The key to understanding how humans evolved and why we are so different from other animals is to recognize that we are a cultural species. Probably over a million years ago, members of our evolutionary lineage began learning from each other in such a way that culture became cumulative. That is, hunting practices, tool-making skills, tracking know-how, and edible-plant knowledge began to improve and aggregate—by learning from others—so that one generation could build on and hone the skills and know-how gleaned from the previous generation. After several generations, this process produced a sufficiently large and complex toolkit of practices and techniques that individuals, relying only on their own ingenuity and personal experience, could not get anywhere close to figuring out over their lifetime.
Once these useful skills and practices began to accumulate and improve over generations, natural selection had to favor individuals who were better cultural learners, who could more effectively tap in to and use the ever-expanding body of adaptive information available. The newly produced products of this cultural evolution, such as fire, cooking, cutting tools, clothing, simple gestural languages, throwing spears, and water containers, became the sources of the main selective pressures that genetically shaped our minds and bodies. This interaction between culture and genes, or what I’ll call culture-gene coevolution, drove our species down a novel evolutionary pathway not observed elsewhere in nature, making us very different from other species—a new kind of animal.
Over our evolutionary history, norm violations such as ignoring a food taboo, botching a ritual, or failing to give one’s in-laws their due from one’s hunting successes meant reputational damage, gossip, and a consequent loss of marriage opportunities and allies. Repeated norm violations sometimes provoked ostracism or even execution at the hands of one’s community. Thus, cultural evolution initiated a process of self-domestication, driving genetic evolution to make us prosocial, docile, rule followers who expect a world governed by social norms monitored and enforced by communities.
We don’t have these tools, concepts, skills, and heuristics because our species is smart; we are smart because we have culturally evolved a vast repertoire of tools, concepts, skills, and heuristics. Culture makes us smart.
The three common explanations for our species’ ecological success are (1) generalized intelligence or mental processing power, (2) specialized mental abilities evolved for survival in the hunter-gatherer environments of our evolutionary past, and/or (3) cooperative instincts or social intelligence that permit high levels of cooperation. All of these explanatory efforts are elements in building a more complete understanding of human nature. However, as I’ll show, none of these approaches can explain our ecological dominance or our species’ uniqueness without first recognizing the intense reliance we have on a large body of locally adaptive, culturally transmitted information that no single individual, or even group, is smart enough to figure out in a lifetime.
Humans survive neither by our instinctual abilities to find food and shelter, nor by our individual capacities to improvise solutions “on the fly” to local environmental challenges. We can survive because, across generations, the selective processes of cultural evolution have assembled packages of cultural adaptations—including tools, practices, and techniques—that cannot be devised in a few years, even by a group of highly motivated and cooperative individuals. Moreover, the bearers of these cultural adaptations themselves often don’t understand much of how or why they work, beyond the understanding necessary for effectively using them.
HOW TO MAKE A CULTURAL SPECIES
We need to understand how populations generate cultural adaptations—the suites or packages of skills, beliefs, practices, motivations, and organizational forms that permit people to survive, and often thrive, in diverse and challenging environments. The process is—in some crucial sense—smarter than we are. Over generations, often outside of conscious awareness, individuals’ choices, learned preferences, lucky mistakes, and occasional insights aggregate to produce cultural adaptations. These often-complex packages contain subtle and implicit insights that impress modern engineers and scientists.
Rather than opposing “cultural” with “evolutionary” or “biological” explanations, researchers have now developed a rich body of work showing how natural selection, acting on genes, has shaped our psychology in a manner that generates nongenetic evolutionary processes capable of producing complex cultural adaptations. Culture, and cultural evolution, are then a consequence of genetically evolved psychological adaptations for learning from other people. That is, natural selection favored genes for building brains with abilities to learn from others. These learning abilities, when operating in populations and over time, can give rise to subtly adaptive behavioral repertoires, including those related to fancy tools and large bodies of knowledge about plants and animals. These emergent products arose initially as unintended consequences of the interaction of learning minds in populations, over time.
Evolutionary reasoning suggests that learners should use a wide range of cues to figure out whom to selectively pay attention to and learn from. Such cues allow them to target those people most likely to possess information that will increase the learner’s survival and reproduction. In weighting the importance of those they can potentially learn from (hereafter their models), individuals should combine cues related to the models’ health, happiness, skill, reliability, competence, success, age, and prestige, as well as correlated cues like displays of confidence or pride. These cues should be integrated with others related to self-similarity, such as sex, temperament, or ethnicity (cued by, e.g., language, dialect, or dress). Self-similarity cues help learners focus on those likely to possess cultural traits (e.g., practices or preferences) that will be useful to the learner in their future roles.
