On the kindness of strangers: why are humans so nice?

In the next week or so I'll publish a piece describing a tiny act of altruism I performed for someone I'd never met before—and did not expect to meet again.  This happens to us all the time.  The fact is that people are nicer than they should be—at least according to the dictates of evolution.  When you meet someone only a single time, and that person is nice to you, you tend to be nice to them back. This is a frequent observation in laboratory studies of human behavior. 

As I said, that behavior contradicts what we’d expect evolution to produce.  If you have a one-shot encounter with someone, and that person is nice to you, the best evolutionary strategy would be to defect—to not return the benefit.  Since you won’t meet the person again, you have nothing to lose by not reciprocating, and you don't incur the cost of doing something nice (i.e., sacrificing something).  But people in games—and in life—tend to reciprocate in these situations, even when they’re sure that they’ll never meet that person again.  Why do we do this? Why, for example, do we leave big tips even in a restaurant we know we’ll never visit again?

There are two explanations for  such one-shot generosity.  One is cultural: we have simply reasoned our way into extending the generosity and help we have evolved to bestow on our kin and groupmates to other people we don’t even know.  This is the thesis of Peter Singer in The Expanding Circle. He suggests that rationality tells each of us that we hold no special moral status over the rest of humanity, and so we should help others, even at some cost to ourselves, when we don’t know them.  It’s the Golden Rule, but derived through secular reason.

Another explanation is that human generosity in one-shot situations is simply a byproduct of instincts that have evolved for other, more adaptive, reasons. That is the thesis of a new paper in the Proceedings of the National Academy of Sciences by Andrew Delton, Max Krasnow, Leda Cosmides, and John Tooby.  What they show though evolutionary modeling is that humans can evolve to be generous to strangers in “one-shot” situation because they never really know whether a one-shot situation could actually be the beginning of multiple encounters with that same person, encounters in which you can each reciprocate, enhancing your mutual fitness in a big way.

It turns out that in many situations, the small price you pay in being nice to a person on an initial encounter is more than compensated for by the greater benefits you’ll get if, by being nice initially, you establish a reciprocal and mutually beneficial relationship that pays off in subsequent encounters.  (If you defect on the first encounter, that person won’t be inclined to be nice to you in the future.) And since one-off meetings might have been relatively rare during most of human evolution, when we lived in small groups, we might have evolved the tendency to be nice even when we meet somebody for the first time—explaining at least part of our current generosity.

The paper of Delton et al. involves making evolutionary simulations of behavior that include many pairs of people interacting in either one-shot or multiple situations, with each person deciding whether or not to be generous or to defect. The payoffs to each person constitute his evolutionary fitness, and determines the frequency with which his behavior is seen in the next generation (defecting and generosity are assumed to be genetic traits). They show that under many situations individuals will evolve to reciprocate generosity to another person, even when they think they’ll never see him again.  This is based on two assumptions:

  1. The small cost you incur by being generous to someone else in a one-shot situation can be more than compensated for by the larger benefits of a reciprocal and mutually beneficial relationship that forms if you happen to meet that individual again.
  2. Critically, over most of human evolution we didn’t know for sure whether a one-shot encounter might turn into a multiple-shot relationship.  As Delton et al. note:

Using agent-based simulations, we show that a propensity to make contributions in one-shot games (even those without reputational consequences) evolves as a consequence of including in the architecture an overlooked computational step necessary for guiding cooperative decisions: the discrimination of one-shot from repeated interactions.

Imperfect discrimination is the biologically realistic case because real computational systems, such as human minds, cannot know with certainty whether an interaction is one-shot at the time the decision about cooperating must be made. Indeed, given the stochastic nature of the world, it might be correct to say that, at the time of the interaction, the interaction is not determinately either one-shot or repeated.

The authors simulated 500 pairs of individuals who interacted under a variety of situations (one-shot, repeated encounters, different payoffs, etc.), leaving descendants based on the fitnesses realized from their interactions. This evolutionary game extended over 10,000 generations.  They also made two types of models.

Model 1. Cognitive component fixed, motivational component allowed to evolve.  That is, the actor’s belief that an interaction was either one-shot or repeated was a fixed and unchanging value, and what could evolve was the probability of cooperating in a given interaction.

Model 2. Motivational component fixed, cognitive component allowed to evolve.  That is, actors would never cooperate if they thought an interaction was one-shot, and would always cooperate if they thought an interaction would be repeated—these behaviors were fixed and not allowed to evolve.  What was allowed to evolve was the weight of evidence required to convince an actor whether an interaction was likely to be one-shot or repeated.

The results were pretty much the same in both cases: if interactions between a given pair were frequent enough—somewhere between two and five encounters—the motivational component would evolve in the first case: individuals in populations would become more likely to cooperate even if they thought an interaction was a one-shot deal.

Likewise, under the same frequency of repeated interactions, the cognitive component evolved in case 2: as the authors note, Cognitive architectures that are highly resistant to concluding that interactions are one-shot are favored by selection over architectures that are cognitively more accurate.”  In other words, people’s minds evolved to deceive themselves about the reality of interactions, for that type of self-deception yields a higher long-term payoff than would more accurate assessments.

The big conclusion, then, is that we can evolve to be cooperative with someone even when we think we’ll meet them only once, for we’re never certain that it’s going to be just a single meeting, and we’d best be nice in case it isn’t.  It’s a sort of Pascal’s wager on interactions.  As the authors put it:

In short, the conditions that promote the evolution of reciprocity—numerous repeat interactions and high-benefit exchanges—tend to promote one-shot generosity as well. Consequently, one-shot generosity should commonly coevolve with reciprocity. This statement is not a claim that direct reciprocity is the only force shaping human cooperation—only that if reciprocity is selected for (as it obviously was in humans), its existence casts a halo of generosity across a broad variety of circumstances.

Note that this paper explains one-shot generosity in modern societies as the result of evolution that occurred in the past, over millions of years when we lived in small groups.  The situation we live in today, when we can be absolutely certain that we’ll never meet someone again (as when we’re travelling), has not been in place long enough to alter our evolved behaviors.

The authors also note that one-shot generosity is even more likely to evolve if other people observe your behavior, for such observations can give you a reputation as either a cheater or a generous person—a reputation that can spread and affect your future interactions with a lot of other people.

