How Did Altruism Evolve?

We often talk about evolution in terms of competition, as the survival of the fittest. But if it is, then where did the widespread (and widely admired) impulse to help others even at great cost to ourselves come from? In this episode, Stephanie Preston, a professor of psychology and head of the Ecological Neuroscience Lab at the University of Michigan, talks about the evolutionary, neurological and behavioral foundations for altruism with our new co-host, the astrophysicist and author Janna Levin.

Listen on Apple Podcasts, Spotify, Google Podcasts, TuneIn or your favorite podcasting app, or you can stream it from Quanta.

Transcript

JANNA LEVIN: If you are listening to this podcast, chances are you’re a human. And chances are at some point, at least once in your life, you’ve acted in complete and total disregard for yourself, putting the needs of others above all else. But why?

We often talk about evolution in terms of competition and survival of the fittest. Why would someone give to charity or donate blood or run into a burning building to save another? What evolutionary purpose does this selflessness serve? And is there a biology of altruism?

I’m Janna Levin, and this is “The Joy of Why,” a podcast from Quanta Magazine where I take turns with my co-host, Steve Strogatz, exploring some of the most exciting research in math and science today.

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In this episode, we’re speaking to Stephanie Preston about the biological basis of altruism and why you should care. Stephanie is a professor of psychology and head of the Ecological Neuroscience Lab at the University of Michigan. She investigates the evolutionary reasons for emotion, empathy and decision-making across species.

In 2002, she and famed primatologist Frans de Waal authored a seminal work on the empathy of animals, and in 2022 she authored a book titled The Altruistic Urge: Why We’re Driven to Help Others. Stephanie, it’s so great to have you with us. Welcome.

STEPHANIE PRESTON: Great. Thanks for having me.

LEVIN: We’re excited to talk about this topic. I think we’re all probably familiar with the notion of altruism on some level, but how do you define it as a scientist?

PRESTON: Yeah. I define it as aid to another at a current cost to yourself. And it’s really important to include that current cost, because anything that’s evolutionarily adaptive has some benefit in the long run, whether you realize it or not.

LEVIN: Now, do you distinguish altruism from selflessness, empathy, morality? Are these just related terms?

PRESTON: They’re definitely all interrelated, but they do have slightly different meanings and ways in which we need to understand them. Empathy is more like sharing in the emotions of others. It can be at a conscious or not conscious level where you catch somebody else’s emotions when you’re paying attention to how they feel.

That can cause you to want to be altruistic. If you’re observing somebody who’s distressed, it can make you feel a little distressed, or activate the part of your brain that processes felt distress, whether you are aware of that or not. And that motivates you then to do something about their state, to alleviate that negative affect.

So empathy can lead to altruism, but there’s a lot of times when people do something for another even without having crossed through that empathy. And that’s what The Altruistic Urge is about. It’s how we evolved this caregiving urge in situations that are highly similar to a helpless offspring, in ways that are adaptive and contribute to our reproductive success.

LEVIN: And would you distinguish that from selflessness, or would you say those are rather interchangeable?

PRESTON: It’s a word I prefer not to use because people want to know, is it truly selfless? Because some people want to spend a lot of time talking about, is there any such thing as true altruism? And by that they mean “truly selfless,” like you have no skin in the game, it can’t help you. It maybe even hurt yourself and only benefited the other individual.

But if you think about a biological lens, everything has some sort of adaptive value in the near-term, in the long-term. And rarely are there times where we truly do something for the other, and die trying. But usually there’s some benefit. You share with me; I share with you again later. I help you; it makes me feel good. That’s part of how the brain and body evolved to help. It does feel good, and that shouldn’t be a bad thing. That’s a really awesome design in the nervous system that helps us all be better people and feel good by giving up something for another.

So I wouldn’t want to denigrate that. But sometimes if people talk about selflessness, they don’t even want you to feel good. Isn’t it a good thing that our society values philanthropy in that way? So, I think these are all positives, whereas somebody who worries about selflessness sees them as negatives.

LEVIN: Now, do you think that as a species, we are indeed altruistic?

