The False Allure Of Group Selection
Author: Steven Pinker
Human beings live in groups, are affected by the fortunes of their groups, and sometimes make sacrifices that benefit their groups. Does this mean that the human brain has been shaped by natural selection to promote the welfare of the group in competition with other groups, even when it damages the welfare of the person and his or her kin? If so, does the theory of natural selection have to be revamped to designate "groups" as units of selection, analogous to the role played in the theory by genes?
Several scientists whom I greatly respect have said so in prominent places. And they have gone on to use the theory of group selection to make eye-opening claims about the human condition. They have claimed that human morailty, particularly our willingness to engage in acts of altruism, can be explained as an adaptation to group-against-group competition. As E. O. Wilson explains, "In a group, selfish individuals beat altruistic individuals. But, groups of altruistic individuals beat groups of selfish individuals." They have proposed that group selection can explain the mystery of religion, because a shared belief in supernatural beings can foster group cohesion. They suggest that evolution has equipped humans to solve tragedies of the commons (also known as collective action dilemmas and public goods games), in which actions that benefit the individual may harm the community; familiar examples include overfishing, highway congestion, tax evasion, and carbon emissions. And they have drawn normative moral and political conclusions from these scientific beliefs, such as that we should recognize the wisdom behind conservative values, like religiosity, patriotism, and puritanism, and that we should valorize a communitarian loyalty and sacrifice for the good of the group over an every-man-for-himself individualism.
I am often asked whether I agree with the new group selectionists, and the questioners are always surprised when I say I do not. After all, group selection sounds like a reasonable extension of evolutionary theory and a plausible explanation of the social nature of humans. Also, the group selectionists tend to declare victory, and write as if their theory has already superseded a narrow, reductionist dogma that selection acts only at the level of genes. In this essay, I'll explain why I think that this reasonableness is an illusion. The more carefully you think about group selection, the less sense it makes, and the more poorly it fits the facts of human psychology and history.
Why does this matter? I'll try to show that it has everything to do with our best scientific understanding of the evolution of life and the evolution of human nature. And though I won't take up the various moral and political colorings of the debate here (I have discussed them elsewhere), it ultimately matters for understanding how best to deal with the collective action problems facing our species.
The first big problem with group selection is that the term itself sows so much confusion. People invoke it to refer to many distinct phenomena, so casual users may literally not know what they are talking about. I have seen "group selection" used as a loose synonym for the evolution of organisms that live in groups, and for any competition among groups, such as human warfare. Sometimes the term is needlessly used to refer to an individual trait that happens to be shared by the members of a group; as the evolutionary biologist George Williams noted,"a fleet herd of deer" is really just a herd of fleet deer. And sometimes the term is used as a way of redescribing the conventional gene-level theory of natural selection in different words: subsets of genetically related or reciprocally cooperating individuals are dubbed "groups," and changes in the frequencies of their genes over time is dubbed "group selection." To use the term in these senses is positively confusing, and writers would be better off referring to whichever phenomenon they have in mind.
In this essay I'll concentrate on the sense of "group selection" as a version of natural selection which acts on groups in the same way that it acts on individual organisms, namely, to maximize their inclusive fitness (alternatively, which acts on groups in the same way it acts on genes, namely to increase the number of copies that appear in the next generation; I will treat these formulations as equivalent). Modern advocates of group selection don't deny that selection acts on individual organisms; they only wish to add that it acts on higher-level aggregates, particularly groups of organisms, as well. For this reason, the theory is often called "multilevel selection" rather than "group selection." This all sounds admirably ecumenical and nonreductionist, but my arguments will also apply to multilevel selection. I don't think it makes sense to conceive of groups of organisms (in particular, human societies) as sitting at the top of a fractal hierarchy with genes at the bottom, with natural selection applying to each level in parallel ways.
First I'll examine the idea that group selection is a viable explanation of the traits of human groups such as tribes, religions, cultures, and nations. Then I'll turn to group selection as an explanation of the traits of individual humans, that is, the intuitions and emotions that make it possible for people to learn their culture and coexist in societies. (No one denies that such faculties exist.) Finally I'll examine the empirical phenomena that have been claimed to show that group selection is necessary to explain human altruism.
1. Group selection as an explanation of the traits of groups.
Natural selection is a special explanatory concept in the sciences, worthy, in my view, of Daniel Dennett's designation as "the best idea that anyone ever had." That's because it explains one of the greatest mysteries in science, the illusion of design in the natural world. The core of natural selection is that when replicators arise and make copies of themselves, (1) their numbers will tend, under ideal conditions, to increase exponentially; (2) they will necessarily compete for finite resources; (3) some will undergo random copying errors ("random" in the sense that they do not anticipate their effects in the current environment); and (4) whichever copying errors happen to increase the rate of replication will accumulate in a lineage and predominate in the population. After many generations of replication, the replicators will show the appearance of design for effective replication, while in reality they have just accumulated the copying errors that had successful replication as their effect.