It has not escaped my notice, though the authors don’t mention this, that a similar mechanism could generate an initial “altruistic” act when you meet a stranger in a presumed one-shot interaction.  The price you might pay if the other person doesn’t reciprocate might be more than compensated by that person’s reciprocation, which could then trigger a beneficial longer-term relationship.

All of us, I bet, have both performed and been the recipient of such altruistic acts.  This morning I went to the Finland Station, where the locomotive on which Lenin entered Russia during the revolution was reputed to be housed.  When I asked around about it, nobody spoke English, and everyone was baffled at my inquiry, even when I drew a locomotive with a little Lenin guy on it.  But a student who spoke broken English came up to me and, after a long and difficult conversation, he realized what I wanted. He then took me around the station to speak to various officials so I could be allowed onto the train platform, where the locomotive indeed resided.  They finally let me out there, and I saw and photographed the locomotive (pictures will come soon).  What a nice person he was, and of course he got nothing for his actions save my fervent thanks and a handshake.  Perhaps those acts of kindness, too, reside partly in our genes. (Now this isn’t really true altruism, in the sense that the donor gets nothing back, but it’s “altruism” that may have evolved in our ancestors when you really did expect, on average, to benefit from the behavior.)

This isn’t really my area of expertise, but I think the paper is an important one. It shows that under the right conditions a previously inexplicable type of human behavior—at least inexplicable from an evolutionary standpoint—can evolve as an inevitable byproduct of human interactions.

There are two potential problems with this paper.  The first, and less serious, is that we realize one-shot generosity as an evolutionary byproduct only if interactions between pairs of individuals are frequent: five is a good estimate.  That’s not so unrealistic, though, since for millions of years our ancestors probably lived in smallish groups. Over most of our evolutionary history, repeated interactions with others were probably the norm.

The other problem is genetic: the authors’ model is asexual, that is, each behavior or cognition is simply transmitted as a whole from one generation to the next.  This simplification makes the model tractable, but is rather unrealistic.  Behaviors are not all-or-none traits produced by single genes, but are usually based on several to many genes that can recombine with the genes of mating partners, producing intermediate behaviors.  It’s not clear whether a more realistic genetic model would produce results similar to that of Delton et al. I suspect it would, but that’s only a guess.

Nevertheless, and though I haven’t been a huge booster of the Toobey/Cosmides brand of evolutionary psychology, I see this as a pretty important paper.  It explains, in a simple and comprehensible way, how a puzzling human behavior might evolve.  Of course, as the authors note above, reciprocity isn’t the only force shaping human generosity, and cultural evolution remains as an alternative or supplementary explanation.

But I still leave larger tips in bars and restaurants when I know I’ll be going back. That’s simply me overcoming the tyranny of my unselfish genes.

h/t: Alex Lickerman


Delton, A. W., M. M. Krasnow, L. Cosmides, and J. Tooby. 2011. Evolution of direct reciprocity under uncertainty can explain human generosity in one-shot encounters. Proc. Nat. Acad. Sci. USA (early edition): doi:10.1073/pnas.1102131108


  1. Jim Thomerson
    Posted July 31, 2011 at 10:58 pm | Permalink

    I’ve thought about this a little. Perhaps it is a matter of wishing to to live in a society were one time nice things happen to me, and doing my part to make society work that way. I have had several nice things done for me by strangers, on a one time basis. So it seems that is the way I am supposed to act as well.

  2. Charles Sullivan
    Posted July 31, 2011 at 11:01 pm | Permalink

    I wonder if this model can explain donating money to charities (Haiti and Japan earthquakes, etc), when it’s clear that reciprocating is not possible, and when one doesn’t brag that one donated.

    I prefer the Singer model.

  3. MadScientist
    Posted July 31, 2011 at 11:14 pm | Permalink

    The models are unrealistic? Of course they are! People seem to have too much faith in models and forget that they are nothing like reality, but a good model can make observable predictions. As for being nice in a “one-shot” situation “… contradicts what we’d expect evolution to produce”, I’d argue that you’re expecting the wrong thing of evolution because you’re looking at an individual and saying that selfish behavior of that individual is a good thing for evolution and no other behavior can be allowed – clearly a flawed model.

    At any rate the model described here reminds me of many economic models. They are far more likely to be telling you what you want to hear – the real challenge is to test the model.

  4. Charles Sullivan
    Posted July 31, 2011 at 11:19 pm | Permalink

    Relevant discussion here between Singer and Dawkins. Begins at 14:40 and end at about 19:00.

    • Notagod
      Posted August 1, 2011 at 10:00 am | Permalink

      Thanks for the link with the relevant part demarcated. The argument from Singer seems well reasoned to me.

  5. Posted July 31, 2011 at 11:32 pm | Permalink

    Tit-for-tat doesn’t HAVE to be ONLY about meeting again or hoping a good deed will be gossiped about…

    I have the common irrational belief that “what goes around comes around” when doing good or evil. I also enjoy performing good even when I will be the only one to know about it. In fact it feels ‘nobler’ to be utterly unrecognised ~ no other living thing conscience of my actions.

    There’s a problem now because I’ve revealed it (a little) so what does that say about my motives ? However I find that this (almost) Buddhist Karma belief is a common thread in the people I know ~ none of whom are Buddhists.

    What can we know of motive ? I think we all have a belief in this Karma thing hard-wired in our religion module. The same module that makes me think I’m simultaneously watching myself from both inside & out and *others* are watching too.

    • Posted July 31, 2011 at 11:42 pm | Permalink

      I hear voices. Even now I hear them. The little voices, all the time, telling me what to do. 🙂

    • Posted August 1, 2011 at 12:15 pm | Permalink

      couldn’t it just be that we have learned as humans that attending to others’ needs is typically beneficial both for ourselves and the survival of society? in order for my genes to survive, society has to survive, so i do what’s good for society.

  6. Posted August 1, 2011 at 12:31 am | Permalink

    I suppose there’s no reason that our evolved reactions to other people would “know” that we’re unlikely to see that person again.

    Also, how much of our niceness is simply learned? As children we’re taught how to behave around other people, and if we behave in a way of which our community approves, we get rewarded. Who doesn’t enjoy the approval of others?