PRESTON: Oh, for sure. Yeah. In tiny ways to huge ways, every day. I think we’re part of a social species, which depends upon altruism to help us stay coordinated and bring us all the benefits that we need to make it through this life.

LEVIN: Are we unique in displaying altruism among species? Is this something we share with other mammals? Or even other species that are not mammals?

PRESTON: Yeah, it’s not unique at all. In the book and in my work with Frans de Waal, we have talked a lot about this. What is unique, perhaps, is the way in which humans want to sit around and think about it, or they could like cogitate for a really long time about the pros and cons. That’s not something another species is probably doing.

But my book, The Altruistic Urge, is about this way in which we have in common this neurobiological system with other species, especially other mammals, that evolved to take care of offspring. You see somebody vulnerable; they need immediate care; it’s aid you know how to give. And especially if you’re bonded with them or familiar with them, you just get this instinct to jump in and help.

An instinctual form of altruism, for sure we share with other species. And they even show altruism in non-mammals. You can even see altruism in ants. We’re not sure yet if the mechanism in the brain is the same. So, it’s interesting to contemplate across the animal kingdom.

LEVIN: Yeah, I remember a story of a worker ant having to feed a soldier ant who biologically evolved to be incapable of feeding themselves.

PRESTON: Yeah, their species is dependent on this kind of aid in a really strict hierarchical structure. And it makes sense in those species — like, also in bees — because you are actually more related to the other individuals. So, it’s consistently shown that inclusive fitness, which is what they call when we share genes, makes altruism sensible and adaptive. Because if I help you and we have shared genes, I’m helping the genes that we have in common, and therefore the behavior persists in the gene line. And so that’s true of people as well as bees and ants.

LEVIN: Can you explain the phenomenon of offspring retrieval and how that relates to your work?

PRESTON: Yeah. I did some work early in my career in monogamous voles, which are species that mate and then they take care of their young together. The females and the males stay bonded with the same partner. And so, people were interested in the neurobiology of this. And it turns out that the act of mating releases this sort of cascade of hormones and changes in the brain. Pregnancy also changes the hormones in your brain and in your body.

And these hormones prime us to want to protect and care for the individuals in our family. So the males who are mated protect the den from intruders. And the females are retrieving the pups that they’ve given birth to when they become isolated, or they hear these high-pitched sounds of distress that we might not even hear, but they can hear it. And so there’s this instinctual retrieval response. And it’s not just in pregnant females. They can get males or females who haven’t mated to do the retrieval response.

LEVIN: Now, you mentioned this cascade of hormones. Is there a permanent neurological change in the brain as a result of these hormones, or is it temporary during the time that the hormones are being elicited?

PRESTON: It’s probably both. For example, in the rodents, they demonstrate this super intense need to retrieve the pups that almost can’t habituate. They’ll do it over and over again for hours, just because it’s unlocked by those hormones and it’s so important in that phase of development. So that really intense response can wane over time. They have really interesting studies where a female who’s given birth is faced with two chambers. One has cocaine and one has the pup, and they will choose the pup.

LEVIN: (laughing) Are we sure they like cocaine?

PRESTON: We are sure they like cocaine, actually, because they do studies just on that for addiction. But they have other studies in humans. Human fathers don’t go through the birthing process, but they also change from experience. So, they do experiments where you hear a baby cry, or you have to respond to distress. And males who are fathers respond more empathically in the body and in behavior than ones that are not fathers.

Once you’ve had these experiences, you can’t unlearn that. And your brain has gotten used to doing these behaviors, when they’re appropriate, how to do them correctly. So you don’t always have to rely on the instinct once you have a system in place to know what to do.

LEVIN: Some of this sounds contradictory to the classical notion of evolutionary biology where everything is just about selfish survival. I think you’ve explained well why there would be evolutionary pressure in the longer term to have this kind of evolution to be altruistic and protect the young. Do you see a distinction between the kind of old-guard ideas about selfishness in evolutionary theory and yours?

PRESTON: Yeah, I think they have known for a long time that things like being related to the individual makes altruism sensible and that can occur across species, or that it can be sensible to give to one when you can receive a gift back. They call that reciprocity. “Do unto others as you would have them do unto you” is something that works in the animal kingdom and in people.

