• Print

The Biology of Being Good to Others

Scientists Richard Owen and Thomas Henry Huxley studying a water-baby in a flask; illustration designed by Linley Sambourne and engraved by Joseph Swain, from Charles Kingsley’s The Water-Babies: A Fairy Tale for a Land-Baby, 1885


Altruism may seem a good thing—unless you happen to be an evolutionary biologist. Then it may seem a mixture of a mystery and a curse. The reason isn’t hard to see. How could a ruthless process like Darwinian natural selection give rise to altruistic organisms, human or nonhuman, that act in ways that are costly to themselves and helpful to others? Darwin himself was aware of the difficulty and offered some tentative solutions, but it was during the twentieth century that altruism became the subject of nearly fetishistic attention among evolutionary biologists.

One imaginable solution is to deny that altruism really exists in nature or to claim that it’s so rare as to be unworthy of serious attention. Another solution is to construct clever theories that show how natural selection is actually expected to yield altruism. Such theories typically hinge on the level at which natural selection acts. Does it select for fitter organisms, or fitter genes, or populations, or species? Indeed the problem of altruism and the so-called levels-of-selection problem have become nearly inseparable.

David Sloan Wilson has focused on these twin biological problems for several decades. Wilson, the SUNY Distinguished Professor of Biology and Anthropology at Binghamton University, is widely regarded by biologists as a partisan in this debate. He has been the indefatigable champion of one particular theory, “multilevel selection,” for much of his career. This theory, it seems fair to say, has been a minority view among evolutionists. Ask one how altruism evolves and you are very unlikely to hear “by multilevel selection.”

But Wilson, who has written several books on evolution, does something unexpected in his new book. He announces that the problem of altruism has been definitively solved and that the levels-of-selection debate has been finally resolved. In fact it’s so resolved, he tells us, that it remains of interest only to historians of science. Does Altruism Exist? aims to present this “postresolution” view of how natural selection acts to the general reader.

As you might guess, Wilson’s own theory fares well in this postresolution view. Wilson thinks that multilevel selection (which I’ll explain below) not only accounts for altruism, it also provides a powerful way to think about, and even to help guide, the evolution of human social institutions like economies. The connection between how natural selection shapes the biological world and how human social institutions are arranged may not be obvious, but Wilson believes that the connection is both deep and important.


To begin at the end, Wilson’s answer to his titular question is yes, altruism exists. But getting to this answer requires some work. Wilson starts by distinguishing actions from thoughts. Thoughts, feelings, and rhetoric matter when it comes to altruism only insofar as they motivate actions that actually improve the welfare of a group. The actions that most matter are those that contribute to “group-level functional organization”: altruistic behavior by an individual can contribute to the smooth functioning of some group, whether an ant colony or a band of human hunters.

How can this smooth functioning of a group evolve? Wilson is certain that it’s not by selecting for the fittest individuals within a group, as the popular picture of natural selection would suggest. The reason is simple. Tradeoffs are the norm in life and when individuals act to further their own interests they generally don’t further the interests of the group. Indeed individuals can often do best by cheating, that is by shirking their group duties and looking out for numero uno.

To see this, consider an ant colony. Individual ants within a colony have specific duties depending on whether they are workers, soldiers, and so on. When every ant plays its part the colony functions smoothly. But these duties involve costs. Often, no one in the colony gets to reproduce except the queen and the rare male. And a soldier might well be called upon to sacrifice her life for the sake of the colony. A soldier might seem better off if she would cheat, abandon her soldierly duties, and reproduce. Presumably, that’s what natural selection at the individual level would have her do. In the language of biology, then, natural selection acting on individuals within groups generally won’t yield the kind of selfless behavior needed for group function.

So then how can group function and altruism evolve? Simple, says Wilson: groups that include more altruists generally perform better as groups than groups that include fewer altruists. To return to our ants, a colony in which everyone selflessly plays their part is a healthy colony that functions, survives, and ultimately gives rise to a new colony more readily than would a colony that harbors selfish ants. In the language of biology, selecting for the fittest groups can increase the number of altruists through time. Hence one of Wilson’s main conclusions: “Group-level functional organization evolves primarily by natural selection between groups.

In the real biological world, natural selection at these different levels—within groups and between groups—can occur simultaneously. And these forms of selection might have different relative strengths in different species or environmental situations. In some cases, the force of within-group selection might overwhelm between-group selection (selfishness wins) and in other cases the opposite (altruism wins, as in our ants). A mature theory of natural selection must consider all such levels, weighing mathematically their relative strengths, and determining when the interests of the group win out over the interests of the individual. That’s what the theory of multilevel selection does.

