The Evolution of Altruism

Author: Harman, Oren

Originally published on The Chronicle of Higher Education website, February 9, 2015. Retrieved from

It’s one of my favorite Darwin quotes—"He who understands baboon would do more toward metaphysics than Locke"—scribbled furtively in a notebook between visits to the London Zoo in the summer of 1838. Twenty-one years would pass before On the Origin of Species would shock the world, but Darwin already knew: If man wanted to comprehend his mind, he’d need to train an unflustered gaze into the deep caverns of his animal past.

The issue at hand was whether knowledge was innate or based entirely on experience, two doctrines referred to as rationalism and empiricism, between whose partisans, wrote John Stuart Mill, "reigns a bellum internecinum [in which] even sober men on both sides take no charitable view of each others’ opinions." Ahead of his time, Darwin sought to combine the two—a helping of Kant with a scoop of Locke—in man as much as in the animals. But there was a crucial consequence: Morality is a matter of biology as much as tradition, religion, or law.

Ever since Darwin glimpsed virtue’s natural origins, cooperation and altruism have been the provenance of natural scientists as much as economists, philosophers, and students of culture. Colorful characters have been the norm: from the Russian anarchist prince and naturalist Peter Kropotkin, to the British Marxist geneticist J.B.S. Haldane, to the enigmatic American George Price, who, as a homeless drifter who’d given away all his possessions to the poor, slit his throat in a London squat in 1975 over an equation he had written regarding the possibility of genuine kindness.

The altruism game is as alive today as it has ever been. Evolutionary theorists, brain scientists, animal behaviorists, child psychologists—all are alight after the Holy Grail: to put to rest millenniums of debate concerning the nature of man, good or bad. Christianity may have it that Original Sin is redeemed by Christ’s sacrifice, but biology probes the evolutionary paths and, increasingly, the neurons and hormones that render good will and giving part and parcel of who we are, whether free thinkers or believers.

What have the scientists learned?

A new book by David Sloan Wilson provides some thoughtful answers. Wilson is a professor of biology and anthropology at Binghamton University, and one of the leading evolutionary theorists of his generation. He has written scholarly and popular books on the evolution of altruism, religion as a multilevel adaptation, and, in The Neighborhood Project: Using Evolution to Improve My City, One Block at a Time (Little, Brown and Company, 2011), on applying evolutionary principles to better the quality of life in Binghamton, N.Y. His new book, Does Altruism Exist? Culture, Genes, and the Welfare of Others, is part of a series of little books on big ideas from Yale University Press, and a concise summary of his life’s work.

Like Darwin, Wilson begins with the animals, specifically bees, which, when their colony splits by swarming, send out scouts to search out a new nest cavity. Miraculously, when the individual scouts return, each having visited a cavity or two at most, and therefore lacking the requisite big picture to "argue" their case, a collective decision about the best option is nonetheless made based on their dancelike interactions. This collective process is uncannily similar in pattern to the one observed between individual neurons in the brains of rhesus monkeys that are trying to determine the principal direction of movement of haphazard dots on a screen. The "group mind" of the bees seems to work in almost identical ways to the single, multimillion-neuron mind of the monkey.

And that is not all. Before sunset on the African plains, female buffaloes determine where the herd will graze next by pointing their heads distinctively in a certain direction; somehow each nod is integrated and the direction with the most "votes" chosen. Pelicans form half-circles, paddling in unison to trap coastal fish. Tadpoles communicate via surface waves to make collective decisions about which food sources to tap. Even bacteria use quorum sensing to coordinate gene expression according to the density of their population. How does such seemingly incredible group functionality come about? According to Wilson, the answer can be found in a few basic evolutionary principles.

All of evolution, he argues convincingly, can be stated on one foot, akin to Rabbi Hillel’s condensation of the Bible ("Do unto others as you would have them do unto you"). It goes like this: "Selfishness beats altruism within groups. Altruistic groups beat selfish groups. All else is commentary." Here’s the reason: Since natural selection is based on relative fitness rather than absolute fitness, all that matters for an organism is that it be in better shape than its neighbors; jumping highest or eating the most in an absolute sense is meaningless. Except that "putting out" for the group, in the form of costly cooperation or outright sacrifice, necessarily reduces the relative fitness of the individual.