But I think what’s unique here is that these features are coming together in a way that promotes behaviors toward total strangers. Let’s take an example of a heroic rescue. If you see a burning building, or somebody falls in rushing waters, it takes great risk to your personal fitness to get involved, and we call them heroes almost specifically because they helped a stranger.

LEVIN: And we are amazed by those stories. We are amazed.

PRESTON: Exactly. And that’s why they’re remarkable. We have these beliefs about who and when we should intervene, and a lot of the people who get the Carnegie Medal of Heroism actually die during the process. But you have this built-in system, which is: They’re vulnerable; they cannot help themselves; the help has to come immediately; and I know what to do. I predict that I can do this.

Your brain is really good at making predictions about motor behavior. Is your act going to reach them in time? Are you strong enough to pick them up? Will you be able to get out before the fire reaches catastrophic levels? So, your brain makes those predictions very quickly, and it does not require all this conscious processing. So, a lot of human researchers want to think we can only do altruism because we’re so intelligent. But I think we share this neural system and its capacity with other species. And it doesn’t have to be consciously cogitated.

LEVIN: Now, that’s so interesting. You have talked about how the urge for altruism might be a part of our older brain in some sense, our prehuman brain. Can you talk specifically about which parts of the brain seem to be involved?

PRESTON: Sure. There are certain areas of the brain that we know are involved in this transition to caregiving. For example, the striatum, which is rich with dopamine receptors and with oxytocin receptors, is influenced by the process of caring for young and mating — and cocaine, by the way. Things that — you want to approach them because you predict that it’ll be rewarding.

You approach the offspring because you predict it will make you feel good, or you give to somebody because you predict it will make you feel good. And you don’t actually need conscious awareness to do that. If they do brain imaging studies with people and you’re allowed to do something more abstract — donate money to a cause — you still have involvement of this same brain area.

There’s commonality across species in the involvement of a brain area like the striatum. And also the hypothalamus is like a tiny old structure that is involved with the hormonal shifts during these periods. And of course your cortex can get involved. You can have prefrontal activity that we’re usually consciously aware of, but it doesn’t have to. I think that’s the key.

LEVIN: I suppose you can’t run a brain scan while somebody’s running into a burning building, but can you tell if there’s a way to deduce if these kinds of areas are in conflict or how one wins out over the other?

PRESTON: Yeah, that’s an awesome question. The amygdala is actually a pivot point in this approach-versus-avoid system. So, in the rodents, the amygdala will get activated and then it will produce avoidance responses like fear and running away if you don’t have familiarity and the hormones on board and the conditions aren’t right. And if you’re scared of the rushing water because you can’t swim, your amygdala is going to be shunting into the avoidance system, and you’re not going to want to jump in.

But if the conditions are right and you have the hormones on board or you’re bonded with the individual, you feel safe, you think you can do the act in time, then the amygdala projects to different areas that then produce the approach motivation. So, the amygdala is involved in either case. It’s not involved only during fear. It’s also involved during this sort of emotional approach system.

LEVIN: Interesting. I remember hearing you talk about the subway hero where a young man had an epileptic seizure and fell on the subway tracks in New York City. I should let you tell the rest of the story. It’s so compelling.

PRESTON: Yeah, it is like a really awesome story. The young man had a seizure and so everybody on the platform had witnessed that, they knew he was in a medical crisis. So then the young man falls into the tracks, and Wesley Autrey is the man who is standing there with his two young daughters and the train is coming and he makes a split-second decision that easily could have ended his life.

He jumped in and, like we’re saying, his brain can predict that there’s no time to pull the man out even if he were strong enough to do it, because the train is coming too close. What he does is he flattens the young man in between the tracks and lays on top of him and tells him, “It’s going to be all right,” and then holds him down. And then the train passes over them, leaving only like a centimeter to spare.

So he made a very quick but also very accurate decision that they would fit under the train, which they think might be related to his experience in tight spaces. He had been on submarines and in union construction work. But, from a rational perspective, it was a terrible idea to jump in, and he easily could have ended his life.

