REVIEW: The Secret of Our Success, by Joseph Henrich

The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter, Joseph Henrich (Princeton University Press, 2015).

There are books that have had a greater influence on my thinking, and there are certainly books I’ve devoured with greater enjoyment, but The Secret of Our Success is probably the book I think about the most relative to how much I actually liked it. Henrich’s exploration of cultural evolution is good pop science: mostly not original material (and where it is, it’s psych lab studies that probably don’t replicate), but nevertheless well-presented and an engaging, accessible explanation of the developing field. It suggests some important questions, implies some surprisingly reactionary conclusions, and provides a grounding for other things I’d like to discuss in the future.¹ So let’s jump right in.

We should start by clarifying exactly what we mean when we say “culture,” and Henrich’s definition is a pretty good one: culture is “the large body of practices, techniques, heuristics, tools, motivations, values, and beliefs that we all acquire while growing up, mostly by learning from other people.” This obviously involves physical technologies like ceramic techniques — archeologists often refer to an unknown people as “the [A Particular Way They Make Their Pots] culture” — but it also includes what we might call social technologies, everything from norms about queuing behavior to the institution of “in-laws” to the Iroquois practice of forcibly adopting enemy combatants into the group to replace fallen relatives or the medieval Icelandic transferrable right to prosecute a crime. Cultures generally come as bundles of related technologies: the Inuit kayak/leister/archery package won’t do you much good without the warm-clothes and snow-house technologies that allow you to stay warm in the Arctic, and arguably Inuit social technologies about emotional expression (don’t) and fictive kin-making (if you let a guest sleep with your wife he becomes your brother) go along with these because they encourage social stability in extremely close quarters.² And it’s the existence of these social technologies, rather than toolmaking either physical or cognitive, that I find the most interesting — and the least discussed by Henrich himself. But before we can get there, I want to run through the big picture of the book for necessary context.

Henrich tackles the question of “culture and evolution” in two ways. He starts out with the less contentious, arguing that for at least the last million years our biological evolution has been driven more by our culture than by changes to our physical environment. Most primates, for instance, have huge guts, enormous molars, and powerful jaw muscles that allow them to chew and digest rough, fibrous plant matter. You, however, don’t. Feel up the side of your head as you open and close your jaw; you’ll find that the muscles you use for chewing stop around the level of your ear. Some of our australopithecine relatives’ jaw muscles went all the way up the sides of their heads and beyond, anchoring to a special bony crest at the top of the skull. We don’t need that, though, because we outsourced all that metabolically demanding muscle and gut (never mind the time it takes to gather and chew all that vegetable matter — gorillas spend half their day eating) to the mechanical processing and pre-digestion by heat or acid that we call “cooking.”³

Cooking: the reason your skull doesn’t look like this.

There are plenty of adaptations more recently, of course. Consider lactase persistence, independently evolved among at least three different populations of pastoralists for whom the ability to drink animal milk into adulthood would have opened up a valuable new source of calories — but not among other pastoralists who had developed fermentation techniques that removed most of the lactose from their dairy products. Or the AMY1 gene, which codes for a protein that helps the saliva to break down starchy foods: the Hadza, an African hunter-gatherer group who have been genetically and geographically isolated for tens of thousands of years in an environment rich in starchy tubers, have up to fifteen copies of the gene, where groups whose historical diet is not high in starch tend to have many fewer copies. And similarly for the gene-culture coevolution that leads to pale skin among agriculturalists but not foragers at high latitudes (cereal crops being much lower in vitamin D than fish or meat), and so forth.

So far, so familiar from any book about human evolution, but most of Henrich’s time is spent showing that it goes the other way, too: our material circumstances drive changes in our culture. The tremendous variety of fishhooks across Oceania are just as adapted to each island’s unique conditions as the beaks of Darwin’s finches, but unlike the finches a fishhook “generation” can be as rapid as a few fishing trips — and more importantly, the alterations don’t have to wait for a beneficial de novo mutation. All it takes is one person fiddling with the design and someone else watching. Humans have substantial raw brainpower compared to other primates, but the real secret sauce is our ability to learn from watching others and our sophisticated mechanisms for choosing whom to watch. Even as babies, we naturally monitor the competence and relative prestige of those around us and preferentially adopt the behavior of the most successful.⁴ Occasionally (through chance or inspiration), we innovate on it. Thus does culture evolve.

