Few essays have the longevity of “The Two Cultures”, written by the scientist/novelist C.P. Snow in 1959. Working as a physical chemist by day and socializing with his literati friends at night, Snow could testify that his two groups of associates were worlds apart. His scientist friends couldn’t be bothered to read Dickens and his literati friends couldn’t define mass or acceleration. The two cultures coexisted without interacting not only at Cambridge, Snow’s academic home, but around the world.

If Snow’s essay remains current, it is because the problem he identified—broadly, the disconnect between the sciences and humanities—has seemed insuperable. Until now. The breakthrough is easy to understand, at least in retrospect:  The domain of the humanities—variously described as “studies about human culture” (Wikipedia) or “the study of how people process and document the human experience” (Stanford Humanities)—are successfully becoming the object of scientific inquiry. If a scientist who studies physics knows little about culture or a humanist who studies human culture knows little about physics, then that doesn’t interfere much with their work. But if human culture becomes the object of scientific inquiry, then the very distinction between science and the humanities disappears. Scientists must respectfully consult humanist scholars in the same way that Darwin respectfully consulted the naturalists of his day. After all, it is the humanist scholars who have compiled the vast storehouse of information about human cultures around the world and throughout history. It is also the humanists who have done most of the hard thinking about topics such as the nature of symbolic thought. The humanists aren’t necessarily wrong, any more than the naturalists consulted by Darwin were wrong in their observations about plants and animals. What Darwin added was a new way of organizing existing knowledge and the search for new knowledge. That’s also what contemporary evolutionary scientists are trying to add to the study of the humanities. It simply cannot be done without collaboration.

Four new books provide a sample of this collaboration in action. Joseph Henrich’s The Secret of Our Success explains how we became such a cultural species in the first place and how culture has been driving genetic evolution for many thousands of generations. Peter Turchin’s Ultrasociety explains how the scale of human society increased by orders of magnitude over the long sweep of human history, based largely, although not entirely, on warfare. Dominic Johnson’s God is Watching You illustrates how the study of religion—a branch of the humanities by anyone’s definition—is being placed on an evolutionary foundation. Robert A. Paul’s Mixed Messages interprets cultural diversity through the lens of dual inheritance theory, which posits both a genetic and a cultural stream of information that is transmitted across generations.

Before describing their works, the biographies of the authors provide a clue that commerce between science and the humanities has been in progress for a while, even if it is not yet widely known. Each is like an intellectual world traveler capable of navigating to any port of call. Joseph Henrich disembarked from college with a degree in anthropology and briefly became an aerospace engineer before returning to get his PhD in anthropology at UCLA. It was there that he encountered a new brand of anthropology that is centered on evolution and integrates not only the four-field partitioning of that discipline (biological, cultural, archeological and linguistic) but all of the other human-related disciplines as well. He held a 2/3 appointment in psychology and a 1/3 appointment in economics at the University of British Columbia before joining Harvard’s Department of Human Evolutionary Biology, his current port of call.

Peter Turchin’s father was the distinguished Russian physicist and dissident Valentine Turchin. Peter became a mathematical biologist specializing in non-linear population dynamics. At mid-career, he decided to employ the same mathematical and theoretical tools to study human history. He is currently assembling a world history database that he describes as the cultural equivalent of the human genome project, which he can only do with the help of traditional historians.  His primary academic home remains the Department of Ecology and Evolutionary Biology at the University of Connecticut, but he has joint appointments in the Anthropology and Mathematics Departments and prefers to call himself an evolutionary anthropologist.

Dominic Johnson originally aspired to be a natural history filmmaker but switched to an academic track after reading The Selfish Gene. That led to a PhD from Oxford on the evolution of sociality in carnivores. A year at Harvard on a Kennedy scholarship broadened his horizons. He now saw history, politics, economics, religion, and evolutionary biology as all cut from the same cloth. After earning a second PhD in political science and numerous ports of call, he is currently Statutory Professor of Politics and International Relations at Oxford.

