or two S‘s. These are their two chromosomes, since it is necessary to include sexual reproduction to illustrate kin selection. The A allele is assumed to be dominant, so AA and AS genotypes behave altruistically and SS genotypes behave selfishly.

Now Mom and Dad proceed to have four kids by randomly showing one of their sticks to each of their four children. It’s not as much fun as having sex, but it will have to do! In this fashion, each kid obtains their genotype from their parents, just like Mendel’s peas. For example, if Mom is SS and Dad is AS, then all four kids get an S from Mom, while half (on average) get an A from Dad and the other half get a S from Dad. When the kids start interacting with each other, half will behave altruistically (AS) and half will be selfish (SS). The composition of each group of siblings will depend upon the genotypes of their parents in similar fashion.

What is the result of this exercise? When the siblings interact with each other, the basic logic of multilevel selection remains unchanged. Mixed groups are still formed (as in the above example) and selfishness still wins within each mixed group. The new twist that is introduced with kin selection is in the way that the groups are formed. Sibling groups are formed through the funnel of their parents’ genes, which increases the likelihood of altruist-altruist and selfish-selfish pairings and decreases the likelihood of altruist-selfish pairings, even though they still occur. This way of forming groups has the same effect as the second version of the exercise, when individuals could select their own partners. Perhaps this explains why we are so nice to both family and friends. In both cases, altruism evolves because between-group selection trumps within-group selection.

Athena’s teaching method gives students a visceral feel for the generality of multilevel selection. Social interactions almost always take place within groups of individuals that are small compared to the total population. The minimum group size is 2, but everything that my students learned in pairs applies to larger groups. No matter how the groups are formed–at random, on the basis of experience, or through the funnel of genetic relatedness–no matter how flexible the choice of behaviors–altruism is locally disadvantageous and requires higher-level selection to evolve. It doesn’t matter whether you call it group selection, kin selection, reciprocity, game theory, selfish gene theory, or anything else. All evolutionary theories of social behavior include the original problem and solve the problem only by identifying factors that enable between-group selection to overcome within-group selection. As Ed Wilson and I concluded at the end of our review article titled “Rethinking the Theoretical Foundation of Sociobiology”, “Selfishness beats altruism within groups. Altruistic groups beat selfish groups. Everything else is commentary.”

William D. Hamilton, the legendary founder of inclusive fitness theory (dubbed kin selection by John Maynard Smith), required several years and lots of math to reach the same conclusion.

To be continued…


  1. #1 piker
    November 3, 2009

    Wow, those students evolved right before our eyes.

  2. #2 Sam C
    November 3, 2009

    To a man who only has a hammer, everything looks like a nail. It seems that to a group selectionist, all selection looks like multi-level selection.

    Why is this interminable blah labelled “truth and reconciliation”? It’s a genteel and increasingly tedious sneerathon. There’s no attempt at truth, just advertising the same old group selection waffle and incessant assertions of its superiority. As for reconciliation: that is not achieved by damning your opponents with faint praise at best, trying to attack their ignorance at worst. Why the little snark at Bill Hamilton at the end – had he upset you guys? Variant theories that do not originate from True Believers of the Church of Wilsons, such as kin selection, are poo-pooed as “naive” versions of group selection, which, I suspect, betrays a deep failure to appreciate the genetic aspects of selection, and the primacy of real world genetics over mathematical game-playing.

    Once one dumps the plethora of abstractified models in the bin, this argument is really about the formulation of conditional probability distributions (or partial differential equations for the more deterministically minded) and the relative values of their parameters. The group selectionists want to frame the conditionals one way, those who are unimpressed focus on an alternative, perhaps orthogonal, interpretations. And most camps seem to want to include “fitness” in this. But fitness does not exist; it is not a trait, it is not part of a phenotype, it is not part of a genotype, it is an abstract construct. Arguments about fitness easily become silly.