So there is a conflict: Should one look out for oneself or the tribe? The conflict is complicated by the fact that cooperative groups do better than less altruistic ones. Group functionality will therefore almost invariably evolve by natural selection working between groups rather than within them. The organism-like quality of groups of bees and buffaloes and pelicans and tadpoles and bacteria have the successful suppression of individual urges to thank.

Figuring out the mechanisms that give birth to group cohesion by blocking individual selfishness is therefore an important evolutionary agenda. It helps to explain the origin of life, how single cells came together to form multicellular creatures, and why, among social insects like bees, ants, wasps, and termites, but also mammals like the blind African mole rat, entire castes forgo reproduction, devoting their lives instead to the greater good. It is also a key to fighting cancer. There is a tradition, going back nearly a century, of biologists’ searching out the secrets of the "superorganism," and D.S. Wilson has been one of its prominent modern practitioners.

His has been an uphill battle. Ever since the 1960s, biologists have ridiculed so called "group selection." Countering such arguments, Wilson provides the clearest explanation I have seen yet of how selfish-gene theorists, evolutionary-game theorists, and kin selectionists all employ group-selection logic without realizing or admitting it. All of these competing approaches merely represent different ways of looking at the same problem, accounting mechanisms rather than distinct ontological descriptions.

Kin-selection theory explains sterility in social insects, for example, by claiming that the workers are improving their own fitness by assisting reproduction in the queen, whereas multiselection theory understands sterility as providing a collective benefit to the colony. The explanations may sound different, but, unlike competing paradigms, the alternative renderings deserve to coexist, since they needn’t be incommensurable. It’s just like arranging expenditures by date versus arranging them by dollars, or describing a mountain peak from two different angles.

Understanding this helps to clarify how a behavior that looks altruistic from one perspective can seem selfish from another. It also demands that the controversy over group selection go the way of the debate over Copernicanism, Darwinism, and continental drift. Does altruism exist? Of course it does, replies Wilson, with regard to the theory of multilevel selection, and it has done no less than to shape our planet.

Things get more complicated when we graduate to man. That’s because biological altruism is defined by the result of an action, while psychological, or human, altruism, is all about intent. An amoeba, by a certain action, confers a fitness benefit on another while incurring a fitness cost and so is considered an altruist. But a person can act altruistically for many a reason: moral rectitude, gratification from another’s pleasure, to put someone in one’s debt, to better one’s reputation, to receive an ultimate reward. With the many-to-one relationship between intent and action governing the human condition, how is one to make out a true altruist from a masquerading narcissist?

Wilson doesn’t know, but he doesn’t much care, either. The important point is that the same dynamic governing the birth of altruism in nature applies to man. Because of the demands of child care and hunting and gathering, along with the need to defend against predators and fight against competing human groups, between-group selection superseded within-group selection, rendering our species evolution’s latest major transition. Developing the biological and cultural mechanisms that suppressed disruptive within-group competition and fostered empathy and trust, our ancestors became the sole primate, in Wilson’s words, to "cross the threshold from groups of organisms to groups as organisms." Like all major transitions in evolution, it was a rare event with major consequences. All else is commentary.


But if Wilson pulls back from entering the mind, focusing instead on evolutionary dynamics, a cottage industry has grown in recent years around theories purporting to explain how our brains produce empathy, morality, and good will. One recent example comes from Donald W. Pfaff, a professor of neurobiology at Rockefeller University. Stepping, as he says, out of his "comfort zone" studying steroid hormones’ effects on nerve cells in mice, Pfaff argues that recognizing our inborn goodness can add to our capacity for benevolence. "If a person simply realizes that he is wired for good, altruistic behavior and behaves accordingly," he promises, "and if the person toward whom he is about to behave does the same thing, then everything is likely to come out OK." Happily, "science now knows that we are wired to empathize." Really, it isn’t all that complicated.

In The Altruistic Brain: How We Are Naturally Good, a self-described "perfect storm of audacity, awareness, and insight," Pfaff promises a revolution. "We are accustomed to this kind of storm in, say, the humanities, when suddenly there is Modernism or the French New Wave. Well, the same kind of sudden actualization can happen in science as well." The actualization? "After centuries of debate over whether humanity is fundamentally flawed (as blamed on Eve) or particularly benevolent (as proposed by the philosopher David Hume), neuroscience is ready to provide an answer: We are good." What a relief.

