Survival of the Friendliest

Survival of the Friendliest Plot Summary

Introduction

In 1971, seventeen years after Brown v. Board of Education declared school segregation unconstitutional, fifth-grader Carlos was being mercilessly teased by his classmates for his stammer. His teacher, not wanting to put him on the spot, stopped calling on him, inadvertently isolating him further. When psychologist Elliot Aronson observed this classroom, he identified a fundamental problem: the traditional classroom structure created constant competition among students for their teacher's approval. Aronson introduced the "jigsaw method," where each child in a group had a piece of knowledge to contribute. Carlos was put in charge of teaching about Joseph Pulitzer's middle years. When he stammered, his group realized they needed Carlos to succeed themselves. After just six weeks, children in jigsaw groups liked each other regardless of race, enjoyed school more, and showed improved self-esteem and empathy. This simple shift toward cooperation mirrors a profound truth about human evolution: cooperation, not aggression, has been the key to our survival as a species. While the myth of "survival of the fittest" suggests that being bigger, stronger, and meaner leads to evolutionary success, the reality is that friendliness and cooperation have driven human advancement. This paradox—how friendliness and our capacity for cruelty coexist—forms the central question this exploration aims to answer.

Chapter 1: Origins of Human Friendliness: The Self-Domestication Hypothesis

Between 200,000 and 300,000 years ago, Homo sapiens was just one of at least five human species sharing the planet. Some of these other humans had brains as large as or larger than our own. If brain size was the main requirement for evolutionary success, these other humans should have thrived. Instead, their populations remained sparse, their technology limited, and eventually, they all went extinct. Even our own species showed little promise initially. For the first 150,000 years of our existence, there was a strange gap between our physical appearance and our cultural development. Though we possessed the anatomical features that distinguished us from other humans, our technology remained basic—we used the same hand ax that Homo erectus had invented a million and a half years earlier. In fact, genetic evidence suggests our population may have dwindled to near extinction around 100,000 years ago. Then, around 50,000 years ago, something remarkable happened. We began developing sophisticated tools like projectile weapons that could kill from a distance. We created art, jewelry, and complex living arrangements. We spread rapidly across Eurasia and possibly reached Australia within a few thousand years. What changed? The self-domestication hypothesis provides an answer: we evolved to become friendlier with one another, which enabled unprecedented cooperation and communication. This process mirrors what happened when wolves evolved into dogs. Just as ancient wolves who were calmer around humans gained access to new food sources and thrived, early humans who were less aggressive toward strangers could form larger groups, share knowledge, and create more sophisticated technologies. This wasn't the result of bigger brains—our brains had reached modern size long before our cultural explosion. Instead, it was a change in our social behavior. By becoming more tolerant of one another, we could live in larger groups and share innovations more effectively. The self-domestication hypothesis suggests that natural selection favored humans with reduced reactive aggression. Those who could manage their fear and anger around strangers gained evolutionary advantages. This selection pressure caused changes not just in our behavior but in our physical appearance, with more feminine-looking faces developing over time, similar to the physical changes seen in other domesticated animals.

