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The Secret of Our Success

How Culture Is Driving Human Evolution

Joseph Henrich

More books on Evolution

If you dropped a tribe of African monkeys and a similar sized group of humans into a novel South American jungle, saf c any tools or equipment, who do you think would survive best? Despite our big brain, we would be at a big disadvantage. When modern Euro explorers got trapped in undeveloped areas, they either died or were rescued by indigenous people who knew the local tricks/skills needed to survive there.

Two of most basic changes are the enlarged brain needed to store all the cultural info needed to survive, and the longer post-menopausal lives that gave opportunity to pass on the info.

Ants have colonised a wide variety of environments, but they have done so by splitting into at least 14,000 different species, with multiple genetic adaptations which enable them to exploit those environments. Humans remain a single species showing relatively little genetic variation, yet have settled into many different environments. Chimpanzees, in contrast, remain confined to a narrow band of tropical African forest and have split into three distinct subspecies.

So what makes us special? Common suggestions:

1. Our big brains give us more smarts to figure out solutions to problems.

2. We are good at co-operating

While both of these are true, don't recognize the intense reliance we have on a large body culturally transmitted info that no single individual or group could figure out in a lifetime.

Concorde or Sunk Cost fallacy - we keep watching a crap movie bc paid for it, even though we know we'd be happier doing something else, such as sleeping.

People preferentially learn from those who speak their dialect. A German infant will choose a difficult technique (such as turning on a table lamp with your head) if he sees it demonstrated by another German speaker, rather than an easy way (use your hand) demoed by a Russian. This has multiple implications, both personal and genetic. First, implies that students will learn most easily from a teacher who matches them most closely. Second, implies that there is an underlying genetic factor to our preferences - an infant hasn't had time to absorb parental prejudices.

Celebrity suicides cause a spike in copy-cat suicides. Those who kill themselves tend to match the celebrity in age, sex and ethnicity. We know they are imitating bc they choose the same method. And they are definitely not suicides which would have happened anyway, bc then there would be a dip in suicide rates afterwards.

Chimpanzees can get enough calories to sustain themselves immediately after infancy - about 5 yo. Humans only reach that at about 18 (in hunter-gatherer communities) and although reaching peak fitness and strength by mid twenties, hunting ability doesn't peak until mid forties, bc it depends more on know-how and refined skills than physical prowess.

Don't try to wrestle even a young chimp. The only contests you're likely to win are threading a needle, throwing a baseball pitch or long-distance running. Humans can run down antelope, giraffes, deer, zebras, wildebeest - they eventually drop either from fatigue or heat exhaustion. Today's horses can keep up with us bc we've bred them for endurance. Wild dogs and wolves can keep up, but only at dawn or dusk. When it gets hot, the dogs flake out.

This is partly bc we have a host of skeletal adaptions (long legs, reinforced joints, muscles to support torso and head while running) but also bc we have unparalleled heat loss mechanism - we have lot more sweat glands particularly on head and feet.

But there is one necessary component that is culturally determined, not physically. Without water, we couldn't sustain an extended chase, but human are poor water storers. We get round that by developing water carriers and by becoming expert at finding local water, and by passing that expertise down to children.

Blue or green eyes are a side effect of the adaptation of lighter skill to maximise Vit D absorption.

Agriculture and alcohol go together. Hunter-gatherers don't have the resources (cereals) but almost every agricultural community, no matter how small, does.

Spices are antimicrobe and antibacteria. People come to enjoy the experience of eating chili peppers mainly by reinterpreting the pain as excitement.

Prestige: people copy others that have the skills their culture values. And when they are first learning, they are not sure who to copy, so they check who their elders are deferring to. They are often unsure of exactly what makes that person successful, so they copy everything, just in case.

We see the impact of this with celebrity endorsements. It's unclear why a sportsman with no academic qualifications has a valid opinion on insurance, or what sort of car to drive etc. Yet educational campaigns or articles on medical findings have little impact. Angela Jolie reveals that she has had a double mastectomy bc she carries a faulty BRCA1 gene, and clinics worldwide are flooded with women wanting a genetic screen.

Dominance is other source of social status. Control others through force or threat, whereas prestige is about willing co-operation.

Every traditional society reveres older members bc they are repository of accumulated cultural wisdom. Animals, with no culture, do not behave same way.

Capt Cook first long voyage to S Pacific 1768. For centuries the RN had been plagued by scurvy, caused by Vit C deficiency. Cook was advised to take a large supply of sauerkraut, but the problem was to get his crew to eat this foreign, strange smelling material. So he ordered it served only to the officers. Within a week the crew were demanding that they be given a share of it. It got so popular it had to be rationed. Cook finished his expedition without a single death to scurvy, a feat unheard of in European fleets making long voyages.

Social norms make it possible for humans to solve difficult social dilemmas. Social life is riddled with chances to exploit others. But society has ways to reduce that, first by 3rd party monitors (gossips) to publicize transgressors, and second by providing models of what is good and bad.

And these models can shift. Behaviours such as smoking, eating horse meat and littering have all gone from perfectly acceptable to disgusting in a couple of generations.

Aché tribe sequential marriages. Divorce initiated by either partner simply moving out. By age of 30 most women had had average of 10 marriages. All first marriages ended. Although polygamous marriages uncommon, every woman had been in one at some point. Some men serially married and had children with, 3 sisters. Some women married both father and son, at different times, and men married mother and daughter.

Four societies in Yunnan and Sichuan provinces in China have maintained female-headed households for millennia. Men slip into women's houses for sex and are gone by morning. Child paternity is often uncertain and fathers don't contribute directly to households. They have no words for 'father' or 'husband'. There are no social norms regulating fidelity or marital-type obligations.

Common S American belief that a single injection of sperm is not enough to form a healthy baby - need regular, multiple injections, and from other men, who become secondary fathers, with an obligation (though less than primary father) to deliver food to the baby's household. Often the secondary fathers are brothers of main father. So even though father may be jealous of wife's other lovers, restrained by the society's approval of the mother seeking backup parents.

Chatting alone, in most societies, is often an impt first step toward sex.

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