He was with his two young daughters, so his inclusive fitness would have, if anything, gotten worse, not better. But this motor system actually made a very accurate prediction, and those are the preconditions that are really similar to a helpless offspring because the young man really couldn’t help himself in that situation and everybody knew it. It wasn’t like a judgment call, the way we might make a judgment call with somebody who we think is responsible for their plight, and then we’re not sure if we want to help them. It’s immediate, and we’re sure they need our help, and we think we can do it.

LEVIN: So there’s a great example of that physical motor preparation you were discussing. You were saying it might not make sense from a typical evolutionary perspective because his children were there, that his defense of them would be larger, his own survival being important for them. But at the same time, it does anecdotally seem to relate to the idea of all these hormones kicking in, a parental hormone or the hormones of caregiving.

It’s also interesting that even though other people didn’t do it, everyone was horrified. So there’s something about the human brain that makes us care, even if we can’t act.

PRESTON: Right, and that’s that empathy component. The way our brains process other people’s emotions and pain relies on activating our own brain areas where we feel emotions and pain. And so, whether we like it or not, it’s difficult for us to observe somebody else in pain. People maybe have gotten pretty good at changing where they direct their attention, looking away, justifying themselves after the fact if they don’t want to help or can’t get involved. But it’s really hard if you’re forced to watch somebody in pain or get hurt.

LEVIN: We’ll be right back.

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LEVIN: Welcome back to “The Joy of Why.”

Now, you’ve also discussed things like the in-group and out-group effect, which is relevant to how much pain people experience for someone else. Could you pick that apart for us a little bit, the in-group/out-group effect?

PRESTON: Yeah. So, for example, you can put somebody in a brain scanner and then, let’s say you prick your finger with a needle, and it hurts. These regions, like the anterior cingulate and the anterior insula, are regions that represent that feeling of pain, the subjective negative emotion of it all. And those are going to light up when you’re in pain. But then if you observe, let’s say in a video, or somebody else’s finger getting pricked with a needle, then those areas also light up. So this is like proof that we’re sharing in the emotions of other people, because we’re using the same brain areas that we use to feel pain to process other people’s pain.

But then, the scientists did interesting things where they show you the pain of somebody similar to you or somebody different from you. One of the early studies had faces that were Chinese versus non-Chinese faces, or they’ve done — they’re from your soccer team or they’re from the opposing soccer team. You can do an in-group/out-group in many different ways, but as long as you highlight that feature in the moment, people actually have a significantly lower shared pain response in the brain to the out-group.

And so it’s not just like we decide not to help them because they’re from the other camp. It’s actually like your brain is not responding to the same degree.

And so there’s a lot of forces in the world today, in politics, that rely on these in-group biases. And so if we want to reduce some of those, then we have to figure out the cause of this, and my empathy model is focused on the attention. We don’t want to pay as much attention to somebody who’s not from our in-group and especially if we don’t want to be involved in the pain.

LEVIN: Do you think there’s any merit to the idea that we can be inoculated against a sort of empathetic pain by a lot of exposure to violence, even if it’s something as trivial as exposed to violence on TV?

PRESTON: Definitely. Just as one example, they’ve done research studies where you take somebody who’s an anesthesiologist, who gives pain injections for a living, and you have them watch videos where somebody else gets a needle and they have a much-reduced response. Because not only have they seen it many times, but also, they know it has a positive goal.

So we know that your brain can habituate with experience, and also it changes depending on the goal of the situation. If they’re highlighting the fact that you’re enemies during the context, you’re going to have a much bigger response, but if they’re highlighting, you and I are different, but we have this thing in common that we share, then your response is going to be more empathic. So we need to, I think, work on the common humanity that we all share.

LEVIN: Now, do you think that there are things we can do as a culture, as a society, to augment the potential for altruism, a set of guiding principles or a philosophy that would make our society permanently better?

PRESTON: Yeah, that’s an awesome question. Ultimately, we’re a global society, whether we want to think so or not. We’re all dependent on one another for goods and services and energy and food. And those individuals suffering on the other side of the world seem distant. And we don’t know much about them. We don’t know much about their struggle. We don’t know much about what their day-to-day lives are like. We just hear that there’s a problem.

