The Secret of our Success: How Culture is Driving Human Evolution, Domesticating our Species and Making us Smarter

Joseph Henrich (2001)

In a paragraph

The secret of humanity’s success is cumulative cultural evolution.  Cultural evolution has been the primary driver of our species’ genetic evolution. Larger and more interconnected populations generate more sophisticated tools, techniques, weapons, and know-how because they have larger collective brains.

Key points

• The secret of our species’ success resides not in the power of our individual minds, but in the collective brains of our communities.

• We don’t have 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.

• By “culture” I mean 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. We are a cultural species.

• Like natural selection, our cultural learning abilities give rise to “dumb” processes that can, operating over generations, produce practices that are smarter than any individual or even group. The process of cumulative cultural evolution

• Lost European explorers failed to survive unless helped by locals.

• 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.

• Specialized distance running adaptations – the sweatiest species.

• Cultural evolution is often much smarter than we are. Faith in cultural inheritance. Humans evolved a dependence on cultural know-how just to eat.

• We look to prestigious models for learning. Age is only a good proxy if the world faced by the new generation is pretty similar to that faced by the oldest generation.

• Our social instincts are harnessed, magnified, and recombined within an interlocking web of culturally evolved social norms.

• Marriage norms can buttress spousal relationships and create affinal (in-law) relationships. The evolution of in-laws may be one of the key features that make humans special.

• The sanctions for norm violations and the rewards for norm compliance have driven a process of self-domestication that has endowed our species with a norm psychology that has several components. Humans intuitively assume that the social world is rule governed, when we learn norms, we, at least partially, internalize them as goals in themselves and internalizations may provide a quick and efficient heuristic.

• 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. Ultimatum Game.

• Our minds are prepared to carve the social world into ethnic groups.

• Larger and more interconnected populations generate more sophisticated tools, techniques, weapons, and know-how because they have larger collective brains. Fire, pottery and ocean travel were learnt and lost. The wheel is recent.  Cultural poverty of Tasmania and Polar Intuit. Eurasia’s advantage. Global community and internet.

• Languages co-evolve with culture. Vocabulary, colours, numbers, subordination.  Valuable concepts.

• Cultural differences are biological differences but not genetic differences. Growing up in a culturally constructed environment shapes our bodies and brains over development nongenetically. At the most basic level, cultural learning shapes the reward circuitry in our brains so that we come to like and want different things. Honour cultures. Frame dependence.

• 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. Understanding how this major transition is occurring alters how we think about the origins of our species, about the reasons for our immense ecological success, and about the uniqueness of our place in nature.

Comments

A high-quality, wide-ranging and absorbing statement of the view that culture is central to human evolution and to understanding human nature.  The main thesis is convincingly demonstrated, and numerous fascinating aspects are covered.   

Links

A good summary of Joe Henrich’s thinking is this warm and well-structured conversation on the Jolly Swagman podcast.

This is a link to the book at amazon uk.  I also enjoyed the audiobook.

Notes

Preface

Reading year. I had developed a murky vision for what I wanted to do. An evolutionary theory of human nature.

People are automatic cultural learners, that we follow social norms, and that the cultural worlds we grow up in influence what we attend to, perceive, process, and value.

Rob Boyd, collective brain.

1. A Puzzling Primate

You and I are members of a rather peculiar species, a puzzling primate.

Suppose we took you and forty-nine of your co-workers and pitted you in a game of Survivor against a troop of fifty capuchin monkeys from Costa Rica.

An addiction to culture.  By “culture” I mean 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.  We are a cultural species. Culture became cumulative.

Natural selection had to favour individuals who were better cultural learners. Culture-gene coevolution. A novel evolutionary pathway not observed elsewhere in nature, a new kind of animal.

Culture evolves, often invisibly, as these selective attentions and learning biases shape what each person attends to, remembers, and passes on.  These cultural learning abilities gave rise to an interaction between an accumulating body of cultural information and genetic evolution that has shaped, and continues to shape, our anatomy, physiology, and psychology.

