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Chapter 2 of the book

What Your Body Expects, and How to Trust This Book

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.3 things to start with9 popular claims graded58 works cited

How the chapter opens

In 1911 Ethel Margaret Burnside, Hertfordshire's first "chief health visitor and lady inspector of midwives," set up "an army of trained nurses" and got the county to buy spring balances, so that every baby could be weighed at birth and again at one year. "The cyclometer on my bicycle registered 2921 miles this year," she wrote. The nurses' records were copied into ledgers "in immaculate handwriting, a separate ledger for each village."

Decades later, David Barker's team in Southampton compared areas of England and Wales and found that death rates from heart disease tracked the rates at which babies had died about half a century earlier. "It is suggested," they wrote, "that poor nutrition in early life increases susceptibility to the effects of an affluent diet."1 Maps cannot show individuals. To test the idea, Barker needed babies weighed early in the century who could be traced as adults, and Burnside had left him exactly that.

What the chapter covers

The argument, the studies and the stories are in the book. Get the book.

  • ·Three Clocks
  • ·Too Little, Too Much, Too New
  • ·You Are Not Average
  • ·How to Trust This Book
  • ·Nine Claims, Graded
  • ·What Survives the Critique

Mismatch card

The system

The whole body, read on three clocks: genes over generations, development over a lifetime, physiology over days and weeks.

What it expects

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.

What it gets

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).

What happens in the gap

Many chronic diseases are suspected mismatches, graded chapter by chapter; local genetic tuning means the gap differs from person to person.

The handrail

Restore missing signals on the fastest clock, physiology, and judge every claim by the study behind it. (ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.)

Strength of evidence

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. The measured gaps between past and present are well documented; evolutionary explanations for particular diseases are mostly hypotheses, and the doses come from trials.

Nine claims, graded

The table this chapter uses to show how the book judges a claim.

The protocol

Each action carries the book's evidence grade. How the grades work.

This protocol is short. Most of the book applies to everyone; these are the places where your own inheritance changes what you should do, plus one habit that owes nothing to evolution and is here on purpose. Evolution tells you what your body expects. Trials tell you how much. The habit is how you check the trials.

Start here

  1. Settle the dairy question with a two-week trial, not a DNA kit

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    How: if milk reliably brings bloating, gas or cramps, switch to lactose-free dairy, or take a lactase enzyme with dairy, for two weeks. Then drink ordinary milk again on purpose and see what happens. Fermented dairy such as yogurt is often fine when milk is not. Why: losing lactase after childhood is the normal state for most adults on earth. Persistent gut symptoms still deserve a doctor, since celiac disease and inflammatory bowel disease can imitate lactose trouble.

  2. Check one thing you already pay for (a habit, not a treatment)

    How: pick the supplement, powder or program you spend the most on. Find the study it rests on and ask the five questions above. If you cannot find a study, or it measured something else, stop buying it for a month. Why: the claims in the table above failed exactly this check.

  3. If a drink turns your face red, whatever your background, treat it as a stop sign

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    How: drink less, or not at all; the less you drink, the lower the risk. Do not hide the flush with antihistamines, antacids or products sold for the purpose, since that removes the warning and leaves the acetaldehyde. Why: the flush marks a slow-clearing enzyme and, with continued drinking, a substantially higher risk of cancer of the esophagus.

Then, pick from this menu

  • **Match vitamin D to your skin and latitude (ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.).** How: the vitamin D your skin makes from sun depends on its pigment and on your distance from the equator. If you have darker skin and live far from the equator, Chapter 7 covers who might need a supplement or a test.

  • **Let your plate follow your culture (ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.).** How: build meals from many whole foods rather than one refined staple, in whatever tradition you eat; Chapter 5 gives the pattern and the amounts. Why: diets as different as the Turkana's and the Tsimane's both went with low heart risk.

  • **Skip the ancestry kit as a guide to health (ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.).** A haplogroup never reads the genes that matter, and a risk score shifts odds without diagnosing.

If this is you

East Asian family background

the flush variant is common. If you flush, the stop-sign rule applies at any dose, and masking the flush with a pill does not lower the risk.

Family roots where adult milk-drinking was rare

expect dairy trouble; the two-week trial settles it cheaply.