But your brain evolved for immediacy. Your brain evolved for the person to be right in front of you, and you can see the suffering, and you feel that you can do something to help.

So I think, in order for this to get better, we have to have more exposure to people from other cultures, and how are they similar to us, and how are we interdependent in this global society, and what can we do to help that seems effective?

You don’t act unless you think you’re capable and it’s going to work, that’s something that your brain calculates very implicitly. And so, if somebody is asking you to donate to a cause and you think the situation’s hopeless, then you’re not going to be inspired to act. So, there have to be ways in which people can get involved that feel doable, that feel achievable.

LEVIN: Are there ways that we can scientifically actually test some of these theories on such a large scale?

PRESTON: There is already some research on this. They have the identifiable victim effect where, if you observe a single individual in crisis, you’re more likely to donate money than if it’s an abstract group. Or you’re more likely to donate money to groups that you have some affiliation with than ones that are unfamiliar to you. We know that people give more when they understand more about the situation, and a lot of research demonstrates that people feel self-efficacy and they’re more likely to act when they think it’s going to work.

And there’s a lot of research on the bystander effect, which is the inverse, that we don’t help — when we think we’re not the ones who are going to save the day, somebody else probably should do it, and I’m worried about what will happen if I respond. What I’m working on now is thinking of ways to use the narratives of people who are not like us to get at your emotional understanding of what it’s like to be in another person’s shoes.

LEVIN: And how is that work being executed, scientifically? Are you looking at the brain and hormones?

PRESTON: So, for example, there’s research showing that if you read a story of an out-group with a lot more detailed information, you’re more likely to empathize with their plight. In these political contexts, people’s defenses are up. If you go through the arts, you can go around the wall of defenses in ways that are interesting and palatable and feel safe. People still learn and their brains develop an understanding of the context of the other individuals, which is very important for understanding and empathizing with their plight and wanting to help.

LEVIN: Now, how do you think these studies on altruism and empathy can impact questions like morality, or even the justice system or the penal system?

PRESTON: Yeah. I think a lot of people study human morality, and most of that research is about conscious decisions that we make about, let’s say, where to allocate funding, or who to help, or whether to act or not act in a situation where somebody’s in peril. But to me, the most important thing is, without this basic machinery of feeling other people’s emotions and being interdependent and needing to help one another just for basic survival, I don’t think you can have morality.

Or it’s like morality with no teeth, right? It is what suffuses morality with meaning and importance in our lives. Some people, for example, they want to argue that empathy is bad, we would make better decisions and we would help more people if we didn’t use empathy.

But to me, it can’t be separated, because if you didn’t have the empathy to begin with, there would be no reason to care about how many people you helped. And I get how sometimes you need to step outside of that emotional pull and make rational choices about where international aid should go. But ultimately, we wouldn’t care to provide that aid in the first place if it weren’t for this basic building block that we do share with other species.

LEVIN: It makes me wonder, what would it look like if we continued to evolve as a more altruistic animal? What would we look like to that future, more altruistic species? And what would they look like to us? They might be appalled by what we think is moral and just.

PRESTON: That’s the interesting thing about history, right? Over the course of history, you can look back and say, “What we were doing then was appalling. We don’t do that now.” But then the future people are going to look at things we’re doing now and be appalled, and we consider them perfectly normal.

Somebody told me a story the other day about when the teachers in the public school were allowed to be physically aggressive when they were upset with the students. And we would be appalled if somebody slammed someone into a chalkboard now. They would be fired immediately. But back then, it was considered a smart play to keep the kids in line.

So history is telling us that what we think of as moral isn’t perfectly objective, and it’s influenced by culture and our beliefs that we learn from the people around us. But to me, the ideal in the future would be, you understand the common humanity of people all over the world, including other species and including nature itself. It helps if you think of nature as having inherent value. You help another country’s refugees if you think of them as having common humanity, and you could easily be in a situation just like that.

LEVIN: So, what is left in this study for altruism, from your point of view? What needs to be done?

PRESTON: I think we have some really basic applied problems that need to be solved in the real world. I think at this point we have a lot of expertise, and we know when people feel empathy, when they want to help. But we’re not seeing it in these times of crisis, globally, locally, in our own partisan politics in America.