If you haven’t read many popular accounts of evolutionary biology, this likely all sounds fairly uncontroversial. But if you have, it may sound mildly scandalous. That’s because the long and acrimonious levels-of-selection debate yielded a rough consensus that selection at the group level is generally unimportant in evolution.1 Instead, biologists are far more likely to explain the evolution of traits or behaviors—including, most famously, altruism itself—by invoking natural selection at the level of genes.

This view was popularized in 1976 by Richard Dawkins in his book The Selfish Gene. But the real breakthrough came in the 1960s with W.D. Hamilton’s theory of kin selection. Hamilton saw mathematically that a gene that encourages an organism to act altruistically can actually increase in numbers from one generation to the next by natural selection if those who benefit from the altruism tend to be relatives of the altruist. The reason is that, as kin, these beneficiaries of altruistic behavior often also carry the gene for altruism. (If I carry a gene that causes me to throw myself on a hand grenade, this gene can increase in numbers through time if I preferentially save my brothers and sisters, who often carry the same gene.) Gene-level thinking about natural selection is now nearly reflexive among evolutionary biologists.

Wilson doesn’t reject this gene’s-eye view of evolution. Instead he argues for a formal equivalence. A number of evolutionary theorists have now concluded that multilevel selection theory and kin selection theory are equivalent mathematically, and this equivalence is a centerpiece of Wilson’s book. Importantly, he emphasizes that the two theories invoke the same causal processes and make the same quantitative predictions. They just do their bookkeeping—tracking the statistical consequences of natural selection—in different ways.

Something like this equivalence was first hinted at by George Price in 1972 in his famous (and famously subtle) theorem now known as the Price Equation. Price’s theorem deeply impressed Hamilton, who, later in his career, began to emphasize that kin selection and multilevel selection were closely connected. This connection has since been studied exhaustively by mathematical biologists, many of whom have arrived at the “equivalence thesis” that Wilson champions in Does Altruism Exist?

Wilson also spends some time on the general idea of equivalence in the philosophy of science. Different theories that make the same predictions but that perform their bookkeeping in different ways might often be available to scientists. (Just as, he says, different ways of keeping financial books, say by date or tax status, are available to accountants.) And these different perspectives on the same problem may often prove useful. Such equivalent views are related to, but different from, the “paradigms” of Thomas Kuhn. Whereas Kuhn considered the often-tortuous replacement of one paradigm by another—the move from Ptolemaic to Copernican cosmology, for example—Wilson argues that equivalent views “deserve to coexist.” Scientists, Wilson says, should be schooled in the idea of equivalence just as they are in hypothesis testing. This might well prevent scientists from wasting precious research time in futile debates over which bookkeeping scheme is fundamentally “correct,” a fate, he says, that plagued discussion of the levels of selection until recently.


Wilson is convinced that there’s nothing about natural selection that limits its application to traits shaped by genes. Instead, he says, natural selection can also apply to traits shaped by culture, that is by thoughts, beliefs, or, more generally, systems of symbols. Symbolic thought can affect behavior in the same way that genes can and the resulting behavior “can potentially influence survival and reproduction in the real world.” Wilson insists that this new kind of natural selection can be folded into multilevel selection theory:

Regardless of whether a phenotypic trait is genetically inherited, learned, or culturally derived, it can spread by virtue of benefitting individuals compared to other individuals in the same group, by benefitting all individuals in a group compared to other groups, and so on for a multilevel hierarchy of groups.

Wilson thus devotes the second half of his book to what multilevel selection theory has to say about human cultural phenomena like religion or economies. In each case, he hopes to determine if altruism actually exists: “How well do religions, economies, and everyday social units, such as city neighborhoods, function to improve the welfare of their members?” Importantly, in each of these cases, we’re confronted with the potentially conflicting goals of groups (say, to save the planet) and individuals (say, to maximize profits by dumping toxic waste).

Wilson is pretty sure that his multilevel selection theory of humanity can do big things for us. His claims, moreover, are not merely descriptive but prescriptive. Evolutionary theory can explain not only when the generally noble interests of groups trump the generally selfish interests of individuals, it can also help us to identify social arrangements that give an edge to the group:

If we want to solve the most pressing problems of our age, such as world peace and global environmental sustainability, then more cultural evolution is required and it must be guided by a sophisticated knowledge of evolution.