In experiments, undergraduates rely on success-biased learning when real money is on the line—when they are paid for correct answers or superior performance. In fact, the more challenging the problem or the greater the uncertainty, the more inclined people are to rely on cultural learning, as predicted by evolutionary models. This tells us something about when individuals will rely on cultural learning over their own direct experience or intuitions.
Prestige: By observing whom others watch, listen to, defer to, hang-around, and imitate, learners can more effectively figure out from whom to learn. Using these “prestige cues” allows learners to take advantage of the fact that other people also are seeking, and have obtained, insights about who in the local community is likely to possess useful, adaptive information. Once people have identified a person as worthy of learning from, perhaps because they’ve learned about their success, they necessarily need to be around them, watching, listening, and eliciting information through interaction. Since they are trying to obtain information, learners defer to their chosen models in conversation, often giving them “the floor.” And, of course, learners automatically and unconsciously imitate their chosen models, including by matching their speech patterns. Thus, we humans are sensitive to a set of ethological patterns (bodily postures or displays), including visual attention, “holding the floor,” deference in conversation, and vocal mimicry, as well as others. We use these prestige cues to help us rapidly zero in on whom to learn from. In essence, prestige cues represent a kind of second-order cultural learning in which we figure out who to learn from by inferring from the behavior of others who they think are worthy of learning from—that is, we culturally learn from whom to learn.
Self-Similarity: Automatically and unconsciously, people also use cues of self-similarity, like sex and ethnicity, to further hone and personalize their cultural learning. Self-similarity cues help learners acquire the skills, practices, beliefs, and motivations that are, or were in our evolutionary past, most likely to be suitable to them, their talents, or their probable roles later in life. For example, many anthropologists argue that the division of labor between males and females is hundreds of thousands of years old in our species’ lineage. If true, we should expect males to preferentially hang around, attend to, and learn from other males—and vice versa for females. This will result in novices learning the skills and expectations required for their likely roles later in life, as mothers, hunters, cooks, and weavers. Similarly, since individual differences, like height or personality, might influence one’s success in various endeavors, learners may preferentially attend to those whom they resemble along these dimensions.
Our cultural learning biases are why role models matter so much.
Why Care What Others Think? Conformist Transmission
Evolutionary models, which are built to mathematically capture the logic of natural selection, predict that learners ought to use what’s called conformist transmission to tackle a variety of learning problems. As long as individual learning, intuitions, direct experience, and other cultural learning mechanisms tend to produce adaptive practices, beliefs, and motivations, then conformist transmission can help learners aggregate the information that is distributed across a group. Thus, the wisdom of crowds is built into our psychology.
Individuals reliant on cultural adaptations often have little or no understanding of how or why they work, or even that they are “doing” anything adaptive.
The central argument in this book is that relatively early in our species’ evolutionary history, perhaps around the origins of our genus (Homo) about 2 million years ago, we first crossed this evolutionary Rubicon, at which point cultural evolution became the primary driver of our species’ genetic evolution. This interaction between cultural and genetic evolution generated a process that can be described as autocatalytic, meaning that it produces the fuel that propels it. Once cultural information began to accumulate and produce cultural adaptations, the main selection pressure on genes revolved around improving our psychological abilities to acquire, store, process, and organize the array of fitness-enhancing skills and practices that became increasingly available in the minds of the others in one’s group. As genetic evolution improved our brains and abilities for learning from others, cultural evolution spontaneously generated more and better cultural adaptations, which kept the pressure on for brains that were better at acquiring and storing this cultural information. This process will continue until halted by an external constraint.
Cultural evolution can shape our environments, and consequently, it can drive genetic evolution. In cases of recent culture-gene coevolution, in which the relevant genes have not spread to replace all or most competing genetic variants, we can isolate the causes and effects and sometimes even finger the specific genes being favored. This is important because some researchers have argued that culture could never be strong enough for long enough to drive genetic evolution. Recently, however, new mathematical models and mounting evidence from the human genome provide a clear, if only preliminary, answer. Not only has culture driven specific genes to high frequency in some populations in the last ten millennia, but in fact, sometimes cultural evolution can create selection pressures more powerful than seen elsewhere in nature. Sometimes, culture catalyzes and drives more rapid genetic evolution.