Chapter 2: Cooperation vs. Aggression: The Evolutionary Advantage of Kindness

For generations, popular understanding of evolution has been dominated by a simplistic notion of "survival of the fittest," suggesting that the bigger, stronger, and more aggressive individuals would inevitably prevail. Darwin himself, however, observed that "those communities which included the greatest number of the most sympathetic members would flourish best and rear the greatest number of offspring." Modern biologists have confirmed that aggression often carries significant costs, including stress, physical injury, and reduced reproduction. From the microscopic level of mitochondria joining larger cells millions of years ago to the complex social arrangements of ants forming superorganisms of up to 50 million individuals, cooperation has repeatedly proven to be a winning evolutionary strategy. Human cooperation, however, has reached unprecedented levels of sophistication. While other primates like chimpanzees can cooperate in limited contexts, they struggle to communicate cooperatively—a skill that emerges spontaneously in human infants before they can even walk or talk. By around nine months of age, human babies begin to point to share attention with others—a seemingly simple gesture that requires sophisticated mind-reading abilities. This capacity to understand others' intentions forms the foundation of what psychologists call "theory of mind," our ability to understand that others have thoughts, beliefs, and emotions that may differ from our own. Theory of mind allows us to engage in complex cooperation and communication, making it crucial to almost every problem we face. What makes humans unique is not just our capacity for cooperation but the scale at which we do it. Hunter-gatherer societies evolved mechanisms to prevent individuals from monopolizing resources, creating egalitarian groups where food was shared and power was distributed. This social arrangement allowed our ancestors to outcompete other human species not through individual strength but through collective intelligence and shared innovation. The archaeological record shows that around 80,000 years ago, humans began showing physical changes associated with self-domestication—smaller brow ridges, shorter faces, and eventually smaller, more globular skulls. These changes weren't selected for directly but emerged as side effects of selection for reduced reactive aggression. Just as Belyaev's famous fox domestication experiment showed that selecting for tameness produced unexpected physical changes like floppy ears and spotted coats, selection for human friendliness reshaped our faces and bodies.

Chapter 3: The Bonobo Connection: Lessons from Our Peaceful Cousins

Bonobos and chimpanzees, our two closest living primate relatives, shared a common ancestor around a million years ago. These two species offer a fascinating natural experiment in evolution—while genetically similar, they've developed dramatically different social systems. Where chimpanzees form hierarchical, male-dominated groups marked by lethal aggression, bonobos have evolved a remarkably peaceful society. Male chimpanzees regularly patrol their territorial borders, and when they encounter males from neighboring groups, they often attack with lethal force. Researchers have found that the homicide rate among chimpanzees is similar to that of hunter-gatherer humans. Female chimpanzees also maintain strict hierarchies, with high-ranking females getting access to the best food resources. When females reach puberty and attempt to join new groups, they're often severely beaten by resident females. Bonobos, by contrast, have never been observed killing each other in either captivity or the wild. Male bonobos don't form gangs to patrol borders or commit violence against neighboring groups. In fact, neighboring groups of bonobos are just as likely to mingle peacefully, share food, and interact amicably as they are to show any hostility. The females form strong bonds with each other and work together to control aggressive males. This peaceful society appears to have evolved because bonobos had more abundant and predictable food sources south of the Congo River, where they live. With less competition for resources, female bonobos could afford to form alliances. These female coalitions could effectively control male aggression, leading to selection for less aggressive males. Over time, the entire species became more friendly and cooperative. The physical changes associated with this behavioral shift mirror those seen in domesticated animals. Compared to chimpanzees, bonobos have smaller faces, more crowded teeth, and some individuals lack pigmentation in their lips and tail tufts. Male bonobos' brains are approximately 20% smaller than those of male chimpanzees. These changes are remarkably similar to those seen in domesticated foxes, dogs, and other animals selected for tameness. When researchers tested bonobos and chimpanzees on cooperative tasks, they found that bonobos outperformed chimpanzees despite having less training. Even when food was placed in a single pile that required sharing, bonobos continued to cooperate while chimpanzee cooperation broke down. This suggests that bonobos, like humans, have undergone a process of self-domestication that enhanced their ability to work together peacefully. The bonobo example demonstrates that self-domestication can occur through natural selection without human intervention, providing a valuable model for understanding our own evolution toward greater friendliness and cooperation.

