Category: evolutionary psychology

The Better Angels of Our Nature?: Black Friday

November 25, 2012 • 8:55 am

If you’re not an American, perhaps you don’t know about “Black Friday.” That’s the Friday after Thanksgiving Day (which falls on Thursday), and that Friday traditionally marks the beginning of the Christmas shopping season. Many stores open at midnight or early in the morning, and have incredible bargains, like waffle makers for only two dollars. Consumers line up for hours to be the first through the doors, for there is only a finite number of bargain items.

This is evolutionary psychology at work, but instead of the meat from a felled mastodon, the modern humans are fighting for consumer goods. People (both consumers and employees) have been killed in the door-opening rushes, and, on a more amusing note, there are tussles over the goods (for videos and more information on these frenzies, go here).  As far as I know, nobody was killed in this video taken two days ago, but it shows the madness of Americans that emerges on Black Friday.

God bless America!

Did human social behavior evolve via group selection? E. O. Wilson defends that view in the NYT

June 26, 2012 • 10:11 am

Here’s one last (I hope) post on the brouhaha about the evolution of social behavior that I’ve covered over the last year or so.

I think E. O. Wilson must be feeling a bit beleaguered about the criticism he’s endured for his relentless advocacy of group selection.  Not only was he an author of the Nowak et al. paper in Nature arguing that group selection rather than kin selection was the prime mover of social evolution in insects and humans—a paper that was excoriated by biologists who work on the evolution of behavior—but his new book, The Social Conquest of Earth, which makes the same group-selection argument, has also been strongly criticized.

Perhaps this explains why Wilson took to the pages of the Sunday New York Times to defend his views in an Opinionator piece called “Evolution and our inner conflict.” His thesis is this:

Within biology itself, the key to the mystery is the force that lifted pre-human social behavior to the human level. The leading candidate in my judgment is multilevel selection by which hereditary social behavior improves the competitive ability not of just individuals within groups but among groups as a whole.

“Multilevel selection” is another word for “group selection.”

How did social behavior evolve? Wilson gives a nod to kin selection, the idea that genes can evolve that produce behaviors favoring kin over oneself, so long as the genetic benefits of that behavior among all individuals outweigh the genetic costs to the altruist.  (This is weighted by the degree of kinship between actors: behaviors favoring your brothers and sisters over nonrelatives will evolve more readily than those favoring cousins over nonrelatives.)  But in the end Wilson dismisses kin selection in favor of selection among human groups:

This seems plausible, but in 2010 two mathematical biologists, Martin Nowak and Corina Tarnita, and I demonstrated that the mathematical foundations of the kin selection theory are unsound, and that examples from nature thought to support kin selection theory are better explained as products of multilevel selection.

Sadly, Nowak et al. demonstrated no such things. In fact, while they did offer what seems to be an alternative theory based on selection among groups, there is not a scintilla of evidence that it explains the evolution of social behavior in either humans or insects better than a kin-selection approach.  Their model is in fact unable to rule out kin selection, since they begin with groups that are highly related and do not vary the level of kinship in their models to determine if, as they predict, kinship is not a “driver” of social evolution.  So they simply cannot rule out kin selection as a powerful cause of social evolution.

Wilson goes on:

A strong reaction from supporters of kin selection not surprisingly ensued, and soon afterward more than 130 of them famously signed on to protest our replacement of kin selection by multilevel selection, and most emphatically the key role given to group selection. But at no time have our mathematical and empirical arguments been refuted or even seriously challenged. Since that protest, the number of supporters of the multilevel selection approach has grown, to the extent that a similarly long list of signatories could be obtained. But such exercises are futile: science is not advanced by polling. If it were, we would still be releasing phlogiston to burn logs and navigating the sky with geocentric maps.

Well, their mathematical arguments may hold, but others have shown that a). their model is basically one that does involve kin selection, and adds nothing new to the kin-selection perspective, and b). their empirical arguments about the intellectual vacuity of kin selection are serioiusly flawed. Several authors have produced lists of advances in our understanding of nature that have derived from a kin-selection perspective. In contrast, the idea of group selection has added virtually nothing to that understanding.

The number of signatories on the letters critiquing the paper of Nowak et al. is simply an indication of how much opposition their ideas faced in the scientific community. I urge readers with some biology expertise not to count the numbers, but actually read the critiques. No, science isn’t advanced by polling, but it is advanced by the open airing of arguments.  All the numbers show is that a lot of scientists—virtually every prominent worker on the evolution of social behavior—have pointed out flaws of the group-selection approach.

For a clearly written critique of Nowak, Tarnita, and Wilson’s group-selection argument for social behavior, and a lucid defense of the value of kin selection, I highly recommend a recent paper by Andrew Bourke (reference below).

But on to the evidence that we humans became altruistic and cooperative by group selection. Wilson makes a strong claim here:

In fact, it seems clear that so deeply ingrained are the evolutionary products of group selected behaviors, so completely a part of the human condition, that we are prone to regard them as fixtures of nature, like air and water.

What are these supposedly group-selected behaviors? Wilson gives three (I quote):

  • “Among them is the intense, obsessive interest of people in other people, which begins in the first days of life as infants learn particular scents and sounds of the adults around them. Research psychologists have found that all normal humans are geniuses at reading the intentions of others, whereby they evaluate, gossip, proselytize, bond, cooperate and control. Each person, working his way back and forth through his social network, almost continuously reviews past experiences while imagining the consequences of future scenarios.”