ON THE ORIGIN OF FAITH
Cultural evolution is often much smarter than we are. Operating over generations as individuals unconsciously attend to and learn from more successful, prestigious, and healthier members of their communities, this evolutionary process generates cultural adaptations. Though these complex repertoires appear well designed to meet local challenges, they are not primarily the products of individuals applying causal models, rational thinking, or cost-benefit analyses. Often, most or all of the people skilled in deploying such adaptive practices do not understand how or why they work, or even that they “do” anything at all. Such complex adaptations can emerge precisely because natural selection has favored individuals who often place their faith in cultural inheritance—in the accumulated wisdom implicit in the practices and beliefs derived from their forbearers—over their own intuitions and personal experiences.
Educated Westerners are trained their entire lives to think that behaviors must be underpinned by explicable and declarable reasons, so we are more likely to have them at the ready and feel more obligated to supply “good” reasons upon request. Saying “it’s our custom” is not considered a good reason. The pressure for an acceptable, clear, and explicit reason for doing things is merely a social norm common in Western populations, which creates the illusion (among Westerners) that humans generally do things based on explicit causal models and clear reasons. They often do not.
Note, if you are educated and Western, you might be thinking that my numerous examples of toxic plants and animals are merely special cases, because you might be under the impression that few plants need detoxification and that nature’s bounty is pure and safe. For many Westerners, “it’s natural” seems to mean “it’s good.” This view is wrong and comes from shopping in supermarkets and living in landscaped environments. Plants evolved toxins to deter animals, fungi, and bacteria from eating them. The list of “natural” foods that need processing to detoxify them goes on and on. Early potatoes were toxic, and the Andean peoples ate clay to neutralize the toxin. Even beans can be toxic without processing. By contrast with our species, other animals have far superior abilities to detoxify plants. Humans, however, lost these genetic adaptations and evolved a dependence on cultural know-how, just to eat.
Not only do people often not understand what their cultural practices are doing, but sometimes it may even be important that they don’t understand what their practices are doing or how they work. If people came to understand that bird augury or bone divination didn’t actually predict the future, the practice would probably be dropped or people would increasingly ignore ritual findings in favor of their own intuitions.
Crucial to making cultural adaptations like manioc, corn, or nardoo processing work is not only faithfully copying all the steps, but also sometimes actually avoiding putting much emphasis on causal understandings that one might build on the fly, on one’s own. Cropping seemingly unnecessary steps from one’s cultural repertoire can result in neurological disorders, paralysis, pellagra, reduced hunting success, pregnancy problems, and death. In a species with cumulative cultural evolution, but only in such a species, faith in one’s cultural inheritance often favors greater survival and reproduction.
Of course, people can, and do, attempt to break down complex procedures and protocols in order to understand the causal links between them and to engineer better versions. They also alter practices through experimentation, errors in learning, and idiosyncratic actions. Nevertheless, as a cultural species, we have an instinct to faithfully copy complex procedures, practices, beliefs, and motivations, including steps that may appear causally irrelevant, because cultural evolution has proved itself capable of constructing intricate and subtle cultural packages that are far better than we could individually construct in one lifetime. Often, people don’t even know what their practices are actually doing, or that they are “doing” anything. Spicy-food lovers in hot climates don’t know that using recipes involving garlic and chili peppers protect their families from meat-borne pathogens. They just culturally inherited the tastes and the recipes, and implicitly had faith in the wisdom accumulated by earlier generations.
An enormous amount of scientific causal understanding, for example, has developed in trying to explain existing technologies, like the steam engine, hot air balloon, or airplane. A device or technology often preexisted the development of any causal understanding, but by existing, such cultural products opened a window on the world that facilitated the development of an improved causal understanding. That is, for much of human history until recently, cumulative cultural evolution drove the emergence of deeper causal understandings much more than causal understanding drove cultural evolution.
