Evolutionary mismatch, system by system
Evolutionary mismatch examples in humans: 42 body systems, graded
Each row is one mismatch card: what a part of the body evolved to expect, what modern life gives it instead, and what happens in the gap, with the grade the book gives the evidence. The words in the table are the cards' own.
Published Updated
| System | What it evolved to expect | What it gets now | What happens in the gap | Grade | Read more |
|---|---|---|---|---|---|
| Chapter 2The whole body, read on three clocks: genes over generations, development over a lifetime, physiology over days and weeks. | The signals its long past supplied without anyone arranging them: hours on foot, real darkness, varied food, microbes, heat and cold, and familiar people close by. | Too little of some signals (movement, daylight, fiber, company), too much of others (sugar, salt, evening light), and exposures that are new (nicotine is the classic example). | Many chronic diseases are suspected mismatches, graded chapter by chapter; local genetic tuning means the gap differs from person to person. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 2: What Your Body Expects, and How to Trust This Book |
| Chapter 3The walking body: leg muscles and joints, heart and blood vessels, lymph, back and feet. | Hours on foot most days, rest in squats and on the ground, little salt and plenty of potassium, and use of a sore body while it heals. | Nearly eight sedentary hours a day and about 5,100 steps for the average American, about 11 g of salt a day worldwide, and rest, scans and fear after injury. | Higher blood sugar within hours of sitting, blood pressure that climbs with age, knee arthritis in American skeletons that has doubled beyond what age and weight explain, and back pain that hardens into disability. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 3: The Body That WalksTopic 6: The Sitting Disease |
| Chapter 4Skeletal muscle and bone, which calibrate their strength to the loads they carry. | Daily walking, carrying and lifting, often heavy, across a whole life. | Chairs, wheels and machines; little that is heavy; and, for women, a menopausal transition that speeds bone loss with no extra load to answer it. | Strength falls faster than size, bone thins where load is missing, and the losses show up decades later as weakness, falls and fractures. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 4: Load, Strength and Bone |
| Chapter 5Appetite and fuel: the gut, liver, muscle and fat, and the reward circuits that steer eating. | Food that took work to get and time to chew, sugar wrapped in fiber, alcohol at a fraction of a percent, and water when thirsty. | More than half its calories from ultra-processed food, sugar and alcohol in concentrated drinks, and little physical work. | People eat more without trying, surplus fat overflows into the liver and muscle, and diabetes climbs, as it did along the Gila. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 5: EatTopic 13: The Thrifty Body |
| Chapter 6The gut's microbes and the immune system's learned tolerance. | Tens of grams of fiber a day from many plants; microbes from siblings, animals, soil and food; early tastes of lifelong foods; fever and care while sick. | About 17 g of fiber a day (the US adult average), small families and indoor lives, needless antibiotics, delayed allergenic foods until recently, and fear of the thermometer. | Fewer gut species, more allergy, autoimmune disease diagnosed in about one person in ten in the UK over two decades (mostly women), resistant bacteria and returning measles. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 6: The Gut That Expects DirtTopic 12: The Gut That Expects DirtTopic 18: The Immune System's Education |
| Chapter 7The circadian clock, set through melanopsin in the eye; skin pigment and vitamin D; the growing eye. | Bright days, truly dark nights, sun matched to skin and changing with the seasons, and a childhood spent largely outdoors. | Days mostly indoors under room light far dimmer than any sky, evenings lit brightly enough to hold the clock back, lit bedrooms, pale skin under sudden holiday sun and dark skin in indoor lives, and classrooms instead of fields. | The clock drifts later, sleep timing scatters, vitamin D runs low in some skins while sunburn and skin cancer rise in others, and children's eyes grow too long. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 7: Light and Dark |