    • Posted August 1, 2011 at 3:26 am | Permalink

      OK, I was going to cite Colin Turnbull’s contrasting studies of the “forest people” (the Mbuti) and the “mountain people” (the Ik) to illustrate how different cultures can have very different standards of niceness. However, I just read that his highly negative portrayal of the Ik has been strongly disputed.

  7. Posted August 1, 2011 at 12:47 am | Permalink

    It’s pretty obvious really. It’s only been during the past few thousand years that we have started to live in communities large enough for us to have one-off encounters on a regular basis.

    Most of the time before that would we not have met the same people repeatedly from within our small clans and therefore every act of altruism would benefit the clan and therefore indirectly benefit the individual?

    If I am not mistaken then a few thousand years probably just hasn’t been long enough to evolve out such traits, especially seeing as nobody dies before reproductive age as a consequence of the adjusted behaviour.

    • cyan
      Posted August 1, 2011 at 5:08 am | Permalink

      I think this, too, and even though the modeling used by the authors of this new paper is not a perfect model, it supports this view.

    • Posted August 1, 2011 at 12:19 pm | Permalink

      that’s a good point, too. i’d even extend it to much less than a few thousands years. the vast majority of human communities are stationary if they can be. (i just went back to visit a little village in germany where i used to spend quite a bit of time from 1960-1966. it was absolutely extraordinary to see how little had changed)

  8. Mike
    Posted August 1, 2011 at 12:59 am | Permalink

    I’ve been living in France for a year now and I’ve had a few discussions with locals and expats over the French way of doing business. In many situations it’s very hard to get the sort of professional caring response that you might be used to elsewhere. A local defended this as a matter of me needing to spend a long time building a relationship with the service giver first.

    It’s not clear how you do this when your first encounters with the service giver have them “defecting” so I’m less inclined to build on the relationship. Similarly many of the public-service encounters are set up with an “expectation of failure” on your first 1-3 visits.

    Would love to read any anthropological studies of such commercial/administrative cultures.

    • Posted August 1, 2011 at 4:10 am | Permalink

      There is an excellent book that might be what you are looking for. It is a bit old (1993) now, but fascinating none the less. It is called “The Seven Cultures of Capitalism” by Charles Hampden-Turner and Fons Trompenaars. It is a book about the value systems for creating wealth in the United States, Britain, Japan, Germany, France, Sweden, and The Netherlands. It is fascinating as, even though all of the countries listed are capitalist, they way that capitalism is carried out is coloured by their social make up.

      • Mike
        Posted August 1, 2011 at 9:26 am | Permalink

        Thank you for that – I’ll look into it.

        What’s additionally remarkable to me is that failures at the granularity of individual encounters do not necessarily undermine the entire system. I’ve spent time in the systems of France, United States and Australia, and there’s a world of differences between their approaches.

    • Posted August 1, 2011 at 3:48 pm | Permalink

      Anecdotally, I’m at a recording session in Indiana, where performers from southern California, British Columbia, and Philadelphia have been brought together — they all remark on how everyone in the Midwest is polite and helpful. Those include restaurant, hotel, and church staff — all are almost certainly one-off encounters.

      I suspect that this kind of altruism is strongly cultural (learned). Imagine the difference between the manners of a typical driver from Boston and, say Madison. They are of the same species, right? But evidently they are from different cultures.

      • Diane G.
        Posted August 4, 2011 at 12:46 am | Permalink

        Boston drivers may, in fact, be a different species…

  9. Harbo
    Posted August 1, 2011 at 1:01 am | Permalink

    Is altruism just intelligent selfishness?

  10. Draken
    Posted August 1, 2011 at 1:40 am | Permalink

    No no, you’ve got it all wrong. We’re kind to each other because a book written by desert nomads in the iron age under direct supervision of the Supreme Being tells us to, or else!. Without this guidance we would be stabbing each other in the back right after our first encounter.

  11. qqq8
    Posted August 1, 2011 at 1:54 am | Permalink

    err. you don’t know if you’re going to see that person again, and you don’t know what kind of tribe that person belongs to, or if you will meet other members of that tribe which might later have heard of your alturism and do good busniess with you or spare your life if they happen to be a warrior tribe when they attack yur tribe.

    id say not being nice back to some stranger is once of the worst survival tactics you can do, since you know so little about the person and where they come from.

  12. Posted August 1, 2011 at 2:35 am | Permalink

    My question is, why does evolution necessarily select against random acts of kindness?

    Remember, our genetic roots come from a, basically, nomadic lifestyle.

    When roaming across a desert looking for shelter, food and water, if you get a reputation for being unhelpful to others you come across, then others may not be so helpful to you in return.

    Nomadic tribes are not entirely alone, selfishly looking for places to shelter. The various tribes tend to bump into each other and know of each other’s existence, how each other are faring and so on.

    • Posted August 1, 2011 at 3:22 am | Permalink

      “…our genetic roots come from a, basically, nomadic lifestyle” it does ? Tell me more please.

      • Posted August 1, 2011 at 3:59 am | Permalink

        Rosa Rubicondior writes far more eloguently than I ever could on the subject: http://rosarubicondior.blogspot.com/2010/07/evolution-of-god-hypothesis.html

        Various science fiction writers have also hypothesised similar scenarios.

        • Posted August 1, 2011 at 4:27 am | Permalink

          Thanks for that Stooshie. I’ve taken a look & “nomadic lifestyle” seems to be irrelevant since the theory also covers agricultural societies. I read it as being about the Alpha male dominated small clan & the effect of increasing the clan size.

          • Posted August 1, 2011 at 4:39 am | Permalink

            Sorry, you are right, not entirely relevant, but she uses our long term history as a guide to why evolution might lead to unexpected behaviours.

            My main point was that evolution doesn’t necessarily lead to greed and selfishness and that a sense of “community” (whatever that entails) and altruism could be an almost inevitable part of the evolutionary process.

    • Torbjörn Larsson, OM
      Posted August 1, 2011 at 5:50 am | Permalink

      It is an easy reach, I initially did the same.

      But wouldn’t that be group selection instead of inclusive fitness though?* If so, Coyne may have some problems with the feasibility of that.

      * I assume the paper studied pairs (“dyadic reciprocity”) for good reason.