PRESTIGE, DOMINANCE, AND MENOPAUSE
Once humans became good cultural learners, they needed to locate and learn from the best models. The best models are those who seem to possess the information most likely to be valuable to learners, now or later in their lives. To be effective, learners must hang around their chosen models for long periods and at crucial times. Learners also benefit if their models are willing to share nonobvious aspects of their practices, or at least not actively conceal the secrets of their success. As a consequence, humans reliably develop emotions and motivations to seek out particularly skilled, successful, and knowledgeable models and then are willing to pay deference to those models in order to gain their cooperation (pedagogy), or at least acquiescence, in cultural transmission. This deference can come in many forms, including giving assistance (e.g., helping with chores), gifts and favors (e.g., watching their children), as well as speaking well of them in public (thus broadcasting their prestige). Without some form of deference, prestigious individuals have little incentive to allow unrelated learners to be around them and would not be inclined to provide any preferential access to their skills, strategies, or know-how.
To understand prestige as a social phenomenon, it’s crucial to realize that it’s often difficult to figure out what precisely makes someone successful. In modern societies, the success of a star NBA basketball player might arise from his (1) intensive practice in the off-season, (2) sneaker preference, (3) sleep schedule, (4) pregame prayer, (5) special vitamins, or (6) taste for carrots. Any or all of these might increase his success. A naïve learner can’t tell all the causal links between an individual’s practices and his success. As a consequence, learners often copy their chosen models broadly across many domains. Of course, learners may place more weight on domains that for one reason or other seem more causally relevant to the model’s success. This copying often includes the model’s personal habits or styles as well as their goals and motivations, since these may be linked to their success. This “if in doubt, copy it” heuristic is one of the reasons why success in one domain converts to influence across a broad range of domains.
We humans also possess a dominance psychology, which was inherited from our primate ancestors and is thus much older than prestige. In both primates and humans, individuals attain dominance status when others fear them and believe they will use physical violence or other means of coercion if they do not receive deference in the form of appeasement displays and preferred access to mates and resources (e.g., foods). In these hierarchies, subordinates signal their acceptance of a lower rank with displays involving diminutive body positions, including narrowed shoulders and a downward gaze. Dominant individuals remind subordinates of who the boss is with expansive body positions, upright torsos, widely spread limbs, and broadened chests.
Lower-status individuals preferentially attend to (watch and listen to) and imitate prestigious individuals but not dominant ones. This attention and imitation is usually automatic and unconscious. It may also include bodily mimicry that serves two separate functions. First, mimicry can be an unconscious way of showing deference, of assenting to a person’s higher prestige. This works because others are watching for cues to who is being copied, so substantial mimicry can effectively boost the prestige of the person mimicked. Second, mimicry is a tool that we use to help us get into other people’s minds—to understand their thoughts and preferences. For example, when two people are having a positive conversational experience, getting to know one another, they will be unconsciously mimicking each other, in their body positions, vocal frequencies, movements, and facial expressions—a patterning known as the Chameleon effect. Interestingly, however, since prestige subordinates are keener on understanding what their higher ups are thinking, wanting, and believing, they engage in relatively more mimicry—that is, subordinates unconsciously mimic prestigious individuals more than vice versa.
Part of figuring out who to learn from is attending to whom others are looking at, listening to, and emulating because, in a complex world, doing so can point us in the right direction: toward models we should be learning from. At least, this was the case for most of our species’ evolutionary history. However, in the modern world, this aspect of our psychology may explain how someone can be famous for being famous—the Paris Hilton effect. The nature of our media means that, without trying, many people end up attending to whomever the popular media is covering. An initial media exposure, accidental or by design, creates attention cues that cause people to unconsciously perceive someone as a worthy model. This means that we see others consistently watching certain celebrities and hear others talking about those celebrities because such people provide a shared point of reference for everyone who watches the same media. These attention cues can cause our prestige psychology to automatically infer that these individuals are worthy of our imitation, respect, and admiration. This nonconscious inference also causes increased emulation and mimicry in this group, as they seek physical, or at least social, proximity. This shift can then create a feedback loop, as the media continues to cover those who people want to know more about, and a celebrity is born—seemingly from nothing. A parallel kind of runaway phenomena is described by Duncan Watts for the emergence of renowned paintings like the Mona Lisa and chart-topping popular songs.
In species with cultural learning, while aging individuals may be physically declining, they still possess transmittable know-how that makes them increasingly valuable to younger generations. This accumulated knowledge may explain why the elderly are prestigious in most, if not all, traditional societies. The evolutionary reason is that older age is often a cue that someone is likely to possess knowledge or wisdom, and for this, we humans grant prestige status. It’s also why most other animals don’t respect their elderly.