What's satisfying about the theory is that it is so mechanistic. The copying errors (mutations) are random (more accurately, blind to their effects). The outcome of interest is the number of copies in a finite population. The surprising outcome is a product of the cumulative effects of many generations of replication. If the copying errors were not random (that is, if Lamarck had been correct that changes in an organism arise in response to a felt need, or if creationists were right that a superior intelligence directed mutations to be beneficial to the organism), then natural selection would be otiose—the design could come from the mutation stage. If the outcome of interest were not the number of copies in a finite population, but some human-centered criterion of success (power, preeminence, influence, beauty), then natural selection would not be mechanistic: the dynamics of change in the population could not be mathematically computed from its prior state. And if it took place in a single generation, then natural selection would be banal, since it would add nothing to ordinary physical cause and effect. When a river erodes the soft rock layers on its bed and leaves behind the harder layers, or when the more volatile compounds in petroleum evaporate faster than the less volatile ones, one hardly needs to invoke the theory of natural selection. One can just say that some things are stronger, or longer-lasting, or more stable than others. Only when selection operates over multiple generations of replication, yielding a cumulative result that was not obvious from cause and effect applying to a single event, does the concept of natural selection add anything.
The theory of natural selection applies most readily to genes because they have the right stuff to drive selection, namely making high-fidelity copies of themselves. Granted, it's often convenient to speak about selection at the level of individuals, because it's the fate of individuals (and their kin) in the world of cause and effect which determines the fate of their genes. Nonetheless, it's the genes themselves that are replicated over generations and are thus the targets of selection and the ultimate beneficiaries of adaptations. Sexually reproducing organisms don't literally replicate themselves, because their offspring are not clones but rather composites of themselves and their mates. Nor can any organism, sexual or asexual, pass onto its offspring the traits it has acquired in its lifetime. Individual bodies are simply not passed down through the generations the way that genes are. As Stephen Jay Gould put it, "You can't take it with you, in this sense above all."
Now, no one "owns" the concept of natural selection, nor can anyone police the use of the term. But its explanatory power, it seems to me, is so distinctive and important that it should not be diluted by metaphorical, poetic, fuzzy, or allusive extensions that only serve to obscure how profound the genuine version of the mechanism really is.
To be sure, some extensions of natural selection to replicators other than genes are rigorous and illuminating, because they preserve the essential features of replicator dynamics. Examples include bits of code in genetic algorithms, the analogs of genes in artificial-life simulations, and, if the physicist Lee Smolin is correct, the laws and constants of entire universes.
But other extensions are so poetical that they shed no light on the phenomenon and only obscure the real power of natural selection. There's no end to the possibilities for pointlessly redescribing ordinary cause-and-effect sequences using the verbiage of natural selection. Cities have more old buildings made of stone than of wood because of the process of edifice selection. Cars today are equipped with steel-belted radials because they outcompeted polyester-belted tires in a process of tire selection. Touch-tone phones have prevailed over dial phones because of their competitive advantages in telephone selection. And so on. Sure, some things last longer or do better in competition than others because they have traits that help them last longer or compete more effectively. But unless the traits arose from multiple iterations of copying of random errors in a finite pool of replicators, the theory of natural selection adds nothing to ordinary cause and effect.
What about groups? Natural selection could legitimately apply to groups if they met certain conditions: the groups made copies of themselves by budding or fissioning, the descendant groups faithfully reproduced traits of the parent group (which cannot be reduced to the traits of their individual members), except for mutations that were blind to their costs and benefits to the group; and groups competed with one another for representation in a meta-population of groups. But everyone agrees that this is not what happens in so-called "group selection." In every case I've seen, the three components that make natural selection so indispensable are absent.
(a) The criterion of success is not the number of copies in a finite population (in this case, the meta-population of groups), but some analogue of success like size, influence, wealth, power, longevity, territory, or preeminence. An example would be the "success" of monotheistic religions. No one claims that monotheistic religions are more fission-prone than polytheistic ones, and that as a consequence there are numerically more monotheistic belief systems among the thousands found on earth. Rather, the "success" consists of monotheistic religions having more people, territory, wealth, might, and influence. These are impressive to a human observer, but they are not what selection, literally interpreted, brings about.
(b) The mutations are not random. Conquerors, leaders, elites, visionaries, social entrepreneurs, and other innovators use their highly nonrandom brains to figure out tactics and institutions and norms and beliefs that are intelligently designed in response to a felt need (for example, to get their group to predominate over their rivals).
(c) The "success" applies to the entity itself, not to an entity at the end of a chain of descendants. It was the Roman Empire that took over most of the ancient world, not a group that splintered off from a group that splintered off from a group that splintered off from the Roman Empire, each baby Roman Empire very much like the parent Roman Empire except for a few random alterations, and the branch of progeny empires eventually outnumbering the others.
On top of these differences, most of the groupwide traits that group selectionists try to explain are cultural rather than genetic. The trait does not arise from some gene whose effects propagate upward to affect the group as a whole, such as a genetic tendency of individuals to disperse which leads the group to have a widespread geographic distribution, or an ability of individuals to withstand stressful environments which leads the species to survive mass extinction events. Instead, they are traits that are propagated culturally, such as religious beliefs, social norms, and forms of political organization. Modern group selectionists are often explicit that it is cultural traits they are talking about, or even that they are agnostic about whether the traits they are referring to are genetic or cultural.