    • MadScientist
      Posted August 1, 2011 at 10:59 am | Permalink

      In this cited instance I can’t imagine how it could because it does not sacrifice the propagation of genes – in fact in situations it can encourage the propagation of the genes of a species.

    • Dan L.
      Posted August 1, 2011 at 2:41 pm | Permalink

      I think the idea is that for an act to be considered altruistic it must constitute some loss, however insignificant, for the altruist. Essentially by definition, an altruistic act hurts the altruist.

      So the only way to make altruism a good evolutionary strategy is to ensure that the benefit of the altruistic act outweighs the cost. Often, altruistic acts are low cost/high reward — even simply establishing a reputation as an altruist can have greater benefits than the cost, as you point out with the nomad example.

      But I don’t think the nomad example is a good one for the evolution of altruism. Largely modern humans were living in social groups for more than 200,000 years before animals were domesticated (which is a necessary precondition for nomadic lifestyles). By contrast, there have only been about 10,000 years since the domestication of animals, and only a very small proportion of all human beings who were ever born have ever been nomads.

      • Dan L.
        Posted August 1, 2011 at 3:05 pm | Permalink

        I should at least mention that despite the evolutionarily short timespan of 10,000 years, pastoralism does seem to have had a pretty significant effect on human evolution. Adult lactose tolerance is obviously the biggest example, and the example suggests that a disproportionate number of contemporary human beings may be descended from a relatively small number of pastoralists. So stooshie’s suggestion that nomadic lifestyles heavily influenced human evolution isn’t beyond the pale despite the arguments in my previous comment.

        I also didn’t see the follow ups where people made it clear that it’s not nomads per se but theories about early systems of governance in general.

  13. jose
    Posted August 1, 2011 at 5:14 am | Permalink

    “The fact is that people are nicer than they should be—at least according to the dictates of evolution.”

    I think you are confounding the mechanism of evolution and its effects on organisms.

  14. Torbjörn Larsson, OM
    Posted August 1, 2011 at 5:45 am | Permalink

    Evolutionary psychology? Then we _really_ need to test this.

    But it sounds good so far anyaw.

    The situation we live in today, when we can be absolutely certain that we’ll never meet someone again (as when we’re travelling), has not been in place long enough to alter our evolved behaviors.

    Does that follow? They modeled pairs, surely some spread in interactions were allowed. (The paper is, of course, paywalled.)

    Assume that realistically some spread is allowed. Then we may continue having that trait anyway, but we should also consider that “anonymous areas of society” is a temporary phenomena.

    With the new information technology, what you do in Las Vegas won’t stay in Las Vegas. An uploaded mobile shot may be trawled by photo recognition software. Soon allowing anyone to search and match for “that inconsiderate bastard’s facebook page”. (O.o)

  15. Posted August 1, 2011 at 6:02 am | Permalink

    Why is everybody assuming that the reciprocation must be a direct thing from the individual you interact with?

    Consider two societies. The first, people are only generous towards others when they anticipate that that particular other will pay back. The second, everybody is automatically always generous.

    It should be obvious that the second society will be more successful than the first.

    Now, of course, there remains the potential problem of leachers, but even that’s not so much of a problem. Most of said leachers will be the weak and infirm, and it’s most emphatically in the interests of the capable to create a society where the weak and infirm are well cared for — how else are you to expect to be cared for should your own fortunes take a turn for the worse?

    All that’s left, therefore, are the parasites. From an evolutionary perspective, all that’s necessary is to put the parasites at an overall disadvantage and time will take care of the rest. Sure enough, parasites get a reputation as such, get shunned by those around them, and effectively trade short-term gains for long-term losses. So long as that’s true in the aggregate, evolution doesn’t care so much about the outliers. More embezzlers wind up behind bars than in the Bahamas.



    • Dan L.
      Posted August 1, 2011 at 2:56 pm | Permalink

      More embezzlers wind up behind bars than in the Bahamas.

      That’s assuming we have good statistics on how many REALLY make it to the Bahamas. No one has ever called a successful embezzler an “embezzler.” (Maybe “early retiree.”) 🙂

      I’m with you about reciprocation, although in the context that you’re discussing I’ve heard and use the word “reciprocity” instead. That is, when everyone assumes everyone else is playing fair unless they have a reputation to the contrary they are practicing “reciprocity.”

      Someone with the right skill set could probably do a pretty interesting economic model based on your comparison between the two societies. Basically, the lack of trust in the reputation-driven society would increase the cost of all transactions because you’d need to spend time/money ensuring that the people you want to do business with are actually honest. There’s probably even a curve through the simulation space where the loss due to cheaters equals the loss due to transaction costs which would give some boundary conditions on markets in which reciprocity is a good policy.

  16. Posted August 1, 2011 at 8:28 am | Permalink

    1. Since behavior (response patterns) are, cet par, condition-dependent, it might be interesting to analyze “niceness” probabilistically. Surely, individuals are unlikely to be “nice” each time they have an opportunity to be…whether one-shot or iteration. Related, some organisms, e.g. humans, are likely to be very good @ predicting when it is & when it is not a good idea (worthwhile or not too costly, etc) to “act nice”. Many mechanisms are possible for such detection (e.g. greenbeard, proximity, similarities, etc).
    2. As has been suggested, frequencies, rates, durations, etc. of “nice” events will vary in time and over space. When & under what circumstances is it advantageous to “Be nice” and/or not dis-advantageous?
    3. Unless I am mistaken, Dawkins has suggested that it may (sometimes) benefit humans to be “nice” to strangers since there is some likelihood that the anonymous interaction occurs with an individual sharing some proportion of “ego’s” genes. This is testable by, for example, measuring likelihoods of “nice” across conditions with varied mixtures of genes.
    4. Since individuals are unlikely to “act nice” all of the time, maybe “act nice” is a reasonable or a default strategy under conditions of uncertainty (e.g., being in another neighborhood, however defined). Related, maybe “act nice” is, also, interpretable as a type of “bet-hedging” or low-cost sampling favored because, at least some proportion of the time, one is likely to receive more than one gives.
    5. John Hurrell Crook: “Social behavior is a subterfuge.” Relatively speaking, what are the differential costs & benefits to actor & recipient?
    6. It is hoped that the PNAS paper is important; evopsych certainly needs a boost.