If the elderly are so often prestigious across human societies, why aren’t they particularly admired or respected in many Western societies? To answer this, we return to the evolutionary logic. The aged are accorded prestige and deference when more decades of experience and learning can provide a proxy measure for accumulated knowledge and wisdom. However, if a society is rapidly changing, then the knowledge accumulated by someone over decades will become outdated rather quickly. Age is only a good proxy if the world faced by the new generation is pretty similar to that faced by the oldest generation. Consider, for example, that the elderly of today grew up in a world without computers, email, Facebook, Google, smartphones, apps, or online libraries. They typed on manual typewriters, mailed handwritten letters, went to bookstores, and could only date people they met in person or through friends and family. In our rapidly changing modern societies, the accumulated knowledge of the elderly is less valuable than it might otherwise be. In fact, the faster things change, the younger and younger the best and most competent models get.
What are the implications of the fact that once we are a cultural species, decades of accumulated individual and cultural learning make us increasingly valuable to younger generations? The longer we live, the more information we accumulate, and the potentially more valuable we are as transmitters of this wisdom, provided the world is relatively stable during one lifetime (which it probably was for most of our species’ evolutionary history). Under these conditions, natural selection should favor extending our lives in order to give us time to transmit our accumulated know-how to our children and grandchildren and to make sure they have the time and opportunity to learn what they will need. As individuals, our cultural stock is going up over the decades while our physical skills are going down, as are our abilities to produce high-quality babies. At a certain point, those lines cross, and it’s time to stop reproduction and focus all of our efforts on the current children and grandchildren. However, given our declining physical abilities, one of the major ways we can help our younger relatives, especially in traditional societies, is by dispensing our accumulated wisdom. This is why humans, but not other primates, live for decades beyond when we stop reproducing, and even live past when we stop being economically productive. This longevity not only emerges in modern societies, but has also now been shown among hunter-gatherers and other small-scale societies, and likely dates back tens or even hundreds of thousands of years into the Paleolithic.
IN-LAWS, INCEST TABOOS, AND RITUALS
The emergence of social norms drove a genetic evolutionary process of self-domestication that dramatically shaped our species’ sociality. This view contrasts sharply with the canonical view of the evolution of human cooperation.
Though humans certainly do possess innate proclivities for helping our kin and engaging in reciprocity, these are, in and of themselves, too weak or narrowly delimited to explain cooperation in real human societies. For example, though motivations to help close relatives can be strong, even in small foraging bands, the average other person is a quite-distant relative, and bands contain many non-relatives.
Cultural learning means that it’s possible for people to acquire notions of how people should behave, both toward others and even in purely nonsocial situations. Deviations from “proper behavior” evoke negative emotions toward the deviant, even in uninvolved third-party observers.
Social norms make it possible for humans to solve—often without anyone understanding how—what would otherwise be inescapable social dilemmas. Social life is riddled with chances to exploit others, which most people don’t even notice. And the more individuals interact and trust each other, the greater the opportunities there are to exploit others—to cheat or free ride on the efforts of others. Culture has several tools and some secret tricks, but two are most important. First and foremost, it brings in third parties to monitor, reward, and sanction others based on local culturally transmitted and widely shared rules. When necessary, it incentivizes third-party actions in some way, often to sanction norm violators. Second, by providing mental models of situations and relationships, it directs our attention away from opportunities to exploit others and reframes situations in ways that tap or harness our instincts in distinct, and often prosocial, ways. Behaviors like smoking, eating horse meat, or littering can go from perfectly acceptable to disgusting, once new culturally transmitted mental connections are made. This is how, over tens of thousands of years, cultural evolution forged primate troops into human communities.
Marriage norms help expand human kinship systems by harnessing our pair-bonding instincts. In doing this, norms variously exploit the shared fitness interests of in-laws, the willingness of men to invest in the offspring of women they’ve had sex with, and the power of namesakes. As societies expanded and became more complex, marriage norms were increasingly used to build intergroup alliances, to promote peace, and to sustain larger-scale forms of social organization.