    Contrary to what this post asserts, it does matter whether it’s called (for example) selfish gene theory or not. It is simply idiotic (and naive!) to state otherwise. As I understand it, selfish gene theory proposes that the sole important factor in evolution is that it proceeds by the differential replication of alleles of genes (and other genetic features of course) and that everything can be interpreted in that light, even stuff involving gruops. (I’m prepared to be corrected on that interpretation, I read The Selfish Gene when it came out, and never since!). To paraphrase the statement that you seem so smug about: “Evolution is about the differential replication of genes. Everything else is commentary.”

  3. #3 Guy
    November 3, 2009

    I like the classroom exercises you describe. I have considered doing something similar myself in a way that emphasizes how the individuals (and genes) constituting a group can be irrelevant to the group selection dynamic. I would do this by having individuals put on colored hats to identify their group membership, but allow individuals to change groups and hats. The continuity of the hat-groups, and the group level dynamics, would work continuously even after groups no longer have any of the individuals they started with. By the way,the potential for utterly disconnecting individual and genetic identities from group identities is one way to illustrate how evolution dynamics are not just “about the differential replication of genes”, as asserted in a post by Sam C.

    This may anticipate a direction you plan to take your blog, but I think you are losing credibility in the eyes of some of your audience by so aggressively attacking logical flaws of the evolutionary science community at large. Alternatively, the idea of multilevel selection could be explained as a logical expansion of the traditional viewpoint. It honors the core ideas of the traditional view by respecting their relevance in a larger scope of evolutionary phenomena. Individual level selection is an important aspect of MLS. Traditional Darwinian and neo-Darwinian thinking leads so naturally to MLS thinking that there must be a carrot that would help bring traditionalists along.

    By the way, I think that gene-level selection thinking is utterly wrong-headed, except for the case of meiotic drive. In my view, the evolution of Mendelian segregation achieved the conditions that prevented selection from acting at the level of the gene. Every gene copy has an equal chance of passing into gametes and from there it is the functional performance of gametes, individuals, and groups that matter. Selection at levels above the gene are the unit of selection DOG wagging the tail of genetic variation.

  4. #4 daedalus2u
    November 3, 2009

    The ‘walk-away’ model explains biofilms quite well. It also explains the planktonic-sessile transitions in both directions. It explains quorum sensing to trigger those transitions in both directions. Most natural biofilms are quite heterogeneous, with many different organisms in them. Group-level selection of biofilm-supporting genes and control systems fits very well with the data. Virulence is triggered by quorum sensing and is pretty much only a group activity.

    Control of surface infections via interference with quorum sensing is the major mechanism that eukaryotes use to prevent biofilm formation on their surfaces. The bacteria I am working with, ammonia oxidizing bacteria are a major factor in that for many eukaryotes. High NO levels disrupt most biofilms. It is high NO from surface biofilms of ammonia oxidizing bacteria that suppress heterotrophic biofilms by switching them from a sessile phenotype to a planktonic phenotype.

  5. #5 David Sloan Wilson
    November 4, 2009

    Sam C begins by criticizing multilevel selection theory for trying to account for all cases of natural selection and ends by describing selfish gene theory as accounting for all cases of natural selection. That makes them BOTH hammers for pounding all nails, which is a virtue for a theory that is trying to be general. What Sam C seems to miss is that the group selection controversy is not about coming up with a general theoretical framework. It’s about evaluating a factual claim concerning the likelihood of traits evolving in the total population when they are locally disadvantageous. The received wisdom is that such traits seldom evolve, I’m here to say that they frequently evolve, and I can win the argument using either multilevel selection theory or selfish gene theory. I am exposing the fallacy of the argument “selfish gene theory explains everything that evolves by natural selection, therefore group selection hardly ever happens.” This argument sounds absurd when stated as such and when appropriate background is provided, but any scholarly history of evolutionary theory will show how pervasive it was and still is.