  17. jay
    Posted August 1, 2011 at 9:25 am | Permalink

    I saw an interesting micro example of this a while back: in a parking lot, a gust of wind started a shopping cart heading directly toward an expensive new car. A bystander spontaneously ran after the cart and prevented the collision. The owner of the car would never know who did this, or even know that a good deed was done… but the actor probably felt some basic instinctive drive to do a good deed.

    “Imperfect discrimination is the biologically realistic case because real computational systems, such as human minds, cannot know with certainty whether an interaction is one-shot at the time the decision about cooperating must be made”

    This is a very important point. Evolution/selection does not produce a fully optimized highly discriminatory algorithm, it creates a rule that works generally good enough.

    This is also, I believe, why people protect and adopt unrelated children. Critics say evolution would never evolve such a behavior; but the behavior is not ‘calibrated’ that precisely. Our instinct to protect a child, especially one in close proximity to us, is not based on some DNA test… no, simply the proximity and the vulnerability triggers the behavior. This instinct of course benefits our natural children, but also sweeps others into the process.

  18. jose
    Posted August 1, 2011 at 9:39 am | Permalink

    We think natural selection’s way of deciding who goes above-average and below-average in terms of offspring is morally not very nice; therefore, natural selection can only produce not very nice individuals.

    Sorry that’s not true. There’s no need to look for convoluted, weird explanations. Being nice can be as effective an adaptive strategy as any other.

  19. Gregory Kusnick
    Posted August 1, 2011 at 11:04 am | Permalink

    Seems to me that there’s a third possibility being overlooked here: that we’re nice to strangers, even when nobody’s watching, because we want to think of ourselves as nice people. We have a word for people who cynically defect whenever they think they can get away with it; we call them sociopaths, and consider them them to be psychologically broken in some sense.

    Of course this just pushes the question back a level: why is it adaptive for us to want to be generous rather than selfish? The ev-psych answer, as I understand it, is that the best way to convince others that we’re trustworthy is to convince ourselves first.

  20. Matthew Dickinson
    Posted August 1, 2011 at 1:00 pm | Permalink

    Another factor is the emotions humankind has evolved that are associated with altruism
    The locomotive-locator Jerry talks about in his story wouldn’t just get the handshake and thanks, he’d feeler happier. This is (theoretically) more beneficial both in the short term, and evolutionarily speaking, than the feeling of guilt he’d get from passing by a helpless tourist. Adding to his lifetime good feelings might give him the confidence to find a mate, might avoid depression, etc.

  21. Bob Carlson
    Posted August 1, 2011 at 5:01 pm | Permalink

    Susan Blackmore has two chapters on altruism in her book The Meme Machine which I am now reading on my wife’s Kindle. There is even a funny little story relating to Susan’s Felix the Cat bike helmet. Moreover, cats are mentioned in the book 29 times. 🙂

    • Posted August 1, 2011 at 11:03 pm | Permalink

      A few months ago I tried hard to read the Blackmore book you linked to Bob. I almost gave up after 100 pages & I admit I skimmed the rest looking for stuff that wasn’t mere hand waving. I cannot take her seriously as a scientist.

      She’s on the pile of books waiting to go to the charity shop along with Sam Harris ~ he’s my biggest disappointment

      • Bob Carlson
        Posted August 2, 2011 at 10:36 am | Permalink

        It seems quite apparent that you didn’t like the book. What isn’t apparent is why. I hadn’t read more than a few of the works that Blackmore cited, so the book is interesting to me. It is a book of ideas and hypotheses on questions I hadn’t given much thought: Why humans have big brains, why humans have language. To me, it seems to provide answers for human phenomena that hadn’t yet developed when the book was written: Facebook, and Twitter, things I don’t participate in but nevertheless hear about ad nauseam. I like Blackmore’s down-to-earth writing and thinking, such as:

        Dennett (1984) has described many versions of the idea of free will and argues that some of them are worth wanting. Unlike Dennett I neither think the ‘user illusion’ is benign, nor do I want any version of free will that ascribes it to a self who does not exist.

  22. Posted August 1, 2011 at 7:18 pm | Permalink

    As per “other factors”: There is no necessary requirement that the recipient of good will be present to receive it or be aware of the gesture. Benefits to actor may derive from audience effects or “reputation”; furthermore, actor gains “bragging rights”. Unless I am mistaken, there is a mainstream literature on each of these potential benefits, among others.

  23. Posted August 1, 2011 at 9:54 pm | Permalink

    I read a lot of terms such as useful, helpful, selfish, good, nice, generosity, kindness which we today term as morality.

    Does anybody know exactly at what point in evolution did these moral traits begin to take place or in what era (year)? Do we have evidence of before and after? For something to be scientifically true it must be testable / falsifiable, if not is it not just another belief, a theory? No more than any other religion?

    • Posted August 1, 2011 at 10:45 pm | Permalink

      You ask for the year Warren ? LOL

      We do have evidence of ritual burial of the dead. The earliest undisputed human burial was 130,000 years ago, but caring for the dead most probably pre-dates humans. As you know, it is rare for land animals to fossilise & it’s even rarer to discover evidence that shines a light on behaviour

      Have you read any books on evolution ? Have you read [i]Why Evolution Is True[/i] ? What is your position on science/religion ?

      I see from the link in your name that you “follow” Apologetics 315

      Over there I found this quote that sums up the religious mindset:

      Apologetic, then, as I conceive it, is a preparer of the way of faith, an aid to faith against doubts whence-soever arising, especially such as are engendered by philosophy and science. Its specific aim is to help men of ingenuous spirit who, while assailed by such doubts, are morally in sympathy with believers. It addresses itself to such as are drawn in two directions, towards and away from Christ, as distinct from such as are confirmed either in unbelief or in faith. Defence presupposes a foe, but the foe is not the dogmatic infidel who has finally made up his mind that Christianity is a delusion, but anti-Christian thought in the believing man’s own heart ~ A. B. Bruce

      What do you think about the above quote ? Do you see the word evidence anywhere ? Do YOU think we atheists are dogmatic infidels ?