In case you’re wondering who might guide us through these treacherous evolutionary waters, Wilson describes two initiatives he helped to launch: EvoS, a “multi-institution consortium” devoted to evolutionary studies at the biological and cultural levels, and the Evolution Institute, the “first think tank that formulates public policy from a modern evolutionary perspective.”


It’s hard to exaggerate Wilson’s ambitions in this part of his book. Indeed he acknowledges considerable overlap between his project and that of Auguste Comte, the nineteenth-century positivist and great champion of a scientific religion of humanity. And Comte’s failure here doesn’t give Wilson much pause:

But Comte’s pre-Darwinian understanding of nature, the human mind, and religion are laughably old-fashioned compared to what we know today. Realizing that our own knowledge is still provisional, perhaps we are in a position to succeed where Comte and his contemporaries failed.

Wilson has written on religion before and his views in Does Altruism Exist? are fairly predictable. Religion is, he believes, false in any literal sense. But it’s common throughout humanity for good reason: religion is a group-level adaptation that spread by cultural evolution. In particular, “religions cause people to behave for the good of the group and to avoid self-serving behaviors at the expense of other members of their group.” (Wilson also claims that, somewhat surprisingly, believers typically don’t think of their behavior as altruistic; but, again, it’s actions that count.) Groups that embraced religion might therefore have outcompeted groups that didn’t, with religion spreading throughout human history by natural selection. Given its effectiveness in suppressing selfishness, Wilson, while a nonbeliever, appears respectfully tolerant of religious practice and distances himself from the heated rhetoric of “New Atheists” such as Christopher Hitchens and Richard Dawkins.

Wilson’s views on economics are newer and far more provocative. Traditional economic theory, he tells us, is based on Homo economicus, an idealized rational agent who accurately weighs costs and benefits and acts always to maximize self-interest. Economics teaches that, paradoxically, the collective action of many such agents can increase the common good.

Wilson will have none of it. He tells us about Ayn Rand’s economic fundamentalism and walks us through Flash Boys, Michael Lewis’s account of high-frequency traders on Wall Street. Recoiling in a mix of moral and intellectual horror, he announces that “it was a monumental mistake to conclude that something as complex as a large society can self-organize on the basis of individual greed.”

Fortunately, Wilson says, “evolutionary theory can set us on the right path.” Since Homo economicus acts only to increase his individual fitness within groups, multilevel selection theory shows that we can expect little group-level functional organization from him. Instead “unrestrained self-interest is far more likely to undermine the common good.” The emergence of smoothly functioning groups requires action at a different level: “Societies function well when they are a product of society-level selection.” Indeed Wilson argues that the only legitimate version of Adam Smith’s invisible hand is one that moves at the level of whole societies, sorting those economic arrangements that work from those that don’t. Wilson provides no examples here but, from his tone, it seems likely that he’d include American capitalist markets among those arrangements that don’t work for the benefit of people generally.


Does Altruism Exist? is a decidedly mixed bag. Among its strengths, Wilson clearly lays out the logic of multilevel selection theory. He is right that there is no principled reason why natural selection cannot occur simultaneously at multiple levels in the biological hierarchy, from genes, through individuals, populations, and species. And his presentation of the theory, shorn of all mathematical niceties, is among the most lucid I’ve seen. From his account we can see how selection at the between-group level can sometimes plausibly overwhelm selection at the within-group level, say, providing one way to understand the evolution of ants that act selflessly for the good of the colony.

It’s also true that many evolutionary theorists now argue that multilevel selection and kin selection are generally equivalent mathematically and they yield the same numerical predictions about the extent of genetic change from one generation to the next. Though this view is not universal, the long and fierce debate over the proper way to frame social evolution shows at least some signs of simmering down.

Wilson’s more philosophical discussion of equivalence among scientific theories generally is also strong. The fact that a process occurs in some singular way in nature doesn’t mean that there is only one legitimate way to think about it as a scientist. So long as different perspectives on a process make the same predictions and, ideally, can be translated from the language of one theory to another, it would seem absurd to argue that scientists must choose among them.