| Chapter 8The circadian clock and the sleep it schedules, tuned by light, temperature and routine. | A bright day, a dark night that cools, and the same timing tomorrow; enough sleep, with room for naps. | Dim days, lit evenings, a bedroom at one temperature with a phone in it, a schedule that lurches at weekends, afternoon caffeine, and for some, work through the night. | Sleep moves later and grows irregular; insomnia is common and often untreated; night workers live against their own clocks; apnea goes undiagnosed, especially in women after menopause. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 8: SleepTopic 23: Sleep and the Dark You Have Lost |
| Chapter 9Thermoregulation: skin blood flow, shivering muscle, brown fat, sweating and the heart's response to heat. | Days and seasons that leave the comfortable band: cool mornings, warm afternoons, nights that cool, and occasional real cold and real heat. | A narrow indoor band all year, most of life spent inside, offices set for a man in a suit, and summers whose humid heat can outrun the body's cooling. | Cold acclimatization fades within a few years of the signal stopping, as the haenyeo showed, though the metabolic cost appears small, and a body that rarely meets heat has had no practice at shedding it. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 9: Heat and ColdTopic 25: The Thermoneutral Trap |
| Chapter 10The stress system, attention and the heart, tuned by a living landscape; hearing, and the threat circuit it feeds. | Daylight hours among plants, water and animals, and a quiet natural background broken by occasional sounds worth noticing. | Most of life indoors, a view of a wall, and mechanical noise that never stops, including at night, with bursts loud enough to damage the ear. | Slower stress recovery, more psychiatric diagnoses among children raised in the least green places, extra heart and lung deaths where the trees go, broken sleep, and avoidable hearing loss on a population scale. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 10: Green and QuietTopic 27: The Green PrescriptionTopic 26: The Ear in the Silent Room |
| Chapter 11The social brain and the stress physiology it regulates, from the threat circuitry that registers exclusion to the hormones that respond to touch. | Daily, face-to-face contact with a small, stable group; touch as an ordinary event; many hands around every infant, from labor onward. | A wide, thin network through a screen, inner circles left to chance, labor attended by rotating staff, and new parents largely alone behind a closed door. | Higher mortality among isolated and lonely people across dozens of cohorts, loneliness and depression in new parents, and a stress system that loses one of its regulators. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 11: The Social AnimalTopic 29: The Social Animal in Solitary Confinement |
| Chapter 12The reward circuit that learns from unpredictable payouts; the default network that runs during idle time; memory, navigation and reasoning that improve with use; and a child's play-driven development. | Rewards that are earned, spaced and often absent; long stretches with nothing to attend to; problems solved with your own equipment; and childhood days of free, mixed-age, outdoor play. | A pocket device engineered for time on device, paying out on a variable schedule and filling every gap; tools that supply the answer before the effort starts; and childhoods with hours of screens and the risk designed out. | Checking that resists unlearning, idle minutes that vanish, work that looks better while the person doing it learns less, and afternoons a phone ban empties but does not refill. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 12: Attention in the Age of the PhoneTopic 30: The Attention Economy and the Boredom DeficitTopic 44: The Luxury Trap Accelerates |
| Chapter 13The stress response, fast adrenaline and slow cortisol, with the defensive emotions it drives: fear, anxiety and low mood. | Threats that are physical, local and short, answered with the body, among allies who help solve problems. | Uncontrollable judgment without end, low control at work, long hours, thin company and short sleep. | Alarms built to over-fire go off constantly and stop resetting; the daily cortisol rhythm flattens, tissues stop hearing it, inflammation runs on, and anxiety and low mood are common. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 13: Stress and the MindTopic 28: Stress and the Hijacked AlarmTopic 31: The Mind That Cannot Find Its Village |
| Chapter 14The reward system (dopamine-driven wanting) and the attachment systems that bond, grieve and seek a role. | Rewards that are scarce, variable and diluted; a partner and a small group met every day; losses mourned with others; a role the group depends on. | Pure, cheap, constant drugs and betting on a phone, with close relationships, mourning and purpose left to arrange themselves. | Substance use disorders in about 15 percent of Americans aged twelve and over, just over half of them mild; a rise in mortality after bereavement, sharpest in the first months and in men; higher mortality with low purpose in cohorts. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 14: Wanting, Loving, Losing, MeaningTopic 11: The Hijacked Reward System |