Human communities—whom we ally with, help, marry, and love—are forged by social norms, which variously harness, extend, and suppress our social instincts. Our species cooperation and sociality is deeply influenced by and highly dependent on culturally evolved social norms, which makes us rather unlike other animals. We acquire social rules by observing and learning from others, and we—at least to some degree—internalize them as goals in themselves. Because cultural learning influences how we judge others, it can create self-reinforcing stable patterns of social behavior—social norms. This view suggests that, stripped of our social norms and beliefs, we aren’t nearly as cooperative or as communal as we might seem. And to the degree that we are more cooperative than other mammalian species (and we are), it’s because culturally evolved norms constructed social environments that, over eons, penalized and gradually weeded out aggressive, antisocial types (norm violators) while rewarding the more sociable and docile among us.
Communal rituals have a potent psychological impact on their participants and create strong personal ties, deep trust, and a profound sense of group solidarity. Recently, however, researchers have begun to systematically measure the effect of communal rituals on social bonding and cooperation and to further break rituals down into their active ingredients. These ingredients include (1) synchronous singing and dancing or other movements (e.g., marching), (2) collaborative music making, (3) extreme physical exhaustion, (4) feelings of a common fate, (5) shared experiences of danger or terror, (6) supernatural or mystical beliefs, and (7) causal opacity or a lack of instrumentality (that is, people are not sure why the ritual must be done in a particular way, but they know it must be done in that way).
Our ability to learn from each other gives rise to sets of social norms, including practices like communal rituals, food taboos, and kinship rules, which strongly influence human social life. In shaping individual decisions, social norms are powerful for a number of reasons, but they generally
Such social norms are crucial for understanding community and cooperation in all human societies, including those of mobile hunter-gatherers.
INTERGROUP COMPETITION SHAPES CULTURAL EVOLUTION
Intergroup competition provides one important process that can help explain the spread of norms that foster prosociality. Different groups culturally evolve different social norms. Having norms that increase cooperation can favor success in competition with other groups that lack these norms. Over time, intergroup competition can aggregate and assemble packages of social norms that more effectively promote such success, and these packages will include social norms related to cooperation, helping, sharing, and maintaining internal harmony.
Over a million years ago, our genus expanded out of Africa into a vast range of Eurasian environments that were experiencing rapid climatic and ecological shifts. To the degree that survival in these evolutionarily new and harsh environments depended on cooperation or social networks to sustain technologies (like fire, bows and arrows, fishing, and clothing), differential extinction would have favored any culturally transmitted behaviors that fostered either.
In more recent millennia, especially since the origins of plant and animal domestication some 12,000 years ago, the intensity of intergroup competition has dramatically escalated, driving the rise of increasingly large and complex societies. At the global level, Jared Diamond has argued that intergroup competition is crucial for explaining the expansion of particular agricultural groups around the globe and that the elevated intensity of this competition in Europe, and Eurasia more broadly, helps explain why it was Europeans who conquered the world after 1500 CE, and not the Aztecs or Warlpiri.
Some of the essential features that distinguish human social life in all societies from that of other species:
When we learn norms we, at least partially, internalize them as goals in themselves. This internalization helps us navigate the social world more effectively and avoid temptations to break the rules to obtain immediate benefits. In some situations, internalizations may provide a quick and efficient heuristic that saves the cost of running the mental calculations that consider all the potential short- and long-term benefits and probabilistic penalties of an action; instead we simply follow the rule and abide by the norm. This means that our automatic and unreflective responses come to match the normatively required ones. Other times, internalized preferences may merely provide an additional motivation that goes into our calculations.
As both Adam Smith and Friedrich Hayek argued long before Erik and me, it’s our automatic norm following—not our self-interest or our cool rational calculation of future consequences—that often makes us do the “right thing” and allows our societies to work. This means that how well a society functions depends on its package of social norms.
Why would natural selection have built us to be norm internalizers? Broadly speaking, internalizing motivations helps us to more effectively and efficiently navigate our social world, a world in which some of the most frequent and dangerous pitfalls involve violating norms. Such motivations may help us avoid short-term temptations, reduce cognitive or attentional loads, or more persuasively communicate our true social commitments to others.
In short, to survive in a world governed by social rules enforced by third parties and reputations, we became norm learners with prosocial biases, norm adherers internalizing key motivations, norm-violation spotters, and reputation managers. This makes us rather unlike any other species.