It seems like an obvious point, but the consequences of cumulative evolutionary change can be as dramatic in culture as in genetics. Genetic evolution gave you eyes; cultural evolution has given you the ability to read this, as well as a base-10 counting system, Arabic numerals, a vocabulary an order of magnitude larger than that of most small-scale societies, eleven color terms where some people only have “light” and “dark,” clocks, fractions, right vs. left, and tools that many cultures have lacked like the wheel, the pulleys, screws, projectiles, elastically stored energy (as in bows or stringed instruments), levers, poisons, compressed air, and rafts. It’s also given you marriage, religion, the state, and countless other social technologies that govern the ways we behave towards each other and our expectations and preferences about social interaction.

Successful social technologies (those that enable their holders to thrive; this isn't a moral judgment) generally enlarge the group with whom we can live peacefully. Take kinship norms, for instance, always a favorite of anthropologists: like all primates, humans are hardwired to show a strong preference for biological relatives. Compared to strangers, we’re much more likely to help kin, and much less likely to cheat, rob, or murder them even if we can get away with it. But even the smallest-scale societies are made up of plenty of people who are not biologically related to one another, and who nevertheless manage to (mostly) live in harmony. (This isn’t to say they live in utopian bliss, but given that the modal small-scale society response to encountering an outsider is murder if you can get away with it, it’s not bad.) The key is social norms that redirect our innate kin-orientation toward non-kin: marriage, first of all, but also in-laws (“my wife’s brother is my brother”) and extended family (“my parallel cousin⁵ is my brother”). These kinship norms allow their possessors to live peacefully in much larger groups: in the average hunter-gatherer band, about a quarter of the other members are your biological relatives, but three-quarters are your social kin. (The remaining quarter are probably biologically or socially related to some of your family members.) And this can be a big advantage! A larger group is better able to defend itself against outsiders, is more likely to contain particularly skilled hunters or craftsmen from whom the young people can learn, is less likely to lose technology (more on this below), and is less likely to be completely wiped out by a disaster.

Adaptive technologies spread just like adaptive genes do — by enabling their holders to outcompete or displace their neighbors — but unlike genes, they can also be intentionally adopted. In 1971, an anthropologist in the New Guinea village of Irakia observed as the elders of the village convened a series of meetings to address a serious problem: they didn’t have enough pigs. This might sound silly, but for a subsistence agricultural society in the highlands of New Guinea, where pigs are the most important domesticated animal, it meant poverty and low prestige, and the solution they settled on was to copy wholesale the pig-raising practices of their more successful neighbors, the Foré. This included what seems to us fairly common-sense elements, like planting more sweet potatoes to feed the pigs and not killing pigs for breaking into someone’s garden, the adoption of Foré dispute-resolution practices for all disputes involving pigs, and also the seemingly bizarre measure of communal rituals in which they sang, danced, and played flutes for the pigs. Singing to pigs seems like obvious nonsense to us, because we have a culturally evolved set of heuristics about cause and effect in the physical world, but for the people of Irakia, who don’t, it makes perfect sense to adopt the entire package. It’s much easier to see that something is working for the Foré than it is to sort out exactly what is working. In fact, in tracking down the citation for this story, I discovered that in the subsequent thirty-or-so years, the Irakians decided that even Foré-style pig husbandry had failed to bring them the prestige and prosperity they wanted and so instead they yet another bundle of technologies from a different, even more successful neighbor: they stopped raising pigs altogether, switched from subsistence farming to raising commodity crops for cash, and became Christians. It’s worth noting here that the people of Irakia already had some fairly sophisticated social technologies: they had a council of elders who could make decisions for the village as a whole, which the people by and large obeyed (although whether that’s adaptive in this case I’ll leave as an exercise to the reader). But it’s the wholesale adoption of alternative cultural packages that really grabs my attention, because despite the probably pointless pig serenades this is actually a remarkably good heuristic.

Let’s consider the manioc.⁶ Manioc, also known as cassava, is a starchy tuber that tolerates drought, thrives in marginal soil, produces more calories per acre of land cultivated than rice, wheat, or maize, and stays quite fresh in the ground for a long time until you come back to harvest it. You may have eaten it in the form of fried yucca at a South American restaurant, or enjoyed its extracted starch (tapioca) in pudding, the pearls in bubble tea, or my favorite gelling agent for fruit pies. So why don’t we all eat more of it? Well, James C. Scott would say that states suppress manioc and other tuber-rich cuisines because you can’t tax a crop that grows in clearings hidden deep in the jungle and can be harvested at will. (Grains, by contrast, need large, open fields so state officials can surveil both the crops and their cultivators, and they all come ripe at once so it’s easy to swoop in and take the taxes.) But the other reason is that the wonderfully large, hardy, drought-tolerant manioc is full of cyanide.