| Chapter 15The female reproductive axis across a lifetime, from first period through pregnancy to the transition and the decades after it. | A first period in the mid-teens, many pregnancies with long breastfeeding between them and about a hundred periods in a lifetime, food that matches effort, kin nearby, and a working body that carries loads through the transition. | Earlier first periods, fewer and later births, short breastfeeding and about four hundred periods; energy deficits in some and surpluses in others; grandmothers far away; and a transition lived mostly sitting down. | More hormone-driven cancers and more iron lost; periods that stop from low energy; common conditions such as PCOS and endometriosis diagnosed late; symptoms of the transition endured instead of treated; bone and muscle lost fastest just as loading falls. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 15: Women's Bodies Across the Life Course |
| Chapter 16The whole body over a lifetime: the cells that age and occasionally turn cancerous, and the organs that fail at the end. | Daily physical work, food that comes and goes, constant company and microbes, and death arriving mostly from outside, after a modal age in the seventies. | Low physical load, constant food, tobacco and alcohol, and medicine that postpones death from diseases whose causes remain in place. | Longer lives with a wider strip of illness at the end; in the United States, the widest gap between lifespan and healthy lifespan of 183 countries studied. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Chapter 16: Aging WellTopic 35: The Hallmarks of AgingTopic 36: Why We Die the Way We Do |
| Topic 1The mammalian operating system: warm blood, night-built senses, milk, late-added color vision. | High energy costs paid for by effortful foraging; real darkness at night; changing temperatures; food judged by color and smell. | Abundant calories, climate-controlled rooms, bright evenings, engineered food colors. | Sleep and light (Topic 23), temperature (Topic 25), food reward (Topic 11); even the body's thermostat is drifting, for unknown reasons. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 1: The 200-Million-Year Warm-UpIn the book: Chapter 2, What Your Body Expects, and How to Trust This Book |
| Topic 2The upright, running, sweating body: spine, knees, springy tendons and sweat glands. | Kilometers of walking most days, some running, carrying and throwing, and warm air that sweat can cool. | Chairs, cars and desks; nearly a third of adults worldwide below minimum activity. | Built-in weak points meet modern ways of loading, moving and weighing: low back pain is the world's leading cause of years lived with disability, and knee osteoarthritis in the United States has doubled beyond what age and weight explain. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 2: Standing UpIn the book: Chapter 3, The Body That Walks |
| Topic 3The brain and the mental habits it runs. | Cooked, varied food; sleep; a band of about 30 people inside a wider network; daily physical and mental challenge. | Long hours seated (Topic 6), isolation for some, and prices, deadlines and risks its defaults never met. | Defaults misfire as worry, the planning fallacy and reluctance to part with what you own; isolation and inactivity are associated with smaller brain structures and higher dementia risk. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 3: The Expensive OrganIn the book: Chapter 5, Eat |
| Topic 4The agricultural body: a forager's physiology, partly retuned since farming began. | A varied diet of wild plants and animals, daily walking and carrying, small mobile groups, seasonal variety. | Cereals supplying 42% of the world's dietary energy, sedentary work, and dense settlements shared with animals and strangers. | In early farmers, on average: shorter stature, more tooth decay and infection, heavy repetitive labor. Since then, immune genes have been retuned against new pathogens, possibly at the cost of more inflammatory and autoimmune risk. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 4: The Last Ice Age and the Birth of AgricultureIn the book: Chapter 2, What Your Body Expects, and How to Trust This Book |
| Topic 7The foot, a sensing, spring-loaded base for walking, running and balance. | Bare or thinly shod feet on varied ground, working the arch and toes daily. | Cushioned, arch-supported, toe-sprung shoes on flat floors from early childhood. | Less ground feel, softened impacts of unknown cost, likely weaker foot muscles and, in some studies, flatter arches; in old age, weak toes and poor balance are linked to falls. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 7: The Foot That Forgot the GroundIn the book: Chapter 3, The Body That Walks |