      • Posted August 1, 2011 at 11:02 pm | Permalink

        Why attack the questioner Michael?
        And yet you laugh at the question. Is it unreasonable? a logical fallacy?

        Dawkins presumes he knows at what point monkeys became humans but cannot tell when or support it with evidence. What do you call that – faith or science?

        • Posted August 1, 2011 at 11:32 pm | Permalink

          Yes, it is obviously unreasonable to expect the year delivered to you on a plate.

          Please quote some Dawkins Warren that supports your case. Have you read any of his books ? I gave you a small example of the sort of evidence we have for the evolution of moral traits in our ancestors & I could supply sources that show that many of our ape & monkey cousins alive today (& other social animals too) also exhibit tit-for-tat behaviour, caring for the sick etc.

          BUT what’s the point ? You have not answered my questions & judging by your last comment you probably deny evolution. Do you agree that we & (say) the banana share an extinct common ancestor ?

          It is a common tactic for Christians to fail to directly answer questions & to become offended ~ that seems to be you

          • Posted August 1, 2011 at 11:47 pm | Permalink

            Why is it unreasonable? If a person states a fact that fact must be supported by evidence.

            I did not answer YOUR questions because you are using circular reasoning to substantiate your answers. And it has nothing to do with my original question (Red Herring). It’s just a ploy to drive me away from my original question which is – show me the evidence for your theory.

            • Posted August 1, 2011 at 11:59 pm | Permalink

              Read back & you’ll see I did answer your original question as best as it’s possible with the current state of our knowledge. Tell me where my reasoning is circular & also answer my questions please.

              • Posted August 2, 2011 at 12:09 am | Permalink

                Well, then the ‘current state of our knowledge’ is making bold unsubstantiated presuppositions don’t you think?

        • Posted August 1, 2011 at 11:52 pm | Permalink

          Your Question:

          Dawkins presumes he knows at what point monkeys became humans but cannot tell when or support it with evidence. What do you call that – faith or science?

          There was no point at which “monkeys became humans” so I can’t call it faith nor science. Can you see the error in your statement ?

          • Posted August 2, 2011 at 12:10 am | Permalink

            I could give you a 100 reasons…

            …but I’m sure your come back would be an attack on the person 🙂

            • Posted August 2, 2011 at 7:46 am | Permalink

              Hovind is…well, the only way I could continue that sentence is by using some very impolite language, so I’ll leave that there.

              His very first claim is that there is no evidence of the Big Bang. This is patently false; the afterglow of the Big Bang is trivially directly observable in the form of the cosmic microwave background radiation. The first observations were made well before the first moon mission, so his lies — yes, lies — are simply inexcusable.

              Then he blathers on about it being impossible for stars to ignite.

              After that, the stupid gets so painful I can’t be bothered to keep listening.

              Perhaps you could pick the three reasons in that video you personally find most compelling? I’m sure you’ll understand that this is not the place to address in detail a hundred of anything.



        • Posted August 2, 2011 at 7:27 am | Permalink

          Dawkins presumes he knows at what point monkeys became humans but cannot tell when or support it with evidence.

          Oh, that’s an easy one.

          Monkeys became humans later the same afternoon when you stopped beating your wife.

          Indeed, Jerry, Richard, and all the rest of us will go to great pains to explain that the statement, “monkeys became humans,” is not just worng but most misleading.

          In Richard’s book, The Ancestor’s Tale, he has a thought experiment.

          Imagine you’re holding hands with your father, and your father is holding hands with his father (your grandfather), who in turn is holding hands with his father, and so on through time past a great many generations.

          Now, imagine a chimpanzee holding hands with his father, the chimp’s father holding hands with the grandfather, as a parallel of what you’re doing.

          What you’d find is that, a dozen million years ago or so, there’d be one single ancestor holding hands with both lineages.

          That ancestor, of course, was neither chimp nor human. And the two children holding the ur-father’s hands would be as alike as any brothers. They most likely would have each had a number of children, and their cousins would have been as alike as any cousins. As you move down the family tree closer to our time, you’ll find an overall gradual divergence. Eventually, the two clans will be discernible, such as African and Asian elephants are. With more time, the differences become more distinct, such as between tigers and lions. Even more time, and you wind up where chimps and humans are: unmistakable cousins, but unmistakably different species.

          If you continue the thought experiment not just a few million years but a thousand times longer, a few billion years, you discover that all life on the planet is related and we all — humans, chimps, cats, squid, bananas, even viruses — we all share a common ancestor.

          The evidence for this theory is overwhelming. The fossil record is exhaustive though incomplete for obvious reasons — can you identify who all your twentieth-great-grandmothers were? No? Does that mean they didn’t exist? But, as powerful as the fossil record is, it pales in comparison to genetic evidence.

          If there’re specifics in the theory that you’re hung up on, I’m sure there’re plenty here that’d be happy to help you with. If you’re just looking for a broad easy-to-read introduction, you can’t do better than Jerry’s own book whose title this Web site shares, or Richard’s latest book, The Greatest Show on Earth.



          • Posted August 2, 2011 at 8:47 pm | Permalink

            LOL… is that the gospel according to Richard? Nice parable, the only problem is it isn’t scientific. and you guys say you’re not religious. You need to have a lot of faith to believe something like that.

            Evolution is based on science, and science is based on falsifiable evidence – not some mumbo-jumbo ‘thought experiment’

            • Posted August 2, 2011 at 8:51 pm | Permalink

              … and don’t give me the ‘fossil records’ nonsense. it can only give you dates but no evidence whatsoever regarding ‘evolution’ – that is something scientists infer to postulate their conclusion. Carbon dating cannot prove evolution.

              • Posted August 3, 2011 at 5:27 am | Permalink

                I could remind you of the DNA evidence, but I can tell that you’ll respond to any form of empirical evidence by sticking your fingers in your ears and chanting, “were you there”?

                So, permit me to turn the tables.

                Were you there when Jesus insisted that Thomas fondle his intestines through his gaping chest wound? Were you there when the zombie horde descended upon Jerusalem in response to Jesus’s crucifixion? Were you there when Lazarus’s putrid, festering reanimated corpse stumbled from the grave at Jesus’s command? Were you there when a talking plant taught Moses how to wield his magic wand? Were you there when Jonah went camping in a sea monster’s belly? Were you there when Noah rode out a month and a half of storms in a hand-built wooden life raft infested with two each of every parasite? Were you there to witness that scene in the enchanted garden with the talking animals and the angry giant?