Still life with cyanogenic tuber.

Manioc actually comes in two varieties. The small “sweet” manioc contains some cyanogenic compounds, but boiling is enough to destroy them. The larger “bitter” manioc, however, which is the one that grows so easily and is so beloved of anarchists, requires complex multi-step processing to make it safe for human consumption. In the Amazon, where manioc was originally domesticated and where it still forms the bulk of traditional diets, women spend a staggering 25% of their day processing manioc: they scrape and grate the roots, then wash the resulting material to separate the fiber, starch, and liquid. The liquid can be boiled and drunk immediately, but the fiber and starch must sit for at least two more days before they can be safely used. Raw or poorly-cooked bitter manioc is enough to kill you (as it did many during recent Venezuelan shortages), but simple boiling, as with sweet manioc, is enough to remove the bitter taste and the risk of acute cyanide poisoning. For the harried Amazonian mother, this time-saving trick might seem like a god-send…until the chronic cyanide poisoning catches up with her family and they end up with exciting symptoms like goiter, ataxia in the legs, and chronic pancreatitis.

Manioc processing is just one example of what Henrich calls “causally opaque” technologies. They’re clearly well-adapted to their circumstances — people in the Amazon don’t have elevated levels of cyanide in their systems — but none of the people deploying these technologies know how or why they work, nor do they care. Of course, in theory you could carefully test each element of an apparently successful suite of technologies to see which ones are actually necessary and which are mere window-dressing pig-serenading, but since you’re also trying to feed your family and the effects of chronic cyanide poisoning take years or decades to appear this is completely impractical — especially without complicated lab equipment and concepts about experimental technique. (As it turns out, modern industrial manioc concerns, which do have access to those things, have converged on processing techniques very similar to those employed by the Amazonians. See? Cultural evolution is just as “smart” as genetic evolution!)

Henrich argues that, because so many highly adaptive technologies are causally opaque, inborn human psychology has evolved the heuristic “do what the people around you are doing rather than trying to figure it all out for yourself.” And this is an important reminder, especially for people reading this review — you’re probably from a culture that emphasizes rational thinking, causal models, and cost-benefit analysis, but those mental tools are all layered atop millions of years of hominin evolution that favored those who copied their most prestigious neighbors, pig-songs and all. Even if you think you’re rationally selecting your behavior on the basis of your principles, values, and models of the world, you’re probably mostly copying whoever’s around you. But all isn’t lost! Simply move that rational, principled choice up one level and choose to be around the people you want to be like. You’ll find yourself growing more like them without even trying.

Of course, there’s a danger to this heuristic: the technologies around you might not be good ones. In fact, many societies have relatively poorly adapted technologies, and though the consequences aren’t usually as serious as cyanide poisoning, even five hundred years since the Portuguese introduce manioc (but not manioc processing techniques) to West Africa there are still a number of African populations who suffer from chronic cyanide poisoning. As long as your culture isn’t so full of maladaptation that you die before you can pass it to your children, then, it can limp along perpetuating itself until either your descendants adopt the culture of their more successful neighbors or those neighbors wipe them out. When cultural adaptationist/“evolutionary” arguments came into vogue in the 1970s, the late UCLA anthropologist Robert Edgerton dedicated an entire book to this phenomenon, aptly titled Sick Societies: Challenging the Myth of Primitive Harmony. It’s a depressing read but a useful corrective to Henrich’s generally sunny account of the brilliance of cultural evolution: sometimes the blind process of cumulative cultural evolution gives you complicated manioc processing techniques, and sometimes it gives you a wedding night where the new bride is expected to have sex with every male member of her husband’s extended family, which frequently causes infertility due to pelvic inflammatory disease and fallopian scarring. On a long enough time-scale these maladaptive technologies will die out, either because they’re abandoned or because their practitioners die out, but that’s cold comfort to anyone who possesses them today. And yet because of the causal opacity of culture it’s hard to tell whether any given practice (especially the complicated or unpleasant kind we’d like to drop) is actually accomplishing anything. Evaluating artifacts is usually pretty simple — does this knife cut or not? does it cut better or worse than that knife? — but anything more complex can be difficult to judge. Here are some clues you might look for, for any kind of culturally evolved technology, when you’re trying to decide whether to do something:

• How long have people been doing it this way? Poorly adapted technologies tend to die out eventually, which makes technology lindy: the longer any given technology has been around, the longer it’s likely to be around. If people have been eating ungulates that ate grass for millions of years and ungulates that ate other ungulates for fifty years, you should go for the grass-fed beef.