Robert A. Paul earned his PhD in cultural anthropology in 1970 at the University of Chicago, where he acquired an exceptionally integrated form of that discipline’s four-field approach. He joined Emory University’s Institute of Liberal Arts in 1976 and helped to build Emory’s anthropology department. His academic specialty is Buddhist symbolic thought. Along the way, he became a licensed psychoanalyst and currently directs Emory’s Psychoanalytic Institute. His current book is influenced by some of the faculty that he hired, including Robert Boyd, who later went to UCLA and became Joseph Henrich’s mentor, and Henrich himself, who made Emory one of his ports of call before moving on to the University of British Columbia.

Perhaps all four of these people are like C.P. Snow—unusually broadminded in contrast to their peers. That would be boring. Far more interesting and likely to be true is a change in the intellectual climate that makes it possible for anyone to become world travelers like these four people. The change is a maturation of evolutionary theory. Put another way, the same theory that unified the study of the rest of life during the 20th century (which continues) is now unifying the study of humanity as part of life.

Already I can imagine some readers of this essay scrambling to grab the rhetorical weapons that were wielded in past battles, such as the controversy over the publication of E.O. Wilson’s Sociobiology in 1975 and the so-called “adaptation war” waged on the pages of the New York Review of Books in the 1990’s. But those weapons won’t do, any more than the cavalry could be used to fight in World War I. Moreover, what’s happening now is not a war but a constructive enterprise that requires turning weapons into plowshares.

One way that evolutionary theory has matured is by expanding beyond genetic evolution. Darwin knew nothing about genes and defined evolution in terms of variation, selection, and heredity–a resemblance between parents and offspring. Once the genes first discovered by Mendel gave rise to the field of genetics during the 20th century, however, they were treated as the only mechanism of heredity. Say “evolution” and most people hear “genes”, as if the only way for offspring to resemble parents (or more generally for information to be transmitted across generations) is by sharing their genes.

That’s patently false, but it has taken a long time for evolutionary theorists to return to their roots and define evolution in terms of heredity, not just genes. This single move expands the view to include other mechanisms of heredity, such as epigenetic mechanisms (trans-generational changes in gene expression rather than gene frequency), forms of social learning found in many species, and forms of symbolic thought that are distinctively human.

On the humanities side, a common formulation is that evolution explains the rest of life, our physical bodies, and a few of our basic urges such as to eat and have sex, but has nothing to say about our rich behavioral and cultural diversity. This is the apartheid that has kept C.P. Snow’s essay current all these years, but it’s important to realize that both sides–the gene-centric life sciences and the gene-phobic humanities—have contributed to the separation.

Before providing an overview of the four books, I would like to anticipate and forestall two objections that are likely to arise in humanist quarters. First, many humanists celebrate diversity and resist the idea that any one thing can be said about all cultures. That is not the meaning of the phrase “The One Culture”, however, any more than Snow was trying to assert that only two things can be said about all cultures. Snow’s point was that the academic world is partitioned into two cultures. “The One Culture” signifies that this partition is breaking down, which is something to be welcomed on both sides. The One Culture is all about the study of cultural diversity, just as evolutionary biology is all about the study of biological diversity.

Second, many humanists are extremely wary of grand narratives that exclude other narratives, which colors their attitude toward evolutionary theory and science as a whole. There are plenty of misuses of evolutionary theory and science in the past to justify such skepticism. One reason that the study of human cultural evolution got off to a bad start is because most European scientists took it for granted that their own culture was superior to all other cultures.  The current generation of scientists doesn’t necessarily have it right either. At the same time, it is widely acknowledged that relativism becomes self-contradictory and useless when it denies the possibility of objective knowledge. The One Culture affords an opportunity for humanists who are acutely aware of cultural differences and the rights of minorities to work constructively with scientists.