    The existence of more than one general theoretical framework (such as selfish gene theory, multilevel selection theory, and inclusive fitness theory), their equivalence, and why one might count as better than the other is a hot topic in the academic literature. To access this literature, use key words such as “equivalence” and “pluralism”. Regardless of how the “my general framework is better than yours” debate turns out, everyone needs to realize that it’s a different debate than evaluating the aforementioned factual claim.

    Along with Guy, I don’t quite understand the insistence by some commentators that evolution must involve genetic replicators, when Dawkins himself saw the need for a meme concept comparable to the gene concept. Once again, memes by themselves say nothing about the likelihood of cultural group selection, since memes can spread either on the strength of a local advantage or despite being selectively disadvantageous within groups.

    I become impatient when I read statements such as “fitness does not exist”. Explain to me how any framework for thinking about natural selection can get going without a concept of fitness. All concepts are abstractions. What’s the alternative? When we do think about fitness, remember that it is indeed not a trait–it is a relationship between a trait (such as the shape of a bird beak) and the environment.

    I’m amused by complaints that this series is going on and on and on, when its final length will be approximately that of a single major review article. This might be the ADD generation, but anyone who wants to play the science game must be willing to scrutinize concepts and data in detail. Believe me, what I am relating is compact compared to the academic literature.

    I appreciate Guy’s helpful suggestion that I might be losing credibility “by so aggressively attacking logical flaws of the evolutionary science community at large. Alternatively, the idea of multilevel selection could be explained as a logical expansion of the traditional viewpoint.” Surely, if there IS a logical flaw, then it is the business of science to identify it and stamp it out. If it is a pervasive logical flaw, then stamping it out becomes even more important. If it is a pervasive logical flaw that has persisted for decades, then the scientific process is not working as it should and needs to be fixed. Fixing a broken scientific process is different than science as usual. Besides, science is a contact sport and we can still good naturedly go out for a beer after we try to throw each other to the mat.

    Daedalus2u is functioning in normal scientific mode when he briefly describes biofilms from a multilevel evolutionary perspective. Microbes that make biofilms possess many traits that count as public goods produced at private expense. The clustering that enables such traits to evolve is accomplished in part by genealogical relatedness (kin selection, if you like), but also by assortative interactions similar to the walkaway models. Multilevel selection in microbes is a very hot topic, especially because the population structure can be so easily manipulated, evolution can take place over thousands of generations, the generations can be frozen to provide a living fossil record that can be brought back to life, the genetic changes can be studied in great mechanistic detail, and so on. Names include Greg Velicer, Paul Rainey, Kevin Foster, David Queller and Joan Strassman, Benjamin Kerr, and my own colleague at Binghamton University, Alex Rickard, who studies the multi-species biofilm community that makes dental plaque. No one will be happier than me when everyone operates in normal scientific mode for the subject of multilevel selection.

  6. #6 piker
    November 4, 2009

    Dr. Wilson,
    If you equate microbial evolution with human on the level of producing public goods at private expense, you are again observing the similarity of strategies in all living things, REGARDLESS of their group environments or dynamics. The microbial strategies ARE a part of their physiological makeup, and when the environment changes, the microbes change genetically so that their strategies will continue to be effective. In the case of humans, as you have conceded, the basic strategies adapt to the change in the group cultures, but WITHOUT the necessity for physiological change in the process.

    In effect we have evolved from having the need to make physical changes as an adaptive response to the need to make cultural changes as an adaptive response. You note the similarities in the mechanisms but seem to have no understanding of the extent of the differences.

    You are either deluding yourself or attempting to delude us (or both) when you persist with your altruism/selfishness dichotomy as the key to this understanding. This is not the “scientific mode” that you advise everyone to accept as the normal. This involves a fundamental mistake in your hypothesis (if only one of many) that you refuse to acknowledge, except to weasel around with the semantics and blur the definitional differences between natural selection and cultural selection.

    If this is, to quote from your own admonishment, “a pervasive logical flaw, then stamping it out becomes even more important.” Except that it’s your pervasive flaw in particular that you are refusing to put the stamp on.