Given that we’re social animals (see below), it is to an individual’s advantage to suss out one’s fellows in the group, and to your advantage to label potentially damaging or helpful individuals as such, for they can help or hurt not only you, but your relatives.  There is no individual disadvantage that I can see to this behavior. Au contraire: any individual who can better read other people could have a reproductive advantage.  So this can evolve via individual selection; there’s no need for group selection.

  • “A second diagnostic hereditary peculiarity of human behavior is the overpowering instinctual urge to belong to groups in the first place. To be kept in solitude is to be kept in pain, and put on the road to madness. A person’s membership in his group — his tribe — is a large part of his identity.”

Yes, but why does this suggest group selection? It’s a common mistake, one pointed out by Steve Pinker in his Edge essay, to mistake adaptations for living in groups with the notion of group selection.  Cooperation can evolve by several forms of individual selection, including associating with others for protection or the ability to bring down larger prey, or through reciprocal altruism. The advantages of grouping are not only multifarious, but widespread in animals.  And if you evolve grouping behavior, then you will likely evolve the urge to want to stay in a group.  None of that needs group selection to evolve.  Given the relative difficulty of group selection compared to individual selection, it would be extraordinary if the huge variety of animals who group all evolved that trait, and the penchant to aggregate, via group selection.

And finally, some xenophobia,which is probably the flip side of the second behavior given above:

  • “All things being equal (fortunately things are seldom equal, not exactly), people prefer to be with others who look like them, speak the same dialect, and hold the same beliefs An amplification of this evidently inborn predisposition leads with frightening ease to racism and religious bigotry.”

No problem for individual selection here: if you’ve evolved to be cooperative with others in groups, but simply haven’t encountered people who are different, it is to your advantage to be suspicious of them, for they haven’t passed the test of familiarity.  Or, if groups compete with each other for food, individuals might also selected to be wary of those belonging to other groups.  That involves group competition, but not group selection.  A group-selection explanation would invoke xenophobia being maladaptive within groups, but a trait that has spread to all humans because xenophobic groups simply killed off the groups of “nice people.” That doesn’t sound so plausible to me.

 In a book review by Michael Price of Brunel University, which I’ve discussed here, Price criticizes the view that human cooperation and other social traits must have evolved by group selection, pointing out the many features of human cooperation that suggest its evolution by selection among individuals.  I won’t reprise the evidence here, but go to Price’s review (or my summary) and read the paragraph that begins as follows:

The view that group selection is needed to explain most human cooperation seems inconsistent with the fact that over the past several decades, most successful research on this cooperation has theorized that it is produced by individual-level adaptations (Price, 2011; Price and Johnson, 2011).

Price then enumerates the features of human “cooperation” that suggest it confers advantages to individuals. And if it does that, then there is no need to invoke selection among groups, which posits that “cooperative” traits are really disadvantageous for individuals within groups.

Nevertheless, Wilson blithely paints a group-selection scenario whereby the traits above, presumably disadvantageous in individuals, spread throughout the species:

Probably at this point, during the habiline period, a conflict ensued between individual-level selection, with individuals competing with other individuals in the same group, versus group-level selection, with competition among groups. The latter force promoted altruism and cooperation among all the group members. It led to group-wide morality and a sense of conscience and honor. The competitor between the two forces can be succinctly expressed as follows: within groups selfish individuals beat altruistic individuals, but groups of altruists beat groups of selfish individuals. Or, risking oversimplification, individual selection promoted sin, while group selection promoted virtue.

“Probably”? We have no evidence that altruism and cooperation evolved in this way, and suggestive evidence it evolved by individual selection—and not only in humans.  Sadly, Wilson, though at least expressing some uncertainty with the word “probably,” is severely misleading people about the evolution of cooperation.  So are others, like Jon Haidt and D. S. Wilson.  The force with which the adherents of group selection push their theory contrasts sharply with the paucity of evidence that their favorite process actually operates in nature.  It’s puzzling.  Well, maybe not so puzzling given that scientific egos and Templeton funding are on the line.

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Bourke, A. F. G. 2011. The validity and value of inclusive fitness theory. Proc. Roy. Soc. Biol. 278:3313-3320.

Trivers’s book out soon

September 30, 2011 • 11:20 am

Bob Trivers is a bit of an eccentric character, but his ideas on parental investment, parent-offspring conflict, and altruism have been landmarks in evolutionary psychology, and even though some of his ideas may be far-fetched, they’re never boring. He’s one of the most important evolutionary thinkers of our era.

I’ve just received a copy of his new book, The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life, whose thesis, as stated on the book jacket, is that “in order to deceive others, we often deceive ourselves first.” In other words, we have evolved brain “modules” to hide our own motivations, or suppress data or arguments that conflict with our genetic interests.

This is definitely a book worth reading if you’ve any interest in the evolution of human behavior, and you can get it for less than seventeen bucks on Amazon.  (It’s officially out October 25.)  This book has been in the works for a very long time: as I recall, it was originally supposed to have been co-authored with Huey Newton, a founder of the Black Panther party (now that would have been interesting!), but Newton was shot to death in 1989.

I note that the back dustflap comes with a ringing endorsement from Richard Dawkins:

This is a remarkable book, by a uniquely brilliant scientist.  Robert Trivers has a track record of producing highly original ideas, which have gone on to stimulate much research.  His Darwinian theory of self-deception is arguably his most provocative and interesting idea so far. This book is enlivened by Trivers’s candid personal style, and is a pleasure to read. Strongly recommended.

Some of the chapter titles are “Deception in nature,” “False historical narratives,” “Religion and self-deception,” and “Fighting self-deception in our own lives.”

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

July 31, 2011 • 10:29 pm
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

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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