The best of our current knowledge about human genetic and cultural evolution is well told for a general audience by Joseph Henrich in The Secret of Our Success. He starts by reminding us of our frailty as a species. We can’t climb trees or outrun predators on the ground. Our stomachs, colons, and teeth are wimpy compared to other mammals with roughly the same diet. Our babies are born ridiculously premature. And, despite our large brains, we’re not that smart as individuals. Culture is the secret of our success and it has been playing a key role for so many generations that it has redirected genetic evolution, resulting in our odd suite of physical and mental characteristics.

Henrich uses anecdotes in addition to scientific studies to hammer home the point that we owe our success to culture and not our individual intelligence. A whole chapter is devoted to European explorers who got stranded and were unable to survive on the land without the help of native people. Generations of accumulated experience were required, not smart people figuring out what to do on the spot. Hardy European explorers were helpless, but a single native American woman who became stranded on her home island in California’s Channel Islands when the rest of the population was evacuated survived for eighteen years on her own. As Henrich tells the story:

[T]his lonely castaway ate seals, shellfish, sea birds, fish, and various roots. She deposited dried meats on different parts of the island for times of sickness or other emergencies. She fashioned bone knives, needles, bone awls, shell fishhooks, and sinew fishing lines. She lived in whalebone houses and weathered storms in a cave. For transporting water, she wove a version of the amazing watertight baskets that were common among the California Indians. For clothing, she fashioned waterproof tunics by sewing together seagull skins with the feathers still on and wore sandals woven from grasses. When finally found, she was described as being “in fine physical condition”…After overcoming an initial scare at being suddenly found, the lone woman promptly offered the search party dinner, which she was cooking at the time they arrived.

Even indigenous populations can lose their ability to survive if cultural information becomes lost.  Sometime during the 1820’s, an epidemic killed many of the oldest and most knowledgeable members of an Inuit population that lived in an isolated region of northwestern Greenland. The loss was like a collective stroke for the culture. The survivors were unable make effective bows and arrows, heat-trapping entrances to their snow houses, or build kayaks. Even they were unable to recreate this knowledge and their population had dwindled by the time they were contacted in the 1860’s by another Inuit population from around Baffin Island. Only then did the northwestern Greenland population begin to expand, thanks to the replenished cultural toolkit obtained from the Baffin Island population. Another “collective stroke” took place in Australia when what is now the island of Tasmania was cut off from the mainland by rising sea levels. The population stranded on the island was not large enough to collectively remember and transmit the knowledge of the culture and they lapsed into a more rudimentary existence.

Readers who are not already familiar with stories such these will be impressed by the amount of knowledge that is required for native people to survive and reproduce in challenging environments, which is not in their genes. Nevertheless, a genetic evolutionary story is required to explain why we are the only species on earth that can transmit learned information across generations to this degree. And a psychological (and ultimately neurobiological) story is required to understand the proximate mechanisms that make cultural retention and transmission possible. These are the pieces of the grand puzzle of humanity that are beginning to fit together. Seeing the whole puzzle is what it means for “The Two Cultures” to become “The One Culture”.

Turning to the psychological piece of the puzzle, consider the following experiment: Preschool children watch a video of two people (called models) manipulating the same object in two different ways. In the video, two bystanders enter, look at both of the models, and then preferentially watch one of them. The video goes on to show the two models selecting different foods, drinking beverages of a different color, and playing with a single toy in two different ways. After watching the video, the preschool children are given the opportunity to choose between the different foods and beverages and to play with the toy any way they want. The results: children were four times more likely to eat the food and drink the beverage and thirteen times more likely to play with the toy in the same way as the model that the bystanders were watching.

Or consider an experiment that involved adult men and women copying the hand motions of a same-sex or other-sex model while their brains are being scanned. Copying the same-sex model resulted in higher activation of the nucleus accumbens, dorsal and ventral striatum, orbital frontal cortex, and left amygdala—the same circuitry that is activated by receiving a reward such as money for getting a correct answer. Copying from some people rather than others is neurobiologically more rewarding.