The extended childhoods and long postmenopausal lives that give us the time to acquire all this know-how and the chance to pass it on.

We now often put greater faith in what we learn from our communities than in our own personal experiences or innate intuitions.  A second form of human status, called prestige, which now operates alongside the dominance status we inherited from our ape ancestors.

Social norms. Self-domestication, prosocial, docile, rule followers.

The secret of our species’ success resides not in the power of our individual minds, but in the collective brains of our communities.

Innovation in our species depends more on our sociality than on our intellect.

Languages are products of cultural evolution.

Received a massive cultural download while growing up that included a convenient base-10 counting system.

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.

2. It’s Not Our Intelligence

The megafauna of Africa, and to a lesser extent of Eurasia, fared much better, probably because these species had long coevolved over hundreds of thousands of years with humans

It’s not just the fault of industrialized societies; our species’ ecological impacts have a deep history.

The manner in which we adapt to diverse environments, and why we thrive in so many different ecologies, does not arise from an array of environment-specific genetic adaptations, as with most species.

Smarter and more flexible “not because we have fewer instincts than other animals; it is because we have more.”

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.  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.

The crucial selection pressure was us.  Our ability to acquire, store, organize, and retransmit an ever-growing body of cultural information.

Like natural selection, our cultural learning abilities give rise to “dumb” processes that can, operating over generations, produce practices that are smarter than any individual or even group.

Social learning. Individual learning. Cultural learning.

The humans did not obviously dominate their fellow apes on either working memory or information processing speed, despite our much larger brains.

Machiavellian intelligence hypothesis.

Matching Pennies. Matcher. Mismatched.

3. Lost European Explorers

King William Island. Robert Burke. Nardoo. San Nicolas Island.

4. How to Make a Cultural Species

Aggregate to produce cultural adaptations.

Culture and the Evolutionary Process, Rob Boyd and Pete Richerson

Whom to learn from? Conformist transmission. the wisdom of crowds is built into our psychology.

When celebrities commit suicide there is a spike in suicide rates. Suicide epidemics. We can acquire practices via cultural learning that natural selection has directly acted to eliminate under most conditions.

Mentalizing, or theory of mind. Mentalizing abilities begin to develop early and reliably across diverse human societies.

Teaching is the flip side of cultural learning.

Cultural learning may have initially developed as a response to the enriched environments created by the very earliest accumulations of cultural evolution.

5. What Are Big Brains For? Or, How Culture Stole Our Guts

By selectively attending to certain types of cultural content, like food, sex, and tools, and to particular models based on cues related to prestige, success, and health, individuals can most efficiently equip themselves with the best available cultural know-how.

When the MBAs were allowed to copy each other — the whole group gradually zeroed in on the optimal investment allocation.

Cumulative cultural evolution

“Savannah hunting package”.

Occasional insights and lucky errors were preferentially passed on

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.

Autocatalytic, meaning that it produces the fuel that propels it.

Big-headed baby problem. Myelination.

Food Processing Externalizes Digestion. Our small intestines are about the right size for a primate of our stature. Our bodies have been shaped by fire and cooking, but we have to learn from others how to make fire and cook.

The emergence of tools and weapons allowed natural selection to trade expensive tissues for fat, which is cheaper to maintain and provides an energy-storage system crucial for sustaining big brains through periods of scarcity.

Fine dexterity

Learning psychology. Categorize “artifacts.