• How many other options do people have for how to do it? A small-scale society that has little contact with other cultures may have hit a local maximum without having actually found a particularly good solution, while a technology that has persisted despite its practitioners’ having had the opportunity to defect or adopt other models is more likely to work well.

• How many people do it this way? Well-adapted tools, institutions, norms, and other technologies spread, either because the original population outcompeted their neighbors or because the neighbors adopted them too. Poorly-adapted technologies or institutions can persist for a surprisingly long time but rarely expand their range. It’s the same reason small organizations are more likely to be dysfunctional: the ones that work well grow!

There’s another major danger to small-scale societies, too: they’re prone to losing technology. Any nonliterate group (which is most humans for most of our history) will depend entirely on oral tradition to transmit its information, and will thus be intensely vulnerable to any shock that removes a part of what Henrich calls its “collective brain.” In the 1820s, the Inuit of northwestern Greenland were hit by an epidemic that killed all the oldest and most knowledgeable members of the community. The effects were catastrophic: even though the surviving Polar Inuit had spent their entire lives observing the full Inuit technology suite, they were no longer able to make fishing spears (no fishing for the plentiful arctic char), bows and arrows (no hunting caribou), or kayaks. The loss of kayaks was the most damaging: their only way of reaching other communities had been by sea, and without kayaks they were cut off from any other models for all the other technology they’d lost. When in 1862 some Inuit from Baffin Island happened to stop along their coastline, the Polar Inuit immediately copied their ways of doing things, including Baffin Island-style kayaks, although they eventually adopted a kayak style from other western Greenland Inuit which was better suited to the local conditions.

The case of Tasmania is even more dramatic. Here’s Henrich:

When the earliest European explorers made contact with the Tasmanians in the late eighteenth century, they discovered a population of hunter-gatherers equipped with the simplest toolkit of any society ever encountered (by Europeans). To hunt and fight, men used only a one-piece spear, rocks, and throwing clubs. For watercraft, the Tasmanians relied on leaky reed rafts and lacked paddles. To ford rivers, women would swim the raft across, towing their husbands and offspring. In the cool maritime climate, Tasmanians slung wallaby skins over their shoulders and applied grease to their exposed skin. Curiously, the Tasmanians did not catch or eat any fish, despite fish being plentiful around the island. They drank from skulls and may even have lost the ability to make fire. In all, the Tasmanian toolkit consisted of only about twenty-four items.

Tasmania is separated from the Australian mainland by about 150 miles of ocean, and on the other side of the Bass Strait in Victoria are a group of Pama-Nyungan-speaking Aborigines with a vastly more complex toolkit, including hundreds of multi-part tools, canoes with paddles, sewn and tailored clothing, fishing hooks, and much more. But until sea levels rose around 12,000 years ago, Tasmania was part of the Australian mainland, and until the Tasmanians became geographically isolated their archeological remains are indistinguishable from their contemporaries in Victoria. Even after the rising seas cut them off, they continued to fish and use bone tools for thousands of years until the evidence gradually disappears from the archeological record. We can only imagine the series of catastrophes that befell the Tasmanians’ “collective brains” and caused them to lose even the ability to make fire.⁷

The implications of this are frankly terrifying. Technologies, once lost, are difficult or impossible to recover, and as damaging as it can be to lose the knowledge for making important tools like boats or boomerangs, losing social technologies can be worse. Of course it’s impossible to say whether this happened to the Tasmanians because social behavior from thousands of years ago isn’t preserved like ancient bone tools (though it is worth pointing out that at the point of European contact the Tasmanians did have an unusually dysfunctional relationship between the sexes even by the standards of small-scale societies),⁸ but we can find examples of lost social technology much closer to home.