These and many other experiments recounted by Henrich demonstrate that while some genes might code directly for human behaviors, many other genes code for a complex system for acquiring behaviors from one’s culture, which operates largely beneath conscious awareness and begins before birth. Critics of biological determinism have been proclaiming “Not in our genes!” all along, but a scientific account of the human cultural acquisition system that does emanate from our genes can only make their argument stronger. Indeed, without a scientific account, it is difficult to see how the humanities can achieve its own stated goal of understanding how people process human experience.


The new evolutionary story goes not only beyond genes, but also beyond selfishness. A theory called multilevel selection, which began with Darwin but was rejected for much of the 20th century, has become indispensible for understanding human genetic and cultural evolution. As Peter Turchin puts it in Ultrasociety:

Such a multilevel nature of organization of economic and social life has profound consequences for the evolution of human societies–just how profound we are only now beginning to understand, thanks to Cultural Evolution. The central theoretical breakthrough in this new field is the theory of Cultural Multilevel Selection.

Cancer provides a quick way to describe multilevel selection. Malignant cancer cells proliferate faster than their neighboring normal cells, making them perversely adaptive from an evolutionary perspective. Organisms that manage to suppress cancer proliferate faster than organisms susceptible to cancer. Natural selection therefore operates at two levels: a lower level that favors cancerous traits and a higher-level that favors “for the good of the organism” traits. Eons of higher-level selection has resulted in multi-cellular organisms that are remarkably (although by no means perfectly) resistant to cancer.

Now frame-shift upward so that the lower level is comprised of individuals competing within social groups and the higher level is comprised of social groups competing in a multi-group population. While you’re at it, contemplate a multi-tier hierarchy of groups within groups within groups. At every rung of the hierarchy, lower-level selection tends to favor traits that are cancerous at higher levels.

Most animal social groups reflect a combination of within- and between-group selection—some cooperation mixed with a lot of disruptive competition. To the best of our current knowledge, our ancestors managed to suppress disruptive self-serving behaviors within their groups to a remarkable degree, so that between-group selection became the dominant evolutionary force. This is called a major evolutionary transition and it has happened before in the history of life, including the evolution of social insect colonies, multi-cellular organisms, nucleated cells, and perhaps even the origin of life itself as groups of cooperating molecular reactions.

Nearly everything distinctive about our species can be understood as a form of teamwork made possible by a major evolutionary transition, including our ability to encode information in symbolic meaning systems and transmit large amounts of information across generations—in other words, our very capacity for culture. However, multilevel selection doesn’t make everything nice. It is part of the theory that teamwork within groups is forged by competition among groups. Among group competition need not take the form of warfare—but it often does.

Turchin disagrees with Steven Pinker’s thesis in The Better Angels of Our Nature that the incidence of warfare has been declining since the earliest times. Turchin regards an inverted U-shaped curve as more likely: Not much warfare when population density was low and human groups could be widely dispersed, then more as population density increased, and then less over the course of recorded human history. At a finer grain, human cultural evolution can be seen as an eternal conflict between levels of selection with a net gain for higher levels of functional organization, leading to the remarkably well-organized mega-societies of today–although with many reversals and much carnage along the way. Historians, archeologists, and paleontologists are required to interpret the fossil record of human cultural evolution in terms of this overarching theoretical framework.

Following Turchin, let’s drop in on two periods of human history, as revealed by written inscriptions on clay and stone tablets. The first is from Tiglath Pileser I, who ruled the Assyrian Empire from 1114-1076 BCE:

Then I went into the country of Comukha, which was disobedient and withheld the tribute and offerings due to Ashur my Lord: I conquered the whole country of Comukha. I plundered their movables, their wealth, and their valuables. Their cities I burnt with fire, I destroyed and ruined…Their fighting men, in the middle of the forests, like wild beasts, I smote. Their carcasses filled the Tigris, and the tops of the mountains…The heavy yoke of my empire I imposed on them.