The world that cultural evolution often creates is one in which different groups possess different social norms and where norm boundaries are often marked by language, dialect, dress, or other markers (e.g., head shape). This social environment would have favored the reliable development of cognitive tools for navigating such a world. In this world, knowing a person’s dialect would have allowed one to predict with some confidence many other aspects of his or her preferences, motivations, and beliefs, because dialects get transmitted along the same learning pathways as social norms, beliefs, and worldviews. The situation may also have favored an evolved psychology for recognizing the groups in the world, determining their markers, and making generalizations about their members using category-based induction. That is, if you learn something about one member of a group—for example, he doesn’t eat pigs—you tend to assume that this applies to all members. Of course, the downside of such tendencies and abilities is that they sometimes yield incorrect inferences and tend to throw the whole social landscape of groups and their behaviors into a starker relief than reality (sometimes) supports. Cognitive scientists call these abilities our folksociological capacities.
This approach to how and why we think about tribes and ethnicity has broader implications. First, intergroup competition will tend to favor the spread of any tricks for expanding what members of a group perceive as their tribe. Both religions and nations have culturally evolved to increasingly harness and exploit this piece of our psychology, as they create quasi-tribes. Second, this approach means that the in-group versus out-group view taken by psychologists misses a key point: not all groups are equally salient or thought about in the same way. Civil wars, for example, strongly trace to ethnically or religiously marked differences, and not to class, income, or political ideology. This is so because our minds are prepared to carve the social world into ethnic groups, but not into classes or ideologies. Finally, the psychological machinery that underpins how we think about “race” actually evolved to parse ethnicity, not race. You might be confused by this distinction since race and ethnicity are so often mixed up. Ethnic-group membership is assigned based on culturally transmitted markers, like language or dialect. By contrast, racial groups are marked and assigned according to perceived morphological traits, like skin color or hair form, which are genetically transmitted. Our folksociological abilities evolved to pick out ethnic groups or tribes. However, cues such as skin color or hair form can pose as ethnic markers in the modern world because members of different ethnic groups sometimes also share markers like skin color or hair form, and racial cues can automatically and unconsciously “trick” our psychology into thinking that different ethnic groups exist. And this by-product can be harnessed and reified by cultural evolution to create linguistically labeled racial categories and racism. Underlining this point is the fact that racial cues do not have cognitive priority over ethnic cues: when children or adults encounter a situation in which accent or language indicate “same ethnicity” but skin color indicates “different race,” the ethnolinguistic markers trump the racial markers.
When disaster threatens and uncertainty reigns, people cling more tightly to their community’s social norms, including their rituals and supernatural beliefs, because it’s these social norms that have long allowed human communities to adhere, cooperate, and survive.
OUR COLLECTIVE BRAINS
Once individuals evolve to learn from one another with sufficient accuracy (fidelity), social groups of individuals develop what might be called collective brains. The power of these collective brains to develop increasingly effective tools and technologies, as well as other forms of nonmaterial culture (e.g., know-how), depends in part on the size of the group of individuals engaged and on their social interconnectedness. It’s our collective brains operating over generations, and not the innate inventive power or creative abilities of individual brains, that explain our species’ fancy technologies and massive ecological success.
Larger and more interconnected populations generate more sophisticated tools, techniques, weapons, and know-how because they have larger collective brains.
If intergroup competition is favoring sophisticated tools and weapons, it has to favor the social norms and institutions that can sustain a larger collective brain—technology and sociality have to coevolve. Since it is far more important for a cultural species to be social than innately smart in producing complex technologies, when we see technological and other cultural flourishing we ought to also consider the realm of the social—the institutions, marriage practices, and rituals—in trying to understand the origins of that cultural flourishing.
COMMUNICATIVE TOOLS WITH RULES
ENCULTURATED BRAINS AND HONORABLE HORMONES
Cultural differences are biological differences but not genetic differences. Human biology, including our brains, involves much more than genes. Oddly, many people, including scientists and science journalists who should know better, often treat cultural differences as if they were nonbiological and nonmaterial, almost otherworldly. This confusion emerges when people think that showing something is “in the brain” or driven by hormones means it’s genetic. This is not the case.
Recent evidence clearly shows how culture can shape biology by altering our brain architecture, molding our bodies, and shifting our hormones. Cultural evolution is a type of biological evolution; it’s just not a type of genetic evolution.
The world is full of cultures of honor, societies with complex sets of social norms that oblige and motivate men and their kin to defend their properties, wives, and families with violence. The social norms here specify that personal or family insults, property damage or theft, and any endangerment to kin jeopardizes a man’s reputation unless he replies with immediate and substantial violence, violence that would seem rather disproportionate to those of us from non-honor societies. Flirting with an honorable man’s wife or girlfriend will get you punched in the face; anything more might get you killed. The cultural evolution of such norms makes good adaptive sense in a world without formal or effective policing institutions, where property such as cows, horses, sheep, and goats can easily be stolen.