    You have become hoist on your own intransigent petard.

  7. #7 ChrisJSF
    November 4, 2009

    I’m no biologist but I do know full well that “You have become hoist on your own intransigent petard” is not in keeping with English grammar.

    And do you always use unnecessarily puffy language when flaming? If you’re confident about your criticism you shouldn’t need to misuse your word-of-the-day calendar to make it convincing. You must be halfway through March on that thing.

  8. #8 piker
    November 4, 2009

    PHRASES: hoist with (or by) one’s own petard have one’s plans to cause trouble for others backfire on one. [ORIGIN: from Shakespeare’s Hamlet ( iii. iv. 207); hoist is in the sense [lifted and removed,] past participle of dialect hoise (see hoist ).]
    ORIGIN mid 16th cent.: from French pétard, from péter ‘break wind.’

    Or: hoist with your own petard also hoist on your own petard
    to be harmed by something that was intended by you to harm someone else The most enjoyable moment in any action film occurs when the villain is hoist with his own petard.
    Etymology: based on the literal meaning of hoist by your own petard (blown into the air by your own explosive device), an expression made popular in Shakespeare’s play, “Hamletâ€

    the regime remained intransigent in its opposition to wider participation in the political process: uncompromising, inflexible, unbending, unyielding, diehard, unshakable, unwavering, resolute, rigid, unaccommodating, uncooperative, stubborn, obstinate, obdurate, pigheaded, single-minded, iron-willed, stiff-necked. ANTONYMS compliant.

    I accept that you’re no biologist or you’d have focused on any deficiencies in the criticism rather than in the grammar. Demonstrating that you aren’t much of a grammarian either.

    Not much of anything if this the best you can do by way of commentary.

  9. #9 daedalus2u
    November 4, 2009

    piker, individual bacteria switch from a planktonic phenotype to a sessile phenotype and start making sticky-stuff to form the biofilm. No genetic change is needed, only the detection of the particular quorum sensing compounds that that particular strain of bacteria uses.

    Those individual bacteria make a public good (biofilm support substrate) at private expense (by exporting carbohydrate they could otherwise use internally). This change happens within the life span of a single bacteria, no genetic change is needed or even happens. Whether the change is hard-wired controlled by genetics, or controlled via the “software” of culture is not determinable from “outside” the organism. Treating them differently because of non-determinable factors is inappropriate.

    Your denigration of bacterial communication and interactions as “genetic” and human interactions as “cultural” is due to anthropomorphic thinking; or rather the rejection of anthropomorphic models for bacteria while embracing them for humans. It is just as valid to say that bacteria have a “culture” which they communicate via quorum sensing compounds as to say that humans have a culture which they communicate via language. The “details” of the two languages are irrelevant to the model of the generation of a public good at private expense.

    This is precisely why I don’t like anthropomorphic metaphors. They carry a baggage of inference that can be quite misleading. “Selfish” and “altruistic” are problematic states to apply to organisms that are not self-aware and able to think and plan. So far as we know, bacteria are not self-aware and are unable to think and plan, so attributing states to them that require those things are problematic.

    The human capacity for both behaviors is mediated genetically. So is the bacterial capacity for biofilm generation. The switching between the two states is mediated through quorum sensing in bacteria and through many different things in humans, including language. Is there some fundamental difference between these two? If so, what is it?

  10. #10 bob koepp
    November 4, 2009

    Well, I do know that a petard isn’t the sort of thing that can be intransigent…

  11. #11 NewEnglandBob
    November 4, 2009

    ‘break wind.’ seems to be a common theme here.