Chapter 4: The Neural Basis: How Domestication Rewired Our Brains

The cognitive differences between humans and our closest relatives emerge early in development. By nine months of age, human infants begin pointing to share attention with others—a seemingly simple gesture that reveals sophisticated mind-reading abilities. This early-emerging "theory of mind" allows humans to understand others' intentions, beliefs, and emotions in ways that even our closest primate relatives cannot fully match. When researchers directly compared human, chimpanzee, and bonobo infants on various cognitive tasks over three years, they found that two-year-old human babies already showed more social skill than the nonhuman apes, despite having similar abilities in nonsocial domains like understanding physics or using tools. By age four, human children had outstripped the other ape infants on every task. The same toddlers who struggle to avoid spilling their drinks have already developed theories about how other minds work. This accelerated social development appears linked to changes in brain structure that emerged uniquely in Homo sapiens. Unlike other humans like Neanderthals, who had low, flat foreheads and thick skulls, our species evolved balloon-shaped heads to accommodate our uniquely shaped brains. The top and back of our brains—the parietal regions that house critical nodes of our theory of mind network—underwent particularly rapid growth after birth, creating our distinctive globular head shape. Remarkably, these physical changes appear to be linked to alterations in brain chemistry associated with domestication. In Belyaev's famous fox domestication experiment, one of the first changes observed in foxes selected for tameness was increased serotonin levels in their brains. Serotonin not only influences behavior, making animals less reactive and more sociable, but also affects skull and brain development. Human infants who were exposed to higher serotonin levels during development tend to develop more globular skulls—exactly the pattern seen in our species compared to other humans. Another striking change in human evolution was the development of white sclera—the whites of our eyes. We are the only primate with white sclera, which makes our eye direction highly visible to others. From birth, human infants prefer eyes with white sclera, and by four months, they can use the shape of others' eye whites to understand emotions. This adaptation promotes cooperative communication and appears linked to increased oxytocin, the hormone associated with social bonding. These neurobiological changes didn't just make us friendlier—they rewired our brains for unprecedented social learning and cultural transmission. While other animals shut down brain growth soon after birth, humans maintain fetal brain growth rates for two years after birth, allowing our neural circuits to be shaped by social interaction. This extended developmental period creates a feedback loop: our early-emerging social skills allow us to connect with caregivers who provide the protection we need while our brains continue developing, which in turn enhances our social abilities. Self-domestication thus created a unique combination of neural adaptations that made humans exceptionally skilled at reading one another's intentions, sharing knowledge across generations, and building upon innovations collectively—the foundation for cultural evolution that ultimately gave us language, technology, and civilization itself.

Chapter 5: The Dark Side: Dehumanization and Intergroup Conflict

The same neural mechanisms that enable our extraordinary capacity for empathy and cooperation also contain the seeds of our darkest behaviors. When we perceive members of another group as threatening, our brain's theory of mind network—the very circuitry that allows us to understand others' thoughts and feelings—can become less active. This dampening of empathy allows us to "dehumanize" others, viewing them as less than fully human and therefore outside the moral protections we afford to members of our own group. In 2016, researchers asked Americans to rate how "evolved" they considered various groups using an image depicting the "Ascent of Man"—a misrepresentation of evolution showing a linear progression from ape to human. Disturbingly, they found that participants often rated members of other groups as less than fully human. Muslims were rated 10 points below fully human, and this dehumanization directly predicted support for policies like torture and drone strikes. Similar patterns appeared when measuring dehumanization between Palestinians and Israelis, Hungarians and Roma, and across many other contexts. What makes this phenomenon particularly troubling is its universality. In study after study, researchers have found that dehumanization exists across cultures, ideologies, and demographic groups. When white Americans were asked how evolved they considered black Americans to be, a significant portion rated them as less evolved than white people. This pattern appeared among Democrats and Republicans, conservatives and liberals, men and women, high-income and low-income individuals, Southern and non-Southern respondents, young and old. Even more concerning is the finding that dehumanization increases dramatically when people feel threatened. After terrorist attacks, rates of dehumanization toward Muslims spiked by almost 50%. The most powerful predictor of whether one group would dehumanize another was the perception that they themselves were being dehumanized—creating dangerous cycles of reciprocal dehumanization that can escalate into violence. This dark side of human psychology appears directly linked to our evolutionary history. The same hormone—oxytocin—that promotes bonding within groups can also increase hostility toward outsiders. When researchers administered oxytocin to participants and presented them with moral dilemmas involving members of their own group versus outsiders, they became 25% less likely to sacrifice members of their own group. The hormone that makes us loving toward family and friends can make us callous toward those perceived as threats. Understanding this connection between our capacity for love and our capacity for cruelty is essential for addressing intergroup conflict. While our tendency to form exclusive social bonds evolved because it enhanced survival through cooperation, in the modern world where different groups must coexist, this same tendency can lead to devastating conflict when directed against perceived outsiders.