Specialized distance running adaptations. Springy arches. Longer legs. Springlike tendons, including the crucial Achilles, that connect to short muscle fibres. Unlike animals built for speed, which possess mostly fast-twitch muscle fibres, frequent distance running can shift the balance in our legs upward from 50 % slow-twitch muscle fibers to as high as 80 %, yielding much greater aerobic capacity. Joints in our lower body are all reinforced. To stabilize our trunk while running, our species sports a distinctively enlarged gluteus maximus. Arm swinging nuchal ligament, connecting our heads and shoulders, secures and balances our skulls and brains against running-related shocks. The sweatiest species. The (1) nearly complete loss of hair, (2) proliferation of eccrine sweat glands, and (3) emergence of a “head-cooling” system. Sweat glands come in two varieties, apocrine and eccrine. Scalp and feet. Brain cooling system. Veins that run near the surface of the skull, where they are first cooled by the ample sweat glands on the face and head. They then flow into the sinus cavities, where they absorb heat from the arteries responsible for transporting blood to the brain. Panting.

Cultural evolution supplied water containers and water-finding know-how. Hunters force their prey into a series of sprints and rests that eventually result in heat stroke. Nonhuman predators tend to follow the herd, not the loners, since they rely on scent.

Essentialized categories. Hierarchical (treelike) taxonomies. Category-based induction. Taxonomic inheritance.

6. Why Some People Have Blue Eyes

Melanin. Folate. Vitamin D. Baltic.

Lactose tolerance: one of the African variants may be the oldest, with the European variants in the middle, dating to between 7450 and 10,250 years ago. The variant cantered in the Arabian Peninsula is probably more recent, between 2000 and 5000 years old.

Post marital residence, patrilocal residence, matrilocal residence.

7. On the Origin of Faith

Manioc (or cassava). Cyanide.

Causally opaque. Cultural evolution is often much smarter than we are. Faith in cultural inheritance

Ciguatera toxin. To release this niacin, populations throughout the New World culturally evolved practices that introduced an alkali (a base) into their corn preparations. stops pellagra

The list of “natural” foods that need processing to detoxify them goes on and on.

Humans, however, lost these genetic adaptations and evolved a dependence on cultural know-how, just to eat.

Bird augury.  Sometimes it may even be important that they don’t understand what their practices are doing or how they work.

Over imitation. Until recently, cumulative cultural evolution drove the emergence of deeper causal understandings much more than causal understanding drove cultural evolution.

Since the rise of cumulative cultural evolution, natural selection has lost its status as the only “dumb” process capable of creating complex adaptations. Cultural evolution is smarter than we are.

8. Prestige, Dominance, and Menopause

Rob Hall at Everest Base Camp. Two quite distinct forms of social status, dominance and prestige.

The group had been saved by their ritual songs and by the distant memories of an old man.

Age is only a good proxy if the world faced by the new generation is pretty similar to that faced by the oldest generation.

Killer whales. Older elephant matriarchs.

Sauerkraut against scurvy.

9. In-Laws, Incest Taboos, and Rituals

“Classificatory sisters,” parallel cousins, cross-cousins.

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.

Our social instincts are harnessed, magnified, and recombined within an interlocking web of culturally evolved social norms.

Marriage norms can buttress spousal relationships and create affinal (in-law) relationships. “pair-bonding” is often confused with notions of monogamy.

Paternity certainty. The mother’s husband — has the privilege of naming the child.

Divorce was initiated unilaterally by either party or involved simply moving out, which was easy since the Ache didn’t have much stuff.

Genetic fathers are not expected to contribute to the child’s household; instead, men invest in their sister’s children. “additional fathers”

Human communities — whom we ally with, help, marry, and love — are forged by social norms, which variously harness, extend, and suppress our social instincts.

Marriage norms create over half the ties in adult relationships within a band.  The evolution of in-laws may be one of the key features that make humans special.

Cultural-institutional technologies like ownership transfer and meat taboos operate to make sharing psychologically easier. 

Ritual and affinal relationships, both of which are culturally constructed and non-existent in primates or other animals, explain much more about the patterns of association, cooperation, helping, and sharing than blood ties.

10. Intergroup Competition Shapes Cultural Evolution

Intergroup competition provides one important process that can help explain the spread of norms that foster pro sociality.

War and raiding. Differential group survival without conflict. Differential migration. Differential reproduction. Prestige-biased group transmission.