| Topic 8The heart and blood vessels, a pump built to move large volumes of blood for hours. | Hours of light and moderate activity daily, little salt, plenty of potassium, a lean body and low LDL for life. | Long sitting, about 11 g of salt a day on the global average, too little potassium, abundant food. | Blood pressure that climbs with age, earlier and commoner atherosclerosis, a lower aerobic ceiling; 1.4 billion adults aged 30 to 79 with hypertension. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 8: The Heart That Remembers the SavannaIn the book: Chapter 3, The Body That Walks |
| Topic 9The lymphatic system: self-pumping vessels, 500 to 600 nodes, drains around the brain. | Kilometers of walking a day, shifting postures, regular nights of sleep. | Unbroken sitting, long-haul seats, short nights and, for some, severe obesity. | Swollen feet, more clots on long journeys, lymphatic failure at very high BMI; after sleep loss, amyloid rises of uncertain meaning. | EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested. | Topic 9: The Invisible RiverIn the book: Chapter 3, The Body That Walks |
| Topic 10Breathing: the nose as the default airway, and the breath as a lever on heart rhythm. | An open nose at rest and in sleep, with the mouth joining in for hard effort. | Noses often blocked by allergy, which pushes breathing to the mouth, and breathing hacks that outpace their trials. | When the mouth takes over in sleep, the throat collapses more easily: snoring, apneas and oxygen dips. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 10: The Breath You Forgot How to TakeIn the book: Chapter 13, Stress and the Mind |
| Topic 14The liver, first stop for most of what the gut absorbs: chemical defense and fuel storage. | Daily plant defense chemicals, occasional natural toxins such as aflatoxin, and food energy that took work to get. | Surplus calories from sugary drinks and alcohol, and more than 350,000 registered chemicals and mixtures, a few of them, such as the long-lived PFAS, beyond its power to break down. | About 30% of adults worldwide have fatty livers, and more of them die of heart disease than of liver disease; the main PFAS linger for years in nearly every American's blood. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 14: The Liver and the Chemical CenturyIn the book: Chapter 5, Eat |
| Topic 15Taste and smell, the chemical senses that judge food and air. | Sugar wrapped in fiber, bitter and sour plants, and a nose used daily to find food and judge freshness. | Sugar dissolved in drinks at all hours, debittered crops, sweeteners, polluted air, smoke, viruses and an underused nose. | Easy sugar overconsumption, lost bitter warnings, and unnoticed smell loss linked to higher mortality. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 15: The Tongue and the NoseIn the book: Chapter 5, Eat |
| Topic 16The face, jaws, teeth and upper airway. | Hard chewing from childhood, teeth that wear flat, a clear nose, little free sugar. | Soft processed food, fork-cut mouthfuls, industrial flour and sugar, and more body weight pressing on the airway. | Jaws that fall short of their teeth (crowding, impacted wisdom teeth), retained overbites, widespread decay, and possibly, alongside weight, some sleep apnea. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 16: The Shrinking FaceIn the book: Chapter 8, Sleep |
| Topic 17Water balance: thirst, kidneys and vasopressin. | Wet food and drinking to thirst, in an ape that turns over 30% to 50% less water than its cousins, size for size. | Taps, climate control, a 1945 allowance stripped of its caveats, and a market selling hydration. | Little, for most healthy people. In long events, overdrinking can dilute blood sodium and swell the brain; thirst lags in older people and in heat. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 17: The Water You Forgot to DrinkIn the book: Chapter 5, Eat |
| Topic 19Skin: pigment shield, vitamin D factory, barrier and habitat. | Sun matched to its pigment, changing gradually with the seasons, mostly outdoors and often in shade. | Pale skin under subtropical sun, dark skin at high latitudes, indoor lives and sudden, burning doses. | Skin cancer where sun outruns pigment; low vitamin D, and at the extreme rickets, where pigment outruns sun. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 19: The Largest OrganIn the book: Chapter 7, Light and Dark |