What a utopian vision would be for me is where people are able finally to see the fellow humanity in people from all different cultures and races and situations, such that we want to feel interconnected and we want to understand that if we work together, everybody can survive.

And I even want that applied to animals and the natural environment. During a period of climate crisis, we need to be able to think about the environment itself as having inherent value. Even people’s happiness is higher when they spend time in nature, and people’s oxytocin is released when they look into the eyes of their dogs, and so they’re part of this interwoven system we know about but we’re not quite applying effectively yet, and that would be my dream for the future.

LEVIN: I think this idea of applying the altruism research to our understanding of how to inspire people to become more engaged in the climate crisis is really quite fascinating. So, how do we do that?

PRESTON: You’re exactly right. The climate crisis is almost like the perfect case study of what not to do if you want people to feel empathy-based altruism, because it’s abstract. It’s far away from us. The problem seems so huge. We don’t think we can do anything about it. We’re not sure what to do. We don’t quite understand how it works. Much of the time, people agree that the Earth is big and beautiful and permanent. It has this permanency and strength, and it cares for us. And that’s not going to inspire altruistic aid.

We have done studies where you separate people who tend to think of the Earth as vulnerable versus don’t naturally think of the Earth as vulnerable. And people do want to help more when they think of it as vulnerable. In the past, too much has just been focused on fear. And fear has its place. There’s new research showing that it can sometimes be effective to be fearful. But if you have this love and appreciation and you understand the vulnerability and the fragility and the beauty combined, that’s when people really want to act.

LEVIN: Fascinating. I have a question that we like to ask some of our guests, which is, what about your research brings you joy?

PRESTON: I actually love the original source of my research, which is learning about other species. I just think other species are infinitely interesting because there’s so much the same, but then there’ll be occasionally something really crazy that you learn about a species, especially a non-mammal, that you didn’t know, or that really makes you think again about all the possible ways that nervous systems can produce behavior.

Like ants: They can free a trapped ant from under a piece of fishing wire. And they will work really hard to free this trapped ant. They’re not just doing some rote motor behavior. It’s like they walk by, their friend is under this piece of wire, and they work hard until they can get it out. Rats will do the same thing in cages. And hopefully, people will do that in a situation where they feel like there’s something they can do about it.

So I’m really interested in the commonalities in the brain itself. And so I love learning more and more about that. Because wherever you look, there’s same and there’s also a little different, right? That’s why we are called the Ecological Neuroscience Lab, because a brain in another species has basically all the same parts. But then there are always small alterations in the genetic code or the specific receptors or the receptor locations that tweak the behavior to be adaptive for that species’ environment. The way nature is so ingenious really can fascinate me.

LEVIN: Science is fun to do.

PRESTON: From my chair, yes, it is. It feels that way.

LEVIN: We’ve been speaking with Stephanie Preston about the evolutionary, neurological and behavioral basis of altruism. Stephanie, thank you so much for joining us today.

PRESTON: Thanks for having me. It’s been such a pleasure.

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LEVIN: “The Joy of Why” is a podcast from Quanta Magazine, an editorially independent publication supported by the Simons Foundation. Funding decisions by the Simons Foundation have no influence on the selection of topics, guests or other editorial decisions in this podcast or in Quanta Magazine.

“The Joy of Why” is produced by PRX Productions. The production team is Caitlin Faulds, Livia Brock, Genevieve Sponsler and Merritt Jacob. The executive producer of PRX Productions is Jocelyn Gonzales. Morgan Church and Edwin Ochoa provided additional assistance. From Quanta Magazine, John Rennie and Thomas Lin provided editorial guidance, with support from Matt Carlstrom, Samuel Velasco, Nona Griffin, Arleen Santana and Madison Goldberg.

Our theme music is from APM Music. Julian Lin came up with the podcast name. The episode art is by Peter Greenwood and our logo is by Jaki King and Kristina Armitage. Special thanks to the Columbia Journalism School and Burt Odom-Reed at the Cornell Broadcast Studios.

I’m your host, Janna Levin. If you have any questions or comments for us, please email us at [email protected]. Thanks for listening.