Hostility usually occurred between tribal populations, which consisted of many interlinked bands who shared customs and language, rather than between residential groups, as in chimpanzees.

The Puma-Nyunga expansion began in north-western Queensland between 3000 and 5000 years ago and gradually spread over most of the continent.  Around 1000 CE, speakers of an Inuit-Inupiaq language — the Inuit — began expanding eastward across the vast Canadian Arctic, supplanting the Dorset Eskimo. Around 60,000 years ago, groups of Homo sapiens expanded out of Africa.

11. Self-Domestication

The sanctions for norm violations and the rewards for norm compliance have driven a process of self-domestication that has endowed our species with a norm psychology that has several components. Humans intuitively assume that the social world is rule governed.  When we learn norms, we, at least partially, internalize them as goals in themselves.  Internalizations may provide a quick and efficient heuristic

Ultimatum Game. Public Goods Game.

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.

Violating a social norm requires mental effort and “higher” cognition.

Kiley Hamlin: babies prefer puppets who hurt previously antisocial persons.

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.

The importance of language as an ethnic marker.  Head flattening. Norm boundaries are often marked by language, dialect, dress, or other markers (e.g., head shape).

Our minds are prepared to carve the social world into ethnic groups, but not into classes or ideologies.  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 colour or hair form, which are genetically transmitted.

If war is experienced during this age range, it sharpens people’s motivations to adhere to their egalitarian norms, but only for their in-groups.

12. Our Collective Brains

It’s better to be social than smart. Larger populations had more-complex technologies.  Larger and more interconnected populations generate more sophisticated tools, techniques, weapons, and know-how because they have larger collective brains.

If a population suddenly shrinks or gets socially disconnected, it can actually lose adaptive cultural information,

Tasmanians slung wallaby skins over their shoulders and applied grease to their exposed skin.  They did not catch or eat any fish.  The Tasmanian toolkit consisted of only about twenty-four items. Tasmania was connected to the rest of Australia until about 12,000 years ago.

They had larger collective brains capable of generating greater cumulative cultural evolution.

It’s plausible that the Neanderthal replacement may have been just an earlier chapter in a cultural evolutionary story.

Like ocean-going boats and pottery, it turns out that the know-how to make and use bows and arrows is frequently lost by human groups. As previously noted, some foraging groups have even lost the know-how for starting a fire.

The wheel was invented relatively late in human history, long after agriculture and dense populations had emerged, and only in Eurasia. It was never invented in the Americas, Australia, or New Guinea.

Ready concepts to apply to somewhat new problems. Cognitive tools or mental abilities that we would otherwise not have.

In doing mental arithmetic both Western undergraduates and abacus users had to rely on the products of cumulative cultural evolution.

13. Communicative Tools with Rules

Non-speech elements of our repertoires. Plains Indian Standard Sign Language. Whistle languages. Sonority.

Small-scale societies contain between 3,000 to 5,000 words.  The full-size Oxford English Dictionary contains more than 300,000 entries. The average American 17-year- old knows 40 – 60,000 words while their professors know about 73,000 words.

Languages vary in their number of basic colour terms. At one end of the spectrum, English has 11 basic terms.  Many languages have no basic colour terms, or only two, which are always “black” and “white”. Numerous languages have 5 colour terms, which can be glossed as “white,” “black,” “red,” “yellow,” and “green-blue” (grue).  The Old Testament, the works of Homer, and ancient Vedic poems are remarkably vague about colour and at times devoid of colourful descriptions.

To our knowledge, all societies have number words for 1, 2, and many, and numerous societies count “1,” “2,” “3,” “many” — but that’s it; they can’t count any higher.

Words are useful for thinking, so possessing a large vocabulary likely improves some kinds of problem solving.

American adults score higher on IQ tests than their parents or grandparents did at the same age, in part, because they have learned to use and understand more words.  We should expect the vocabulary sizes of languages to expand with a population’s collective brain.