                And yet you believe such idiotic childish nonsense…why, exactly?



              • Posted August 5, 2011 at 2:30 am | Permalink

                Ben, regarding your ‘where were you’ question(s) – let me give you a modern day example.

                Lets say you come home after work one evening and find that your house was burgled. So you call the cops and they go through your house and find finger prints etc.. But then two of your neighbor comes over and tells the cops that they saw the whole thing and that they could give a detailed description of event and describe the robber himself. Now if the details matched the evidence at the crime scene and also the thief himself whom the cops are later able to apprehend, – would not the testimony of those eye-witnesses be enough to convict the thief?

                The Bible is full of first-hand eye witness accounts (1 John 1:1) and if it was a fable it would have been proven a hoax, the stories would not survive as true to this day. christian and non-christian Historians alike are in agreement to this very fact.

                I’m sure you were not there during the time of Caesar or Aristotle but I’m sure you do not doubt their writings, but as you will see the number of copies and the dates of their writings are fewer and far between.


                The new testament alone have so many copies that if it was a fraud it would have been found out a long time ago.

              • Posted August 5, 2011 at 6:03 am | Permalink

                Thanks for the laugh! That “Bible vs other ancient sources” page is a hoot! Who knew that Mark would write about the destruction of the Temple as a past historical event a full 22 years before it happened? Hilarious!

                But seriously, you need to buy a clue.

                I’ll see your insanely ludicrous assertion of an extant copy of Mark from 130 CE of an original in 48 CE, and raise you the whole of the Dead Sea Scrolls — an entire library of original documents authored by Essenes Jews in Jerusalem before, during, and after the entire possible timespan for Jesus’s alleged life. And I’ll also raise you the collected works of Philo, who was King Herod Agrippa’s brother-in-law, the philosopher who first brought the greek Logos into Judaism and who authored all the rest of Christian philosophy, who was old enough to be Jesus’s father, and who went on an embassy to Caligula in Rome in the 40s to protest against the unjust treatments of Jews. And, what the hell — I’ll also throw in Pliny the Elder and all the Roman satirists.

                You know what they all have in common?

                They were all writing between the time your zombie hero was doing his faery-tale road show and that batshit-crazy date for Mark you pulled out of your ass, and they didn’t even hint at a rumor of a possibility of anything vaguely remotely resembling something that could maybe perhaps be mistraken for Jesus.

                But never mind that. Dianetics alone has so many copies that if it was a fraud it would have been found out a long time ago. The Book of Moron, too, and the Q’ran, and the Bhagvada Gita, and the Eddas, and….

                What a maroon.

                Hey, I got some prime Arizona beachfront property for sale, real cheap. Want in on the deal?



              • Posted August 5, 2011 at 6:26 am | Permalink


                I guess it’s not only the ‘religious type’ that sends out ‘hostile’ responses. Ha Ha Ha!!!

                Ben, you are just typical of any other evolutionist/atheist. Youtube is full of the likes of you. When they cannot refute an argument they just resort to childish name-calling and abusive language. You are sad and pathetic. Enough wasting time on you.

              • Posted August 5, 2011 at 6:34 am | Permalink

                “[C]annot refute an argument”? Talk about black pots and kettles!

                So are you completely unaware of the existence and significance of the Dead Sea Scrolls, Philo, Pliny Sr., Juvenal, Martial, Petronius, Persius, Seneca, Plutarch, Justus, Damis, Epicetus, Aristides, etc., etc., etc.? Or do you just like to pretend that not a single one of them would have any cause to mention the unfolding of the greatest story ever told right beneath their very noses?

                And, really. You expect me not to laugh when you claim that Mark was authored in 48 CE and that we have a copy from 150 CE? Come on! That has to have been a joke. I mean, nobody could possibly be that cluelessly gullible, could they?



  24. Posted August 2, 2011 at 9:46 pm | Permalink

    next up: why are humans so nasty?

    • Posted August 5, 2011 at 2:06 am | Permalink

      THAT is a good question

    • Posted August 6, 2011 at 8:57 pm | Permalink

      Oxytocin, according to recent report (of course, this begs the evolutionary questions)

  25. Posted August 3, 2011 at 10:37 am | Permalink

    The trouble with Singer’s trope is that it seems to posits traits evolving rationally, “for the good of the group”, which is bad group selection: evolution postulates that there is no intentional, rational actor.

    You seem to be assuming that that an individual’s zone of reciprocity is controlled genetically, whereas it seems to me much more likely that it is controlled culturally. That is, as others have remarked, when I moved from the Big City to the Sticks, I was very much struck by how much more willing people were to interact.

    We do agree that “culture” evolves, don’t we? Much more rapidly than geneotypes.

  26. Diane G.
    Posted August 4, 2011 at 12:53 am | Permalink

    Who says altruism has to be adaptive?

    (Devil’s advocate. I actually lean toward many of suggestions in the original post & comments…)

    • CherryBombSim
      Posted August 4, 2011 at 9:43 pm | Permalink

      Aww, someone beat me to it. There seems to be so much problem explaining altruism as an adaptation that it maybe is time to think outside the box. Possibly what is evolving is the ability to convince other people to be altruistic, which is obviously beneficial to the individual. Start at birth with the parents training their kids, and you end up with a (more or less) socialized adult human. If you raised a child in total social isolation, would you expect him to behave altruistically when you let him out of his cage because of some inherited trait? I suspect not.

  27. Posted August 5, 2011 at 2:03 am | Permalink

    I can’t reply anymore?

    • Posted August 5, 2011 at 2:05 am | Permalink

      ooops.. guess I can. Sorry about this.

  28. Posted October 10, 2011 at 3:04 am | Permalink

    After reading the article, watching the video, and then reading all of the comments posted here, I’d like to submit my comment in answer to the original question, which is also the title of the article: “On the kindness of strangers: why are humans so nice?”

    The subject of Humans being nice to each other is one that I am most passionate about. I personally do not think that most Humans are that nice to each other in this day and age. But they are out there, and when I encounter them, or they encounter me (’cause I’m a kind one), it’s a good day.