What all this means is that so-called group selection, as it is invoked by many of its advocates, is not a precise implementation of the theory of natural selection, as it is, say, in genetic algorithms or artificial life simulations. Instead it is a loose metaphor, more like the struggle among kinds of tires or telephones. For this reason the term "group selection" adds little to what we have always called "history." Sure, some cultures have what it takes to become more populous or powerful or widespread, including expansionist ideologies, proselytizing offensives, effective military strategies, lethal weaponry, stable government, social capital, the rule of law, and norms of tribal loyalty. But what does "natural selection" add to the historian's commonplace that some groups have traits that cause them to grow more populous, or wealthier, or more powerful, or to conquer more territory, than others?
2. Group selection as an explanation of the traits of individuals.
Let's now turn to the traits of individuals. Is group selection necessary to explain the evolution of psychological traits adapted to group living such as tribalism, bravery, self-sacrifice, xenophobia, religion, empathy, and moralistic emotions? This section looks at theory, the next one at psychological and historical data.
The reproductive success of humans undoubtedly depends in part on the fate of their groups. If a group is annihilated, all the people in it, together with their genes, are annihilated. If a group acquires territory or food or mates, the windfall will benefit some or all of its members. But recall the fleet herd of deer and the herd of fleet deer. If a person has innate traits that encourage him to contribute to the group's welfare and as a result contribute to his own welfare, group selection is unnecessary; individual selection in the context of group living is adequate. Individual human traits evolved in an environment that includes other humans, just as they evolved in environments that include day-night cycles, predators, pathogens, and fruiting trees.
Some mathematical models of "group selection" are really just individual selection in the context of groups. The modeler arbitrarily stipulates that the dividend in fitness that accrues to the individual from the fate of the group does not count as "individual fitness." But the tradeoff between "benefiting the self thanks to benefiting the group" and "benefiting the self at the expense of the rest of the group" is just one of many tradeoffs that go into gene-level selection. Others include reproductive versus somatic effort, mating versus parenting, and present versus future offspring. There's no need to complicate the theory of natural selection with a new "level of selection" in every case.
It's only when humans display traits that are disadvantageous to themselves while benefiting their group that group selection might have something to add. And this brings us to the familiar problem which led most evolutionary biologists to reject the idea of group selection in the 1960s. Except in the theoretically possible but empirically unlikely circumstance in which groups bud off new groups faster than their members have babies, any genetic tendency to risk life and limb that results in a net decrease in individual inclusive fitness will be relentlessly selected against. A new mutation with this effect would not come to predominate in the population, and even if it did, it would be driven out by any immigrant or mutant that favored itself at the expense of the group.
Let's take the concrete example of collective aggression. Often the benefits to the self and to the group may coincide. A warrior may scare off a party of attackers and save the lives of his fellow villagers together with the lives of himself and his family. In other cases the benefits may diverge: the warrior may stay at the rear, or sneak off to the side, and let everyone else fight. In still others the outcome may be uncertain, but because selection works on probabilities, he may play the odds, say, taking a one-in-ten chance of getting killed in a raid that promises a one-in-two chance of abducting a few extra wives. We should expect selection to favor traits that maximize the individual's expected reproductive output, given these tradeoffs.
What we don't expect to see is the evolution of an innate tendency among individualsto predictably sacrifice their expected interests for the interests of the group—to cheerfully volunteer to serve as a galley slave, a human shield, or cannon fodder. Take the extreme case of a gene that impelled a person to launch a suicide attack that allowed his group to prevail over an enemy. That is hardly a gene that could be selected! (I'll put aside for now the potential benefits to the suicide warrior's kin.) What could evolve, instead, is a tendency to manipulate others to become suicide attackers, and more generally, to promulgate norms of morality and self-sacrifice that one intends to apply in full force to everyone in the group but oneself. If one is the unlucky victim of such manipulation or coercion by others, there's no need to call it altruism and search for an evolutionary explanation, any more than we need to explain the "altruism" of a prey animal who benefits a predator by blundering into its sights.
Thus we have a nice set of competing empirical predictions for any examples of group-benefiting self-sacrifice we do observe in humans. If humans were selected to benefit their groups at the expense of themselves, then self-sacrificial acts should be deliberate, spontaneous, and uncompensated, just like other adaptations such as libido, a sweet tooth, or parental love. But if humans were selected to benefit themselves and their kin in the context of group living (perhaps, but not necessarily, by also benefiting their groups), then any guaranteed self-sacrifice should be a product of manipulation by others, such as enslavement, conscription, external incentives, or psychological manipulation.
To be sure, if we go back to group selection as an explanation of group traits, particularly cultural ones, then it's easy to see how a group that successfully coerced or manipulated a renewable supply of its own members to launch suicide attacks might expand relative to other groups. But that would have nothing to do with its members' inherited psychology, in this case, their willingness to sacrifice themselves without manipulation. The same is true for less extreme sacrifices.
Read more at Edge