  12. #12 piker
    November 4, 2009

    Actually bacteria and the like DO have a culture, but if you are denying that they change their physiology as an adaptive process, you’re simply wrong. I don’t denigrate the nature of bacterial communication at all by saying this. The quorum sensing procedures are a remarkable demonstration of how bacteria can calculate and learn from results and evolve accordingly.
    Humans can calculate and learn, but we don’t evolve in the physical sense anywhere near as accordingly – precisely because bacteria and the like have done the bulk of that job for us. We will continue to evolve, but not with any such immediate correlation between our tactics and our physiology.

    And let me quote your own comment as confirmative here: “This is precisely why I don’t like anthropomorphic metaphors. They carry a baggage of inference that can be quite misleading. “Selfish” and “altruistic” are problematic states to apply to organisms that are not self-aware and able to think and plan. So far as we know, bacteria are not self-aware and are unable to think and plan, so attributing states to them that require those things are problematic.”

    Although the quorum sensing to me shows that bacteria do have a rudimentary mechanism akin to thinking and planning, because quorum sensing wouldn’t work without some ability to expect or anticipate the steps taken in that procedure.

    Underlying the disagreements between Dawkins and Wilson may also be their feelings about whether humans evolve at all in ways that correlate with their behavioral experience. Wilson would seem to expect that we do (as do I) while Dawkins seems sure that we don’t. Otherwise he wouldn’t have needed that cockamamy meme theory to explain the innate cultural intelligence of infants, as one example. But I digress.

  13. #13 piker
    November 4, 2009

    bob koepp writes: “Well, I do know that a petard isn’t the sort of thing that can be intransigent…”

    Just like you thought you knew that yin and yang must represent “monism and pluralism” without reference to the balance between them.

    But I suppose sniping from the peanut gallery beats commenting on the merits of an argument from the same distance.

  14. #14 daedalus2u
    November 4, 2009

    piker, no. You are using sloppy terminology and/or sloppy reasoning. Bacteria communicating with quorum sensing and changing their physiology accordingly is not “evolving”. There are no changes in frequency of genetic material.

    Individual organisms changing their phenotype without genetic changes is not evolution. The “calculation” and the “thinking and planning” that bacteria do in response to quorum sensing is akin to the “calculation” and the “thinking and planning” that a human does as that individual grew from infant to child. It is a change in phenotype in response to an environmental cue. Not change due to “culture”, or “calculation”, except using contrived meanings of the terms.

    Define what you mean by “culture” and “calculation” and I might agree with you. As you are using the terms now they are inconsistent.

  15. #15 piker
    November 5, 2009

    daedalus2u, I did not say or intend to imply that bacteria change their physiology according to quorum sensing. Quorum sensing is a strategic tactic, used primarily for predatory purposes, not one that requires adaptation to a new group, culture or environment. (Tactics may well have evolved in conjunction with a physiological change in genetic material, but I don’t know if that had to be the case here or not.)
    And I’m not talking about related or competitive life forms such as parasites whose tactics involve physiological changes that don’t amount to evolutionary changes.
    Defining what I mean by culture is the milieu in which bacteria teach each other certain of the quorum sensing procedures, most of which are otherwise instinctive – somewhat like the more advanced animal cultures where young animals are taught to hunt, how and where to hide, etc.
    You referred to the thinking and planning done by a growing child, but most children would not survive without learning the lessons that can only be taught by other members of their group – which is essentially the purpose and function of culture. And our children are programmed to quickly adapt to our human culture. (Evo psych people think so, in any case. – if probably the only part of their theories they got right.)
    And the cultural learning process didn’t start with humans – in my view, if not of others, it started with the first formation of living individuals into cooperative groups and was in effect the evolutionary glue that kept them together.
    Apparently when you don’t agree, you attribute that to the other party’s sloppy reasoning, but there are certain things we are all ignorant off that aren’t attributable to poor reasoning, and this concept may be one. As to calculation, I shouldn’t have to point out that all life forms make fork in the road choices, such as between the road to pleasure and the one to pain, for example – arguably the first rudiments of calculation.