    I am an American who was born in America, and sadly, this is no longer the America I grew up in. When I was a child, neighborhoods had a sense of community, and we felt safe – folks and kids alike extended common courtesies towards each other; good manners were a given. Now, I’m much older, and I see no sense of community in any neighborhood. People will tell me that they don’t even know or speak to their neighbors! I ask them, “why not?”, and they don’t know the answer!
    Conversely, I have been blessed with the kindness of strangers quite a few times in my life – perhaps it is because I am a kind individual as well; and maybe it’s some sort of harmonic resonance or brainwave thing that makes us generate towards each other.
    People can debate on “who’s right” or “who’s wrong”; or what’s accurate or inaccurate about this or that theory; or see fit to assign a certain kind of reasoning behind being kind; or say it’s because Humans have bigger brains; or what-have-you …… but I can tell you that the reason I am kind is because it’s the way I am. It’s really that simple. I’ve been kind since I was a child. It’s probable that the characteristic is not only environmental, but perhaps has a genetic propensity as well. My father was a very quite and kind gentleman; and I remember an incident that occurred when I was about 7 years old. There was an elderly couple who lived two doors down from us, and they had a retarded daughter who lived there with them. Her name was Nina, and she was approximately 45 or 50 years old, but possessed the mind & personality of a 4 or 5 year-old. Nina was quite unattractive physically, and her old parents dressed her in really odd old-fashioned clothing that was old and worn. My father sat me down one afternoon and explained what was going on with Nina, and he suggested that I might go to their house and ask her to come out and play. He told me that the fact that all the other kids in the neighborhood made fun of her was very unkind, and that he felt very bad for her parents and her; and said I would be doing a very good thing to be her friend. I told him that I was kind of scared of her because her appearance was so odd (I had never been exposed to someone like Nina before.) He reassured me that she wouldn’t hurt me. So I went down to their house and knocked on the door and asked Nina’s father if he would like me to invite her out to play. To this day, I can recall the look on that man’s face. He called Nina, and she came out and once we got to know each other a little better, I understood. Nina loved to play ball, so we’d do that most of the time, and the reward I got from giving Nina attention and the chance to play had a tremendous impact on me at age 7. It also taught me about the fact that there are people that lack things that we take for granted. That first day we played, when I walked her back up to her door, her parents thanked me profusely; and then her father offered me a quarter for playing with Nina. I told him he didn’t have to pay me to play with her; I was doing it ’cause I wanted to. When I got home and told my father about refusing the money, he was so jazzed about that and said I did the right thing – I remember he said that he guessed he’d done a good job raising me so far because my integrity was intact.
    Regardless that the people in our world around us become more & more detached, I strive to be courteous and kind to every stranger I encounter. I’m the one who will back off on a freeway to let the car next to me get in instead of speeding up so they can’t; I’m the one who is mindful of cars entering the freeway, and I’ll change lanes to allow them entry. I’m the one who; when I’m entering or exiting a convenience store, let’s say; and I see someone approaching, I’ll hold the door open for them instead of letting it slam in their face. If I see someone drop something, I’ll call their attention to it or pick it up and hand it to them.

    Last Christmas, I came out of the main Post Office one evening, and there were hundreds of people going in & out for their last minute mailing. I proceeded to pull my car around, and saw some currency on the
    ground in the crosswalk. I have always been quite poor financially, so finding it was great! I stopped the car, opened the door and scooped it up – it was a twenty dollar bill. But as I leaned down to grab it, I looked straight ahead, and directly in my line of view, was an elderly lady on crutches (the permanent polio kind); walking in the direct path the twenty was in. I also noticed that she was clutching money in her right hand; hanging out of the crutch handle. The car behind me honked for me to get moving, so I pulled ahead, and then abruptly turned back into the other side of the parking lot adjacent to where the old woman was going. Thinking to myself, “fu__!! Because even though I had only five dollars to my name and it was Christmas Eve, I really could have used that twenty. But in my heart, I knew that lady had dropped it. So I got out of my car and approached her as she had just lowered herself into her vehicle. I said, “Excuse me, ma’m; but I think you dropped some money back there – I found it right in the path where you’d been walking, and I think it’s probably yours.” She looked at me like I was from outer space and said, “Well, Heavens! I can’t believe you would return it – you’re a very nice lady!”
    I just shrugged and said, “I have to – I think it is really yours.” She said, “Well wait a minute – let me count what I have left…” Then she said, “Honey – do you need the money?” I said, “Well…. I only have five dollars to my name, but I’m certain this is yours – I found it right in the path you had just crossed; and you were holding money in your hand.” She said, “It probably is, but I am so shocked that someone in this day and age would actually demonstrate such honesty – and,when they’re in need ….” Then she took another twenty dollar bill and slapped it in my hand and said, “I want you to have this too. You’re a good girl, and I have plenty of money – you keep it; and thank you very much.”
    I exclaimed, “Wow!!” “Thank you very much, ma’m, you just made my Christmas!” She said she was very glad,and said that I had made hers too because I restored her faith in humanity. It was so cool.

    I find it an odd concept that there is a lot of focus in this subject about the reasoning behind being kind. Many times, it was mentioned that a consideration for extending kindness was, “would you see that person ever again,”, etc. or “Would it be advantageous to be kind” for some other reason. Does not that sort of mindset cancel out being kind, by default? Because if the purpose for being kind is because you might run into them again, or because it would be advantageous to you at some level, then you’re not being kind just to spread kindness. You’re being fake-kind.
    I am kind because it is the right thing to do; it’s the way I am. One person can make a difference, and it’s so easy to just be nice and courteous to each other. I have actually witnessed someone that I held a door for, hold it for someone else as I was pulling away in my car! It feels so good to be nice to other people; what say you guys all start being kind just for the purpose of being nice to each other? Like John Lennon said, “You may say I’m a Dreamer – but I’m not the only one!”
    Go out and do it! You won’t believe how good it’ll make you feel!

    Sincere Regards, Sandra

  29. Havanna
    Posted May 18, 2012 at 3:03 am | Permalink

    Do you really believet that humans are so nice to strangers?
    Personally ı do not do so..
    ingilizce tercume
    Almanca tercume
    Arapça Tercume
    Rusça Tercume

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