| Topic 20Fever, sickness behavior and the defenses against infection. | Infection as the commonest threat, care from others while sick, and bands too small for crowd diseases. | Crowd and herd diseases, fever treated as the enemy, work while sick, antibiotics overused and vaccines refused. | Fever phobia and contagious presenteeism; returning measles; resistant bacteria; old genetic trade-offs meeting new viruses. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 20: The Fever and the Old EnemiesIn the book: Chapter 6, The Gut That Expects Dirt |
| Topic 21Pain, the body's protective alarm, and the opioid and endocannabinoid systems that quiet it. | Injury, then a return to use while still sore, among people who help. | Rest, scans that find "damage" in pain-free people, fear and, for a time, freely prescribed opioids. | A sensitized alarm keeps ringing after tissue heals, and ordinary pain hardens into disability. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 21: The Pain You Were Not Supposed to KeepIn the book: Chapter 3, The Body That Walks |
| Topic 22Cell division and the defenses that keep cells cooperating (tumor suppressors, DNA repair, cell suicide). | A body of ancestral size and lifespan; menarche in the mid-teens, many pregnancies, years of breastfeeding; no tobacco and little alcohol. | Longer lives; earlier menarche, fewer and later births and shorter breastfeeding (three to four times the Dogon's menstrual cycles); excess body fat; tobacco and alcohol. | More hormone-driven, obesity-related, tobacco and alcohol cancers; much of the remaining rise reflects age and closer looking. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 22: Cancer in a New EnvironmentIn the book: Chapter 16, Aging Well |
| Topic 24Emmetropization, the visual feedback loop that grows the eyeball to match its optics. | A childhood of bright outdoor light, thousands of lux for hours a day, with things to look at near and far. | Years of classrooms at a few hundred lux, and 87% of time spent inside a building. | The eye overgrows, distance blurs for good, and a stretched retina carries lifelong risk. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 24: The Indoor EyeIn the book: Chapter 7, Light and Dark |
| Topic 32The reproductive axis, from the hypothalamic pulse generator to ovaries and testes, and the post-reproductive life course built around it. | Steady energy availability, first births while fertility is at its peak, kin nearby to subsidize weaned children, and a lifetime of relatively few ovulatory cycles (Topic 22). | Energy surplus or deficit rather than balance, a mean first birth at 27.5 in the United States, grandparents in other cities, and an industrial chemical environment nobody has fully characterized. | Ovulation stops in women who look healthy, obesity disturbs the same loops from the opposite side, sperm counts and testosterone drift downward across cohorts, and the biological window opens and closes on a schedule the social one ignores. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 32: The Reproductive ParadoxIn the book: Chapter 15, Women's Bodies Across the Life Course |
| Topic 33Human birth, and the first months of an infant who arrives unfinished. | A labor attended continuously, several pairs of hands afterwards, a founding microbial community from the birth canal, milk carrying sugars for the infant's bacteria, and sleep within reach of an adult. | More than one birth in five by cesarean, staff who rotate, formula without the same sugars, a mother recovering largely alone, and in many homes an infant asleep behind a closed door. | A different founding microbiome, missing feeding chemistry, more surgical births than medical need explains in some regions and too few in others, and caregiving loads that no ancestral mother carried by herself. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 33: Born Too SoonIn the book: Chapter 11, The Social Animal |
| Topic 34The developing skeleton, brain and fear response during childhood's calibration windows. | Most of the daylight hours in unsupervised, mixed-age, child-directed play, outdoors, with graded doses of real risk. | Adult-scheduled, age-segregated, refereed activity indoors, with risk engineered out and a screen in the gaps. | Bone mass unbanked before the window closes, fear left uncalibrated, and an afternoon that a phone ban empties but does not refill. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 34: The Children's MismatchIn the book: Chapter 12, Attention in the Age of the Phone |