And here is one from Ashoka the Great, who ruled the Mauryan Empire in the region of current day India and Pakistan during 268-239 BCE:

Beloved-of-the-Gods speaks thus: This Dhamma edict was written twenty-six years after my coronation. My magistrates are working among the people, among many hundreds of thousands of people. The hearing of petitions and the administration of justice has been left to them so that they can do their duties confidently and fearlessly and so that they can work for the welfare, happiness and benefit of the people in the country. But they should remember what causes happiness and sorrow, and being themselves devoted to Dhamma, they should encourage the people in the country to do the same, that they may attain happiness in this world and the next.

Even adjusting for boastfulness in both Emperors, what they chose to boast about speaks volumes about a brutal despotic culture on one hand and a more gentle inclusive culture on the other. What accounted for the flowering of social justice (relatively speaking), not just in the Mauryan empire but throughout Eurasia? According to Turchin, not the cessation of warfare but an increase in the scale of warfare.  The bullying tactics of despots who declare themselves to be Gods don’t work above a certain scale. An equitable society that holds even its kings accountable is required to create a mega-empire that spans millions of square kilometers and includes tens of millions of people.  The religions and philosophies that evolved during the so-called Axial Age (roughly the 8th to 3rd centuries BCE) provided the social glue capable of holding such large societies together.


For reasons that are largely serendipitous, The One Culture has coalesced around the topic of religion sooner than other topics such as history. Religions puzzle the secular imagination because their beliefs depart so flagrantly from factual reality and result in practices that seem so wasteful. It’s easy to understand why people make blankets, but why do they burn them in sacrifice to Gods for whom there is no verifiable evidence? This question has two potential answers: First, religious beliefs and practices might be just as irrational and wasteful as they seem and persist as byproducts of psychological and social processes that are useful in non-religious contexts. Second, despite appearances, religious beliefs and practices might have their own logic and utility after all.

Emile Durkheim was an early proponent of the latter view. He famously defined religion as “A unified system of beliefs and practices relative to sacred things…which unite into one single moral community called a Church, all those who adhere to them.” Durkheim also stressed the importance of symbolic thought in the organization of human societies: “In all its aspects and at every moment of history, social life is only possible thanks to a vast symbolism”.  Nevertheless, over a century of scholarship in the humanities and social sciences has not led to a consensus on the “secular utility” of religion, as Durkheim put it. The tradition of functionalism that he initiated peaked in the mid-20th century and is currently disparaged in many quarters. When I was writing my own book Darwin’s Cathedral at the turn of the 21st Century, the most authoritative theory of religion was a byproduct theory inspired by economics, which held that Gods are imaginary beings that people invent to bargain with for goods that can’t be had, such as rain during a drought or everlasting life.

Evolutionary biologists are accustomed to studying whether a given trait qualifies as an adaptation vs. a byproduct, the unit of selection, and so on. When this theoretical toolkit started to be applied to religion, it established a consensus that did not previously exist: Appearances notwithstanding, most enduring religions have an impressive degree of secular utility at the level of the religious community, much as Durkheim posited. Religions are also replete with byproducts, just as biological adaptations are, but the view of religion writ large as a byproduct has been authoritatively rejected.

Dominic Johnson’s God is Watching You is built upon this foundation and can therefore ask a more refined question: How do religions cause people to cooperate? The answer to this question comes in three parts. First, cooperation in any species can evolve only if certain conditions are met. This is not just a human universal; it is also an evolutionary universal. In particular, when members of a group are not genetically closely related (and often even when they are), the ability to detect and punish disruptive self-serving behaviors is required for cooperative behaviors to evolve. “Policing” has become a key term in the study of multi-cellular organisms and social insect colonies, no less than the study of human societies.

Second, a suite of policing mechanisms evolved by genetic evolution in our species and operates in nearly all cultures (there is also ongoing genetic variation and selection for these mechanisms). These include a strong bias toward thinking that good behavior will be rewarded and bad behavior will be punished over the long term. Few of us can shake this feeling and nearly all cultures exhibit the bias in both religious and non-religious manifestations. In the plays of Henrik Ibsen, for example, the characters are often tormented by the 19th Century European belief that one’s own moral failings will be passed, like a disease, to one’s offspring. This was not a religious belief, but it had the same effect on policing good behavior as a belief in heaven and hell.