Chapter 6: Creating Peace: Contact, Democracy, and the Path Forward

After World War II, many scholars assumed that contact between different groups would ignite conflict rather than resolve it. They believed people felt safer in communities where others spoke the same language and shared the same customs. This reasoning was used for years to justify segregation, both by powerful majorities and disadvantaged minorities. W.E.B. Du Bois argued that "a separate Negro school, where children are treated like human beings, trained by teachers of their own race, who know what it means to be black, would be infinitely better than making our boys and girls doormats." However, research since then has consistently shown that contact between groups is the most reliable way to reduce conflict. When the U.S. Army recruited 2,500 black soldiers to fight in the Battle of the Bulge, even the more intolerant white soldiers from the South who fought alongside them developed more positive attitudes. College students randomly assigned to roommates of different races reported more comfort in mixed-race interactions, more diverse friendships, and greater tolerance toward interracial dating years after living together. Contact works because it reduces the perceived threat between groups, allowing people to empathize with one another. Schools, universities, integrated housing, and military service create opportunities for sustained friendly contact that can transform attitudes. Even imagining positive contact with members of dehumanized groups can increase empathy, and fictional portrayals in literature and media can have similar effects. Harriet Beecher Stowe's "Uncle Tom's Cabin" was a turning point in the abolitionist movement, while a Rwandan soap opera helped reduce prejudice between Hutus and Tutsis after the genocide. Most powerfully, contact appears to have the greatest impact on the most intolerant individuals. People high in social dominance orientation (who believe some groups are inherently superior to others) and right-wing authoritarianism (who favor strict conformity and traditional values) show the most dramatic positive changes after extended contact with members of other groups. This suggests that the people most prone to dehumanize others are also the most receptive to the humanizing effects of face-to-face interaction. Democracy provides a crucial framework for facilitating this contact. Unlike authoritarian systems that often exploit group differences to maintain power, democracies are designed to protect minority rights and promote compromise between different interests. As Madison wrote in the Federalist Papers, "So strong is this propensity of mankind to fall into mutual animosities, that where no substantial occasion presents itself, the most frivolous and fanciful distinctions have been sufficient to kindle their unfriendly passions." The American founders understood the dangers of dehumanization and designed a system with checks and balances specifically to prevent the "tyranny of the majority." In our increasingly urban world, architecture and urban planning also play important roles in either promoting or hindering contact. Cities that feature mid-rise buildings, mixed-income housing, walkable neighborhoods, and shared public spaces create opportunities for people from different backgrounds to interact naturally. These structural elements can help break down barriers between groups and cultivate the friendliness that has been our species' greatest evolutionary advantage.

Summary

The story of human evolution is not simply about bigger brains or better tools, but about the extraordinary power of friendliness. Through a process scientists call self-domestication, our species evolved to be less reactively aggressive and more tolerant of strangers, enabling unprecedented cooperation. This evolutionary shift can be seen in physical changes—more feminine faces, white sclera in our eyes, and more globular skulls—that mirror those observed in other domesticated animals. These changes weren't the result of intentional breeding but emerged through natural selection as individuals who could cooperate with more people gained survival and reproductive advantages. Yet this same capacity for friendliness contains a paradox. When we perceive others as threatening our group, we can dehumanize them—literally turning off the parts of our brain responsible for empathy and moral consideration. This universal human tendency transcends politics, culture, and education levels, emerging whenever we feel our group identity is under threat. The solution lies in understanding that contact between groups reduces this threat perception, allowing our natural capacity for empathy to flourish. By designing our societies, cities, and institutions to facilitate positive contact between different groups, we can harness the better angels of our nature—the friendliness that made us human in the first place—to build a more peaceful world. What saved our species from extinction tens of thousands of years ago remains our greatest hope for addressing today's polarization and conflict.

About Author

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Brian Hare

Brian Hare is Professor of Evolutionary Anthropology at Duke University, where he founded the Duke Canine Cognition Center. His research on 'dognition' has been published in the leading journals. With his wife Vanessa Woods, he cofounded the new dog intelligence testing and training company Canines Inc. To find out more, visit the Dognition website.

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