Growing up in the social and technological worlds built by cultural evolution changes our biology in profound ways, even when it has not yet had time to alter our gene frequencies. Unconsciously and automatically, we culturally learn motivations, preferences, and values that change our brains in ways that alter what is neurologically rewarding (what we “like”) and endow us with our rapid intuitive responses. This does not mean we can culturally learn to like anything, but it’s worth noting we can learn to enjoy certain types of pain, including muscle soreness and the burn of a chili pepper. We also culturally acquire mental models or beliefs about how the world works, which direct our attention and generate our expectations. These explain why numerous medical treatments (which are purely placebo effects) and witchcraft often actually work and cause important biological effects. Cumulative cultural evolution also produces packages of technologies, practices, and social norms that provide us with the mental and physical tools, as well as the reputational incentives, to change our brains in ways that create whole new cognitive abilities or hone existing capacities.
The key to explaining why our lineage crossed the Rubicon and so many other species have not is to understand how we solved the start-up problem: bigger brains calibrated to rely on learning from others can’t pay for themselves unless there is already a lot to learn out there in the minds of others. So, assuming we are starting with a creature with good individual learning abilities (e.g., big apes), we first consider the conditions that would favor increasing the amount of know-how that one could potentially learn without increasing brain size. Terrestriality gives a boost by providing better opportunities for individual learning and more chances for social learning. Predation, by forcing primates to live in larger groups for protection, increases the size and interconnectedness of groups. Both terrestriality and predation will thereby increase the size of groups’ cultural repertoires and may begin to push a species past the threshold. Nevertheless, expanding brains to store more cultural information still face a crucial obstacle: the high cost to mothers of investing in offspring who take a long time to grow up and learn what they need to know to survive. Even when this pays in the short run for mothers, it can result in extinction in the long run when famines, droughts, and floods hit. Circumventing this constraint, the larger groups of social learners created by predation can also lead to the spread of pair-bonding strategies, which eventually expand kinship circles, increase social learning opportunities, and favor greater alloparental care. Combined with the increased production of high-quality foods made possible by more cultural know-how (due to more social learning opportunities), the alloparental help delivered by relatives and others to mom and her offspring lower her costs in the short and long run, which permits her to produce children more rapidly. This opens the door for a massive expansion of brains, increasingly selected for their cultural learning abilities.
A NEW KIND OF ANIMAL
The case I’ve presented in this book suggests that humans are undergoing what biologists call a major transition. Such transitions occur when less complex forms of life combine in some way to give rise to more complex forms. Examples include the transition from independently replicating molecules to replicating packages called chromosomes or, the transition from different kinds of simple cells to more complex cells in which these once-distinct simple cell types came to perform critical functions and become entirely mutually interdependent, such as the nucleus and mitochondria in our own cells. Our species’ dependence on cumulative culture for survival, on living in cooperative groups, on alloparenting and a division of labor and information, and on our communicative repertoires mean that humans have begun to satisfy all the requirements for a major biological transition. Thus, we are literally the beginnings of a new kind of animal. By contrast, the wrong way to understand humans is to think that we are just a really smart, though somewhat less hairy, chimpanzee. This view is surprisingly common.
Recognizing that we are a cultural species means that, even in the short run (when genes don’t have enough time to change), institutions, technologies, and languages are coevolving with psychological biases, cognitive abilities, emotional responses, and preferences. In the longer run, genes are evolving to adapt to these culturally constructed worlds, and this has been, and is now, the primary driver of human genetic evolution.
Once we understand the importance of collective brains, we begin to see why modern societies vary in their innovativeness. It’s not the smartness of individuals or the formal incentives. It’s the willingness and ability of large numbers of individuals at the knowledge frontier to freely interact, exchange views, disagree, learn from each other, build collaborations, trust strangers, and be wrong. Innovation does not take a genius or a village; it takes a big network of freely interacting minds. Achieving this depends on people’s psychology, which arises from a package of social norms and beliefs, along with the formal institutions they foster or permit.
Can This Help Us Build Stuff?
Once we understand humans as a cultural species, the toolbox for designing new organizations, policies, and institutions begins to look quite different. Here are eight insights drawn from this book.