What Noam Chomsky did for language, Pfaff claims to do for kindness (never mind that Chomsky’s wall is being torn down these days). Since all social behavior is the product of the brain, if we just understand how the brain works, he writes, "we can design a rational system of ethics having more predictable outcomes. ... Technical neuroscience can be applied to actual social problems that until now have seemed intractable." Domestic bliss, social harmony, and world peace are within our grasp. Welcome, all, to a brave new world.

How does it work? Pfaff presents ABT—altruistic-brain theory—a simple five-step recipe for good behavior, accomplished in a few hundredths of a second mostly below the radar of our consciousness. First, the central nervous system registers the act you are about to perform toward another—say, running into a burning building to save someone. Second, you mentally picture the person who will be the beneficiary of your action, say, a child stuck in her flaming room. Third, the image of that child blurs and meshes with an image of yourself—you literally see yourself as a beneficiary of your own action. Fourth, neurons in your prefrontal cortex vote "thumbs up" or "thumbs down" on the intended action, translated emotionally into feelings of "good" or "bad." Finally, if the vote was positive, you act; if the feeling was disturbing, you demur. What Pfaff argues is that the default of our brains is to act in ways that are altruistic toward others. Choosing self over other is secondary and less "natural."

How does he know? Well, he doesn’t really. The evidence Pfaff provides is mainly inferential. Yes, the same nerve cells that command muscles to contract send a second, identical message back to the brain’s sensory systems—a phenomenon called "corollary discharge," which accounts for Step 1. But what evidence exists that we absolutely cannot act toward another person unless we visualize that person—or at the least a generic human being? Very little. And how does the image of the little girl in the burning room merge with our own? Pfaff’s answer is that an increase in the excitability of cortical neurons takes place such that the nerve cells representing the child fire at the same time as those representing oneself. Why? Because there exist three cellular mechanisms correlated with excitability.

But is there evidence that they, in fact, do what he claims, superimposing one image over another? None that I know of—it’s just a theoretical possibility. Perhaps aware of the shakiness of his argument, Pfaff throws "mirror neurons" into the mix, like an extra log meant to stoke his fire, but seems unaware of the many serious critiques of the hype they’ve engendered. The neuroscientist Vilayanur Ramachandran may have predicted that "mirror neurons will do for psychology what DNA did for biology," but the notion that they play a causal role in allowing us to understand the goals behind people’s actions, and hence to empathize, is strongly challenged by the fact that we are perfectly able to understand actions we ourselves can’t perform—like flying, or speech by the mute. And when Pfaff claims that since blurring the image of the recipient of the altruistic act is de facto a loss of information, ergo energetically cheap, ergo plausible, hence confirmation of Step 3, he reduces the standard of scientific argument considerably. Things aren’t true because they’re plausible. They become true when they are observed, and even then not always.

Pfaff cites the work of the Harvard neuropsychologist Joshua Greene as evidence for Step 4. Using functional magnetic resonance imaging, Greene has devised a number of clever experiments to tease out the anatomical correlates of specific moral judgments, like deciding whether to steer an out-of control trolley into one person in order to avoid killing five. Greene has zeroed in on a part of the brain called the dorsolateral prefrontal cortex, showing its association with rational judgments made in the context of competing emotional responses. What precisely such correlations mean is argued by thoughtful interlocutors, some of whom refer to today’s use of fMRI as a "21st-century phrenology." Seemingly oblivious to such debates, Pfaff proposes an as yet unseen "emotional switch" somewhere in the neural circuitry between the prefrontal cortex and the amygdala, a switch that determines whether or not one will act altruistically toward another human being.

All we need to do to "increase the performance of the brain’s neuronal circuitry" is to create the right environments—small classrooms, fewer vagrants walking the streets, less corruption and bullying, more women in positions of power, after-school games, curfews, self-aware politicians—and the sought-after physiology will appear. With the right amounts of oxytocin, vasopressin, and corticotropin-releasing hormone, a benevolent brew baked into our brains by evolution, the switch will be flicked on, he writes, so as "to help us do the job of making an ethical decision."

There’s nothing wrong with offering a guess and calling it a theory; the history of science teaches that this is a preferred method for gaining insight into ourselves and the world. Unfortunately, many popularizers of brain research slip imperceptibly between arguing for theoretical possibilities and stating them as fact. Many lack humility. You could do worse than arming yourselves with Sally Satel and Scott O. Lilienfeld’s Brainwashed: The Seductive Appeal of Mindless Neuroscience (Basic Books, 2013) to train yourself to recognize what has been termed "brain overclaim syndrome" when you see it. As reductionist caricatures infiltrate the medical, educational, and legal systems, we should all be on the lookout.