| Topic 37Local genetic adaptation: the regional tuning of digestion, metabolism, blood and breath laid down over the last few thousand years. | The diet, altitude, sunlight and pathogens of the place where your recent ancestors lived and reproduced. | Global food supply, air travel, latitude changes within a single lifetime, and a consumer test that reports ancestry as if it reported physiology. | Mostly small mismatches (the dairy that disagrees, the flush after one glass), occasionally serious ones (sickle trait far from malaria, vitamin D deficiency far from the equator), and a steady traffic in genetic advice that outruns the evidence. | StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism. | Topic 37: The Individual VariableIn the book: Chapter 2, What Your Body Expects, and How to Trust This Book |
| Topic 39The whole set at once: immune signaling, the autonomic nervous system, metabolism, sleep and mood, linked through systemic chronic inflammation and the vagus nerve. | Inflammation as an emergency, switched on for an infection or a wound and switched off after. | A standing low-grade version of the same signal, fed by inactivity, poor diet, disrupted sleep, chronic stress, pollutants and infection. | Systems that evolved to trade with each other trade downward together, so a single-target fix often works against the rest of the wheel. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 39: The Unified Field of Mismatch |
| Topic 40Skeletal muscle, heart and lungs, the gut and the thirst reflex, all of them signal-driven. | Several hours a day of unremarkable movement, occasional hard bursts, loads carried, food that spoils, and water when thirsty. | About 5,100 steps, chairs, engines, food engineered to be eaten quickly, and a hydration industry. | Systems tuned by use drift downward in their sleep, and the drift shows up decades later as disease. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 40: The Handrail I: Move, Eat, DrinkIn the book: Chapter 1, The Short Version |
| Topic 41The circadian clock, thermoregulation, and the stress-recovery loop, all driven by environmental signals rather than conscious effort. | Thousands of lux by day, near-total darkness at night, a temperature that falls after sunset, occasional cold and heat, and daily hours outdoors. | Under 1,000 lux of waking light in the week the campers spent at home, evenings in the 30 to 300 lux band the clock reads most steeply, a thermostat that never moves, and most of a life indoors. | The clock drifts later and flattens, sleep timing scatters, and systems tuned by temperature and daylight have nothing to tune against. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 41: The Handrail II: Light, Sleep, Temperature, NatureIn the book: Chapter 1, The Short Version |
| Topic 42The social and reward circuitry that regulates contact, touch, attention and purpose. | Daily presence among a small, stable group; touch as a routine event; effort before reward; a role the group depends on. | A wide, thin network delivered through glass, touch made optional, reward decoupled from effort, and purpose left to arrange itself. | Inner-layer relationships go unfed without anyone noticing, stress physiology loses a regulator, and low purpose and low participation track higher mortality in large cohorts. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 42: The Handrail III: People, Attention, MeaningIn the book: Chapter 1, The Short Version |
| Topic 43Decision-making and habit formation, built to run on context and imitation rather than daily conscious analysis. | An environment that supplies the right behavior by default, so that eating, moving, sleeping and resting require no deliberation. | An environment that supplies none of them, plus a $6.8 trillion market selling deliberation back as the remedy. | Health becomes a permanent cognitive task; vigilance curdles into orthorexia and orthosomnia in some people, and into abandonment in many more. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 43: The Mismatch Within the MismatchIn the book: Chapter 1, The Short Version |
| Topic 45Human plasticity, the body's lifelong capacity to re-tune itself to whatever signals its surroundings supply. | A place whose ordinary defaults deliver load, daylight, darkness, heat, cold, microbes and company without anyone having to decide on them. | Environments built around cars, screens, shelf life and margin, with the missing signals sold back as effort, subscription or supplement. | Plasticity keeps working, in the direction the environment points, and health becomes a permanent act of resistance against the street you live on. | ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. | Topic 45: Designing the BridgeIn the book: Epilogue, The View from Here |
Reading the table
A book row and a reference topic that describe the same system are shown once, as the book row, with the topic linked beside it. The definition of mismatch, where the idea came from and the tests a claim has to pass are on the evolutionary mismatch page; the topic hubs gather each subject's chapters, cards and graded claims in one place.