Third, a common set of genetically evolved psychological mechanisms is like a bucket of Lego blocks that can be used to build a nearly infinite variety of cultural forms. This is why the One Culture is capable of explaining human cultural diversity in addition to human cultural universals, from the cosmologies of hunter-gatherer societies, to the moral high Gods of the Abrahamic religions, to Buddhist doctrines of reincarnation. As an intellectual world traveler, Johnson, like Turchin and Henrich, establishes trade routes between the biological sciences, human-related sciences, and humanities to explore a theme that most people would associate with the humanities alone—fear of God.


I have included Mixed Messages in this review to emphasize how much someone trained in the humanities, such as Robert A. Paul, has to offer the One Culture. Most of the knowledge that we possess about human cultural diversity, including the interpretation of human cultures as symbolic meaning systems, resides in academic disciplines associated with the humanities. The knowledge is largely descriptive, lacking the trappings of modern science, but so was the knowledge of the natural historians that Darwin relied upon to piece together his theory of natural selection. Quantification refines, but does not define the scientific process. In this spirit, Paul interprets some of the vast storehouse of information accumulated by socio-cultural anthropologists, which is often dumbfounding from the perspective of genetic evolution alone but makes sense from a broader evolutionary perspective.

Consider adoption, the practice of raising children that are not your own. A narrow genetic view holds that people around the world should favor raising their own offspring or those of their genetic relatives. Adopting offspring from other cultures seems inexplicable. From a broader evolutionary perspective, the basic demographic equation for a culture includes two inputs, birth and immigration, and two outputs, death and emigration. A culture that becomes organized to supplement its own offspring with offspring absorbed from other cultures will grow faster and potentially gain a competitive advantage over neighboring cultures, especially under conditions of chronic warfare. As expected from this broader perspective, the adoption of children captured in warfare was a common practice in cultures around the world and was even the primary demographic input in some cultures, such the Marind-Anim of New Guinea. The Shakers and other celibate religious sects provide examples from social contexts other than warfare. Indeed, childlessness in all its forms ceases to be such a mystery.

Dual inheritance theory can even explain the widespread view that one’s culture is “higher” than biological reproduction, which is by no means restricted to our own culture. Paul puts it this way at the start of a chapter titled “The Asymmetry of Cultural versus Genetic Reproduction”.

[M]atters relating to motherhood and birth are frequently conceptualized as dangerous, polluting, repulsive, shameful, or in other ways problematic, and even as threats to the integrity of society and of human life and health. At this point in my own argument, I hope this situation is not surprising. It is a consequence of the different agendas pursued by the genetic and the cultural programs. The birth of every individual as a helpless organism from a woman’s womb is perhaps the most fundamental scandal challenging the integrity of the claims of the cultural system to independence from biology, and as such it is very widely (although not universally) culturally devalued in one way or another. In this chapter I focus on some ways in which human social systems denigrate, devalue, restrict, or otherwise oppose the biological process by which new human phenotypes are created to populate and thus reproduce those same social systems.

How ironic, that the same asymmetry might explain the widespread view in the humanities that culture cannot be “reduced” to “mere” biology. As someone from the humanities who has joined the One Culture, Paul has created a trade route that hopefully will become well traveled by his colleagues.

I am not bothered by the longevity of C.P. Snow’s essay because when it comes to cultural evolution, the future is not predicted by the past. Anyone with an adventurous bone in their body should be excited by the prospect of becoming an intellectual world traveler, like these four authors. They are not special people, or at least no more special than the many thousands of gifted authors who preceded them. They are merely employing a way of thinking that enables them to visit any port of call in the biological sciences, human-related sciences, and the humanities. Read these four books (I recommend the order that I have reviewed them), and you might well be on your own way.