Not that we haven’t learned a great deal in recent years about the neurochemistry of behavior. Oxytocin, for one, is a fascinating little molecule. This tiny neuropeptide, which is more than 700 million years old, was gradually co-opted from regulating water and mineral levels in the bodies of terrestrial animals to being involved in the function of the placenta and the workings of lactation, in uterine contractions, and in suckling and attention in female mammals. Evolution being the master tinkerer, the ambit of such caring behavior was eventually extended from kin to kith.

We now know that complex social behaviors, whether pair bonding or promiscuity, are strongly related to the density of receptors for oxytocin in the brains of voles, marmosets, titi monkeys, and the California deer mouse. In humans, cocaine-using mothers have lower levels of oxytocin and display less maternal behavior, while healthy fathers injected with the molecule via a nasal spray show markedly more affection toward mothers and kids. Even the business world has taken notice: Subjects administered sniffs before playing an economic game in which trust plays a decisive role in success were found to be more trusting in others and hence more successful. Various companies are already advertising oxytocin nasal spray on the Internet.

This is fascinating stuff, but it’s far from a Holy Grail. For one thing, single genes rarely have large effects, more often than not playing a role in a host of bodily functions. The relatively simple physical trait of height, for example, is known to be associated with 54 alleles (DNA codings), which collectively account for only 5 percent of heritability—the rest’s a mystery. And, of course, mental traits like depression and empathy are enormously more complicated. As the philosopher Patricia Churchland shows nicely in her book Braintrust: What Neuroscience Tells Us About Morality (Princeton University Press, 2011), the molecule serotonin, for instance, figures in cardiovascular regulation, respiration, circadian rhythm, sleep-wake cycles, appetite, aggression, sexual behavior, sensorimotor reactivity, pain sensitivity, and reward learning. And oxytocin, after a point, suddenly triggers the weakening of mate attachment in female prairie voles rather than the reverse. Drug developers know that the notion of linking a particular gene or gene product to a particular phenotype is at best naïve and usually plain wrong. Neuroscience deserves our public funds, to be certain, but there is much work yet to do.


Which brings us back to David Sloan Wilson. Humans became functionally organized, he and others argue, through child care, food acquisition, predator defense, and trade and warfare with other groups. Each of these required mutual aid and the suppression of the interest of individuals, which meant the creation of brains that know both how to empathize and how to make moral judgments, including when to punish someone who steps out of line. A likely scenario is that as a neural reward-and-punishment system became linked to internalizing social practices in human evolution, it created a feedback loop bonding culture to biology. Our brains do not arrive ex nihilo. They’ve been shaped by thousands of generations of gene/culture evolution.

And so, yes, bodies are crucial for understanding behavior: There exist no human traits divorced from biology, and without our bipedalism and larynx and prefrontal cortex suffused in molecules like oxytocin, we would not be who we are. But figuring out our biology is both absolutely necessary and completely insufficient. That is because we were forged in a collective caldron, our species the result of interactions among our progenitors. And as agriculture made us sedentary, and our numbers grew, so too did the importance of language and culture. Human populations spread across the globe and invented different ways of life. Unique geographic environments produced unique solutions to such problems as sharing resources, dividing labor, and living together peacefully.

To understand how different solutions came about, we need to study the construction of entire social environments, not just what motivates individuals, much less the biology of individual brains. Margaret Thatcher may have believed that "there is no such thing as society," and an entire social philosophy, "methodological individualism," may have taken over economics and sociology for a time. In neuroscience, a certain cast of mind may now interpret different religions’ advocacy of the Golden Rule as evidence of a common underlying biology. But the truth is that ethics is a collective property, not a denizen of any particular mind—"Art is myself, science is ourselves," Claude Bernard quoted Victor Hugo on Shakespeare—and so is morality.

What this means is that history and culture matter. No, Modernism didn’t suddenly materialize in "a storm," nor should we take seriously anyone who promises that Congressional squabbles or Middle Eastern conflicts will miraculously dissolve because of the parties’ realization of Pfaff’s altruistic-brain theory. Neuropeptides and cortical anatomies are no replacement for the deep, multilayered contextualizations of history, anthropology, or international relations. The historian of Victorian England G.M. Young once wrote: "My aim is to read in a period until I can hear its people speak." When we approach our past, trying to put our finger on cooperation and trust, besides literatures we should use archaeological remains, weather models, linguistic analysis, and careful study of custom and material culture to aspire to a similar standard.