Hawaiian has 5 vowels but combines them with 8 consonants. English has roughly 24 consonants and at least 12 vowel sounds, depending on the dialect. ! Xóõ speakers use roughly 47 non-click consonants and 78 click sounds and have a sound inventory of over 140 sounds. Languages with more speakers tend to have more sounds. Languages with more phonemes in their inventories tend to have shorter words.

Subordinating conjunctions, like “after,” “before,” and “because of,” may have evolved only recently.  The tools of subordination seem less well developed in the earliest versions of Sumerian, Akkadian, Hittite, and Greek. This makes these languages slow, ponderous, and repetitious to read.

Modern world languages may in fact be rather unusual.  Lost out in competition to more learnable languages. Regularity makes languages more learnable.

Communicative systems, were coevolving with tools, practices, and social norms. Both language and tools (manual actions) involve overlapping brain regions. Language probably arrived on the scene well after cultural evolution was underway and had already assembled simple communicative repertoires.

14. Enculturated Brains and Honourable Hormones

High levels of literacy improve some cognitive abilities.  Skilled readers are probably worse at identifying faces.  Children are never taught that letter size is irrelevant; they automatically know or infer this rule.

Cultural differences are biological differences but not genetic differences. Growing up in a culturally constructed environment shapes our bodies and brains over development nongenetically. At the most basic level, cultural learning shapes the reward circuitry in our brains so that we come to like and want different things.

People rated the more expensive wines as better (more pleasurable), even though they were actually exactly the same wine.  Americans without wine training prefer wines that are actually less expensive.

Modifying the Hippocampus by Driving in London

Westerners are less “frame dependent”

“Honour cultures”

Placebos.  Chemically inert but biologically active.

It Hurts So Good.  Runners like me enjoy running,“tough-model”

Numerous medical treatments (which are purely placebo effects) and witchcraft often actually work and cause important biological effects.

15. When We Crossed the Rubicon

Our last common ancestor with chimpanzees who lived 5 to 10 million years ago had not crossed the threshold to cumulative cultural evolution.

4 million years ago, walked on two legs.  Austral piths. 2.6 million years ago, Oldowan tools. 2.4 million years ago, Early Homo. 90 % of these toolmakers were right-handed. Dancing on the threshold of cumulative cultural evolution. We shouldn’t expect a continuous trend toward greater complexity over time.

1.8 million years ago, Homo erectus. Good evidence of both cooking and fire at around 800,000 years ago. “blanks,” a throwing tradition.  The site of Gusher Benot Ya’aqov has yielded rich insights into the life of one society around 750,000 years ago. Homo Heidelbergensis.

Cumulative cultural evolution is old in our species’ lineage, dating back at least hundreds of thousands of years, but probably millions of years.

16. Why Us?

Start-up problem. A large ground-dwelling primate. When they descend from the trees to the ground, the possibilities created by having hands open up.

Predation favours the evolution of larger, less diffuse groups which in turn favours the spread of a pair-bonding strategy. The increased density of individuals and the social inheritance of local knowledge.

Alloparental care.  How dependent humans are on cultural learning for what should be basic mammalian functions. Colostrum.

17. A New Kind of Animal

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

Understanding how this major transition is occurring alters how we think about the origins of our species, about the reasons for our immense ecological success, and about the uniqueness of our place in nature.

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.

The central force driving human genetic evolution for hundreds of thousands of years, or longer, has been cultural evolution.

Many aspects of our physiology and anatomy make sense only as genetically evolved responses to selective pressures created by the cultural evolution of things.  Many of our cognitive abilities and biases make sense only as genetically evolved adaptations to the presence of valuable cultural information

Trying to understand the evolution of human anatomy, physiology, and psychology without considering culture-gene coevolution would be like studying the evolution of fish while ignoring the fact that fish live, and evolved, underwater.

To better understand human life, we need to embrace a new kind of evolutionary science, one that focuses on the rich interaction and coevolution of psychology, culture, biology, history, and genes.