Wilson comes up short, however, in not emphasizing forcefully enough that just because different perspectives might be equivalent formally, they aren’t necessarily equivalent in the actual practice of science. Some perspectives might well be more natural, more productive, or simply easier to use than others. Indeed in evolutionary biology, it’s often easier to think about evolution in terms of the relatedness of individuals (as in kin selection) than in terms of group structure (as in multilevel selection), particularly in species where the sharp demarcation of groups is less than obvious. And it would be hard to deny that many more insights into biology—some deeply surprising—have followed from gene-level thinking than from multilevel selection thinking. Wilson doesn’t quite deny all this but I doubt that the average reader of Does Altruism Exist? would guess it.2

But it’s when Wilson turns to the social lives of human beings that his views become more problematic. There are several difficulties.

One is that Wilson’s multilevel selection theory is so broad, so causally inclusive, that it may well be able to explain nearly anything about people. When a theory allows genetic selection to act at any level in the biological hierarchy and cultural selection to act at any level in the social hierarchy, it’s hard to imagine many facts about people that might remain refractory to “explanation” by it. In science, a theory can be a little too pliant for its own good and Wilson may have found one. It would have been helpful had he listed some imaginable observations about people that would force him to seriously question his theory. Just what plausible property of religious practice, for example, might cause Wilson to conclude that multilevel selection played little part in its history? (If the early church had held that each believer should maximize his material well-being and not attend to the welfare of the community, wouldn’t Wilson conclude that Christianity spread by cultural evolution at the individual level?)3

Also, many of Wilson’s insights about society that purportedly follow from multilevel selection are frankly banal. Do we really need mathematical evolutionary theory to tell us that if we want society to successfully pursue a common goal, then individuals shouldn’t constantly cheat one another?

Part of the problem here is that Wilson inverts the actual order of logical inference. Evolutionary biologists didn’t invent the idea of individual cheaters who subvert the goals of groups. Instead, evolutionists described biological cheaters by analogy with social phenomena that were already familiar. (“This gene acts like a cheater in a game….”) We already knew that people who cheat can compromise the goals of groups and thus must be stopped. That’s why armies shoot deserters and why governments chase tax evaders. Reimporting evolutionary theory here does little but dress up these commonsensical notions in pseudoscientific garb that seems both uninformative and pretentious.

Wilson also sometimes makes things too easy for himself. This is clearest in his attempted demolition of economics, which depends heavily on omission and caricature. Reading Wilson, one would guess that economists engage in a kind of magical thinking when concluding that the pursuit of enlightened self-interest can make the world a better place. That’s partly because he never reveals the actual logic of their arguments. In an entire chapter devoted to the absurdities of economic orthodoxy, Wilson never mentions the concepts of comparative advantage or gains from trade despite their importance in economists’ arguments. Instead, he heaps ridicule on counterintuitive conclusions mostly by playing up just how counterintuitive they are. This isn’t to say that Wilson is necessarily wrong here and economists are right. But it is to say that it’s easy to win a debate when the other side’s arguments don’t get a fair hearing.

Finally, it has to be said that Does Altruism Exist? is marred by Wilson’s tendency to self-aggrandizement. In places, for example, he indulges in cringe- inducing claims about how the theory of multilevel selection, like that of Copernicus, was once derided but is now accepted. And he relentlessly insists that his version of evolutionary theory is just what is needed to right our social arrangements and save the planet. It is, I suppose, formally possible that he’s right about this. But there is precious little evidence of it in his book.

The unfortunate thing is that Wilson’s attempt to extend evolutionary theory from biology to all society distracts from his real accomplishment. He, along with many others, has helped to make the logic of natural selection clearer. And that is something. Saving the planet isn’t required.

  1. 1

    There have been dissenters from this consensus. Even Charles Darwin and Ronald Fisher, the most important evolutionists of the nineteenth and twentieth centuries, respectively, sometimes invoked selection at the group level. But the general attitude among evolutionary biologists, especially over the last several decades, has been to invoke group-level selection as a last resort. 

  2. 2

    For recent, and more technical, discussions of the equivalence thesis in evolutionary biology (including distinctions among formal, casual, and pragmatic equivalence), see Steven A. Frank’s “Natural selection. VII. History and Interpretation of Kin Selection Theory,” Journal of Evolutionary Biology, Vol. 26, No. 6 (June 2013) and Samir Okasha’s “The Relation Between Kin Selection and Multilevel Selection: An Approach Using Causal Graphs,” British Journal for the Philosophy of Science, January 20, 2015.  

  3. 3

    For more on this concern, see my previous review of Wilson’s book on the evolution of religion, Darwin’s Cathedral, in Evolution, Vol. 57, No. 1 (January 2003).