But what about our present? The world is complicated, full of violence and warfare. At times our "superorganism" seems on the verge of disintegrating. In The Paradox of Generosity, the Notre Dame sociologist Christian Smith and his student Hilary Davidson argue alongside Jesus and Muhammad and Ecclesiastes that through giving we receive. "Help your brother’s boat across," they quote a Hindu proverb, "and your own will reach the shore." What’s new, they claim, is that science now corroborates the sages: According to five measures of well-being tabulated in a nationwide study, the Science of Generosity Initiative, misers are indeed miserable and the generous are happier, as long as giving is a basic part of their lives; onetime donations of blood and even organs fail to spark the feel-good magic.

Never mind the problem of reverse causation. What the authors find, to their astonishment, is that despite the obvious perk, Americans are lousy altruists. Only 2.7 percent tithe, while 41 percent donate something less than 2 percent of their earnings, and 45 percent give nothing at all. Less than a quarter volunteer, and 42 percent have never taken care of someone else’s children. Religions promise an afterlife, but according to the Notre Dame authors, science can do better: "If Americans want to be happier, healthier people who live with greater purpose, suffer less depression, and enjoy more personal growth, [they should] learn to be more generous."

Hold on a minute. Isn’t sacrifice the point of altruism? Maybe it is, and maybe it isn’t. I’m not really sure. More interesting is the possibility that despite all the madness and just plain egoism around us, there might exist rules of cohesion to help us stick together. The late economist Elinor Ostrom won a Nobel Memorial Prize in Economic Science in 2009 for showing that there are universal design principles that help different cultures find solutions to managing common resources like pastures and forests, fisheries and irrigation systems. Strong group identity, an agreed-upon system for rewarding members for their contributions, collective-choice arrangements, monitoring, graduated sanctions, conflict-resolution mechanisms, and the authority to run their own affairs all figure in the subversion of the economist Garrett Hardin’s "tragedy of the commons." They are as crucial to groups as organs are to individuals. What is interesting about this list is that cooperation and altruism are not simply born out of fuzzy good will. They require action that itself is not altruistic, like punishment and ostracism, the crushing of personal whims, the selfish exercise of authority. Sadly, they often also require a reviled "other" to sustain intergroup togetherness—a legacy, it would seem, of our clannish beginnings. That is a hurdle we have yet to learn to overcome, and maybe our greatest challenge.

But there are many ways to foster identity, fortify authority, and fabricate "others," drawing on different norms and social conventions. That is the good news, a tonic against universalists. David Sloan Wilson is president of the Evolution Institute, the first think tank to formulate public policy from a modern evolutionary perspective, and he has turned Binghamton into a citywide experiment. Like a conservation biologist trying to figure out how to help plants grow, he and his team are using evolutionary logic, and Ostrom’s principles, to build local "ecological niches" that nurture cooperation and trust. What they are beginning to learn is the precise opposite of the Notre Dame conclusion: Those who receive, give. It seems a better verdict. But the task won’t be easy, and I wish him luck.

And so the altruism game continues. Darwin was right: There is much to learn about metaphysics from baboons. Peering into our evolutionary past and our brains, we will doubtless learn more in the future about the physical elements and social arrangements that allow us to slip, mentally, into someone else’s shoes, feel guilty about turning away a beggar, or indignant over free riders. But we will need to be smart about which tools we use to summon our better angels. Looking at the history of life on our planet, one lesson we can learn is that the groups of today might be the organisms of tomorrow, an invisible hand selecting us all for a higher calling. Looking at human history, we perceive that fate is more than biology. At least for the moment, we have ourselves alone to help us be good.

Oren Harman is chair of the graduate program in science, technology, and society at Bar-Ilan University, in Israel, and the author of The Price of Altruism: George Prince and the Search for the Origins of Kindness (W.W. Norton, 2010).

Books Discussed in This Essay

Does Altruism Exist? Culture, Genes, and the Welfare of Others

by David Sloan Wilson

(Yale University Press, 2015)

The Altruistic Brain: How We Are Naturally Good

by Donald W. Pfaff

(Oxford University Press, 2014)

The Paradox of Generosity

by Christian Smith and Hilary Davidson

(Oxford, 2014)