If you read the sort of books I do, you’re already familiar with the story of the Israeli daycares. Here’s the short version: daycare centers in Haifa were frustrated because parents were often late to pick up their children. Children were supposed to be picked up by 4pm, and parents were rarely more than half a hour late, but it was still inconvenient for the staff who had to rotate the duty of staying past closing time to supervise the remaining children. They were thus receptive when some behavioral economists showed up and asked them to participate in a study on the effect of fines. Half the participating daycares were instructed to institute a fairly mild fine: ten Israeli shekels for a delay of ten minutes or more. (For scale, an hour of babysitting at the time cost 15-20 shekels.) Of course, you know what happened next: parents started showing up late much more often. This counterintuitive outcome is usually trotted out to emphasize the differences in how people regard market and non-market activities: an explicit price for what had been previously interpreted as the staff’s non-market generosity in staying late meant parents now regarded lateness as a good they could purchase, and did so at their convenience. The authors’ opinion is clear in the title they chose for their paper: “A Fine is a Price.” But what I hadn’t realized until recently, because my exposure to this story had been entirely from libertarians, is that after three months the fines were removed…and the parents kept showing up late. Now, I have no reason to disagree with the general interpretation of these results — we obviously do think and feel differently about market activities (you would gratefully eat a meal at your mother’s house that you would send back at a restaurant, even if getting to your mother’s house cost you the price of a dinner out) — but that’s just the causal mechanism. The result is that the parents lost their “punctual pickup” social technology. Whatever combination of shame, empathy for the teachers, duty to their offspring, etc. had led to their avoiding lateness was gone (or at least going), and removing the fine didn’t bring it back.⁹

This should scare you. Our cumulatively culturally evolved social technologies, just like our genomes, are an incredibly complicated, opaque system full of unseen feedback loops and seemingly useless elements that turn out to be load-bearing. They’ve enabled us to build a society of historically unprecedented scale and complexity, and with an unusually high level of social trust (especially for the scale). And because everyone so deeply internalizes the norms of their society, we tend to assume that the way we do things — monogamous lifelong pair-bonding, obedience to rules even in the absence of any possibility of sanction for their violation — is simply “human nature.” But it’s not. Like our genes, our cultures are the product of a millennia-long process of imitation, adaptation, and innovation that’s “smarter” than we are. Unlike genes, culture can be lost through sheer ignorance and lack of practice…or intentionally set aside.

As I've been writing this review, I’ve also been making my way through the works of Jane Austen for the first time.¹⁰ And, probably because I’ve been doing it while writing this review, I keep being struck by the profound differences between the social norms of the world I know and the world of the landed gentry of the Regency period. Some of the social technologies we've “lost” are no longer adaptive, like the “introduction,” without which it is entirely improper to address a stranger.¹¹ Sure, “introducing people” hangs around in vestigial form like the human appendix, but mostly as a convenience or as a salve to the awkward or the shy; we now consider it completely appropriate to introduce ourselves, probably with a broad smile and hand outstretched, in a way no lady or gentleman would ever have countenanced. Then again, in a world of background checks and credit reports (and where your acquaintances are unlikely to stay in your house for weeks or months) it's probably less pressing to have this social version of a professional referral. But we've also lost much of our hierarchy and its accompanying noblesse oblige (meritocrats are supposed to have earned their position and don’t oblige nobody nothing), and we’re currently busily at work kicking down the elements that support one of what Henrich calls our key social technologies: we’re losing the ability to get and stay married.

Don’t believe me? Look at the hours of futile swiping, the endless dates, the 35-year-old men who want to get married and have kids “some day.” Look at the marriage and cohabitation rates and the number of people who aren’t married but wish they were. I don’t mean to draw a direct causal arrow from any particular change in our norms — it’s not that, for instance, an increased acceptance of premarital sex leads inexorably to the loss of “pair-bonding” technology¹² — but our norms have changed recently, rapidly, and intentionally. The last hundred years of Western culture have been one example after another of supposedly “outdated” or “pointless” social technologies kicked to the curb, and not just in the realm of marriage. It's the cultural equivalent of sequencing the human genome and immediately deciding to CRISPR out the 98% of our DNA that doesn't code for proteins.

Plenty of people see this as a victory and an emancipation: humanity freed at last from the dead hand of the past! Farewell to Wordsworth’s “meagre, stale, forbidding ways / Of custom, law, and statute” — we have it in our power to begin the world over again! I suspect this view stems from an over-application of the analytic toolbox that’s served us so well in the manipulation of our physical environment. It’s certainly related to the rapidity of change in our material circumstances (driven, of course, by that same technological prowess). But if Henrich’s model is right, and I think it is, we owe our wealth, our safety, our very teeth and skulls, to what untold generations-worth of dead hands built. Some of it will inevitably wither away as it no longer serves its purpose, but the stable families engendered by lasting pair-bonds, the high social trust created by universal application of law — these are our kayaks. Without them, nothing else can be secure, and we discard them at our peril.