  16. #16 daedalus2u
    November 5, 2009

    piker, bacteria do change their physiology according to quorum sensing. Quorum sensing triggers the phenotype change from planktonic to sessile. Bacteria do not change their genetics (i.e. their genomic DNA) according to quorum sensing, but which DNA gets expressed certainly does change, that is what causes the phenotype change and the change in physiology.

    The bacteria I am working with, ammonia oxidizing bacteria do form biofilms but they are incapable of attacking or digesting, or even utilizing the digested components of other organisms. Forming a biofilm is strictly a response to the environment. When the environment is good, so there is plenty of substrate (ammonia), they generate a lot of NO, and when that reaches a certain level it triggers biofilm formation so that the bacteria hang around in the good environment that they found.

    If biofilms are produced by bacteria which are not and can’t be pathogens, then some aspects of biofilm formation are not associated with pathogenicity.

    If you consider the phenotype changes by bacteria to be “thinking and planning”, then a fetus in utero is doing a whole lot of “thinking and planning” to control the proliferation, differentiation, and epigenetic programming of all the cells that are going on. That is not what most people mean when they use the term “thinking and planning”.

    Thinking and planning is (to most people) limited to organisms with a nervous system. I am not a specialist in evolution, so if “thinking and planning” is a term used by people who are specialists to mean the kinds of things that bacteria do in response to their environment, that is something I consider unfortunate and yet another mess that needs to be cleaned up.

    Could you give me a precise definition of what you mean by “thinking and planning” such that it applies to both bacteria and children?

  17. #17 piker
    November 5, 2009

    Quorum sensing can trigger physiological change, if that’s what you mean, and can also trigger an evolutionary change. It’s an adaptive function that, as with almost all such functions, can serve more than one purpose. I don’t pretend to know them all, and if you’re learning what they are with your particular strain, that’s all to the good.

    There is no precise definition of thinking and planning that includes the nature of all the functions that the process serves, can serve, has served, or will serve in the future. You may think it unfortunate, but nervous system or no, all life forms calculate (or compute, as some prefer to say), and all form ever changing expectations as a result, and from environmental feedback a form of planning for eventualities arises, and strategies form accordingly, and instinctive behaviors develop accordingly, which are in and of themselves expectations based on what eventually becomes the genotypic game plan.
    And round and round and up and away we all go in different directions. Sorry, but that’s about as precise as I can take it.

  18. #18 CynicView
    November 6, 2009

    By that definition I can say that grains of sand can think and plan for themselves when I pour them into a heap which becomes a mound.

  19. #19 piker
    November 6, 2009

    You could say it, but I expect you would be wrong. Sounds like you believe in the old “water runs down hill” natural selection analogy. But to the best of my knowledge, only homeopaths have found ways to infuse water with expectations.

  20. #20 piker
    November 6, 2009

    But I did hear once of an hourglass that was planning to turn itself over.

  21. #21 Vlad
    December 27, 2009

    It seems to me that the argument for group selection you’re presenting in this post is quite wrong for the following reason: In the second and third installment of the experiment, when partners are allowed to stay together by mutual consent, you are creating the conditions for being individually beneficial to be an altruist. In other words, in these cases it is no longer the case that “altruism is locally disadvantageous” – you have just framed the experiment in such a way that altruism has become locally advantageous. In the third case, when given a choice between A and S, people act altruistically out of selfishness, i.e. because they anticipate the negative effects upon themselves. There’s no group selection here – what you have here is an emergent phenomenon a la Adam Smith’s “invisible hand”.

    This is a key observation if you want to understand cooperative behavior in human societies – such behavior happens only when there are costs attached to becoming a defector. If your group selection argument were correct we could have had cooperation even in the absence of individual costs for defecting.

    So, you have demonstrated that altruism is locally disadvantageous in the first case, but then you have uncritically *assumed* that it remains locally disadvantageous when you alter the conditions of the experiment in the next cases – this is your error – the assumption you made was wrong.

  22. #22 justin tv
    December 30, 2009

    truth is not always the truth.. !

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