1. It was also written largely to lay out the theoretical background for the argument of his second, more tendentious book, The WEIRDest People in the World: How the West Became Psychologically Peculiar and Particularly Prosperous, which I plan to review some day.

2. I personally would not expect “this guy has had sex with my wife” to incline a man towards fraternal feelings, but life is a rich tapestry. It’s also interesting to note that most of the attested polyandrous societies are in harsh, cold conditions in Tibet and usually practice a polyandry of the form “several brothers share one wife.” Convergent cultural evolution or my pareidolia? You be the judge.

3. There’s a whole book on this, which I recommend: Catching Fire: How Cooking Made Us Human, by Richard Wrangham. Henrich cites it too.

4. I know I said I was going to leave out all the psych lab stuff, but one study was too funny not to include: some Germans got a bunch of fourteen-month-olds in a lab and let them watch a man interact with his shoes. In some cases he acted confused and ultimately put the shoes on his hands, while with other babies he acted normally and put them on his feet. Then he brought out a large button, put it on the table in front of him, and used his forehead to press it, making it light up. Babies who had seen him interact competently with his shoes were twice as likely to copy his novel button-pushing method as babies who had seen him flail. The methods section of this article includes the line “An additional 9 infants were tested but not included in the final sample due to fussiness,” which I think is just delightful.

5. Parallel cousins are your mother’s sister’s (or father’s brother’s) children; cross cousins are your mother’s brother’s (or father’s sister’s). The Melanesians of Fiji, among others, count this going back several generations and prescribe specific social roles for your great-grandmother’s sister’s great-grandchildren as compared to her brother’s great-grandchildren.

6. I realize that many of my examples are about food; this is partly because I’m interested in food, but also in large part because obtaining sufficient calories was the central feature of human life for almost all of our history.

7. The Tasmanians are not unique in losing the ability to make fire; the people of the Andaman Islands, the Sirionó of Bolivia, and the Northern Aché of Brazil also lost that technology.

8. That bit about women towing the rafts seemed weird, right? From Sick Societies:

…men clearly dominated women and benefited disproportionately from their labor and risk. Yet with the possible exception of spearing kangaroos and wallabies, a task at which men arguably would be more efficient than women, either sex could, in principle, have carried out any of the necessary subsistence activities. In reality, however, almost all of these activities, including the potentially most dangerous ones, fell exclusively or primarily to women. While men often remained in camp resting or talking (early European observers called them “indolent”), women fetched water and firewood and gathered vegetable products. They alone collected shellfish, the dietary staple, by diving deep into coastal waters where sharp rocks, unpredictable currents, and stingrays were common hazards. More remarkable still, the job of climbing eucalyptus trees (to a heigh of as much as ninety feet!) to club possums to death also fell to women. And it was women who swam and crept up on sleeping seals to club them to death.

It is likely that Tasmanian women took more risks in the food quest than women have in any other folk society. Conversely, men took virtually no risks in their subsistence activities. For example, men appear to have excluded women from hunting kangaroos and wallabies not because this activity was dangerous, but because to them hunting was enjoyable while other forms of foraging were not. Despite the risks that women took and their crucial role in the economy, Tasmanian women appear to have been treated harshly by men and to have been denied access to the choicest foods. That Tasmanian women were not content with their lot was evident from the fact that they frequently complained to early European visitors about their husbands’ mistreatment of them. It is true that this Tasmanian economic system functioned well enough to maintain the population at a more or less steady state, but a set of food-getting practices that exposed women to so many hazards while men contributed so little would hardly seem to be optimal, especially not if, as was the case, women were disaffected as a result and the population nearly starved every winter.

9. I haven’t been able to find a follow-up on this. I would guess that eventually the experimental group returned to the same level of lateness as the control group, since punctuality norms didn’t vanish from all of society and would probably “leak” back into their daycare pickup behavior, but I would be fascinated to know how long it took.

10. I know, I know.

11. A refresher on the rules: it must be conducted by a third party known to both, and the lower-ranking individual must be introduced to the higher, as in “Mr. Musk, may I introduce Dril? Dril is a pseudonymous poster on your platform.”

12. Not least because rates of premarital sex have varied enormously over human history, and in plenty of cases premarital sex actually functioned as part of the society’s marriage practices.