Over 50, or perimenopause and after

if dairy bothers you, swap rather than cut. Lactose-free milk, yogurt and cheese keep an easy source of protein in your meals as you age, when expert groups advise eating more of it (Chapter 4).

Heading to the mountains (skiing, trekking, a high-altitude city)

go up gradually, build in rest days, learn the signs of altitude sickness, and go down if they get worse. The adaptations of Tibetans and Andeans shift population averages and exempt no individual.

Holding a genetic result, from a clinic or a kit

take it to a clinician before acting on it, and never stop a medicine because of it.

Tight budget

the two most useful tests in this chapter cost little or nothing. Notice whether you flush, and for the dairy trial simply leave milk out for two weeks if lactose-free products are too dear.

Short on time

most people already know whether they flush; if you are unsure, notice next time rather than testing on purpose. The dairy trial means swapping one product in your fridge for two weeks.

Safety

Altitude illness includes fluid on the lungs or brain, and either can kill; if symptoms worsen, go down. Never stop a prescribed medicine because of a genetic result or a dairy trial.

The skeptic's box

What could overturn this chapter, from the chapter itself.

Evolutionary explanations are easy to invent and hard to test. The founders of the mismatch idea said early on that their evidence "could only suggest testable hypotheses," and their claim that "our genes have hardly changed" collides with a genomic analysis concluding that human selection had "accelerated greatly during the last 40,000 years."27 Knowing the story is not a cure, either. In one small randomized trial, adults given a web program framed around mismatch changed their activity and eating only slightly more than a control group, and the differences "did not reach significance."28 That is why this book uses evolution only to decide where to look, and takes its doses from trials.

What would weaken the frame? Gene variants that should help in traditional settings and harm in modern ones, sought in peoples now moving to towns, and not found. What would sink it? Trials in which restoring a missing signal, such as movement, daylight or company, did nothing. The chapters that follow report those trials, including the ones that found less than the enthusiasts claim.

Go deeper in the reference library

The research this chapter was built from, as longer reference entries: each with its own mismatch card, graded recommendations and the case against it.

See also in the book

Sources behind this page

  1. 1.Barker, D.J., and Osmond, C. (1986). "Infant mortality, childhood nutrition, and ischaemic heart disease in England and Wales." The Lancet, 327(8489), 1077-1081. https://doi.org/10.1016/s0140-6736(86)91340-1 (212 areas; heart disease deaths in 1968-78 set against infant deaths in 1921-25)
  2. 27.Konner, M., and Eaton, S.B. (2010). "Paleolithic nutrition: twenty-five years later." Nutrition in Clinical Practice, 25(6), 594-602. https://doi.org/10.1177/0884533610385702 ; Eaton, S.B., Konner, M., and Shostak, M. (1988). "Stone agers in the fast lane: chronic degenerative diseases in evolutionary perspective." American Journal of Medicine, 84(4), 739-749. https://doi.org/10.1016/0002-9343(88)90113-1 ; Hawks, J., Wang, E.T., Cochran, G.M., Harpending, H.C., et al. (2007). "Recent acceleration of human adaptive evolution." PNAS, 104(52), 20753-20758. https://doi.org/10.1073/pnas.0707650104
  3. 28.Grey, E.B., Thompson, D., and Gillison, F.B. (2019). "Effects of a web-based, evolutionary mismatch-framed intervention targeting physical activity and diet: a randomised controlled trial." International Journal of Behavioral Medicine, 26(6), 645-657. https://doi.org/10.1007/s12529-019-09821-3 (correction 2023: https://doi.org/10.1007/s12529-023-10169-y) (60 overweight or obese adults; 12-week program)
  4. 18.Johnson, G.H., and Fritsche, K. (2012). "Effect of dietary linoleic acid on markers of inflammation in healthy persons: a systematic review of randomized controlled trials." Journal of the Academy of Nutrition and Dietetics, 112(7), 1029-1041. https://doi.org/10.1016/j.jand.2012.03.029 (15 randomized controlled trials)
  5. 19.Costard, S., Espejo, L., Groenendaal, H., and Zagmutt, F.J. (2017). "Outbreak-related disease burden associated with consumption of unpasteurized cow's milk and cheese, United States, 2009-2014." Emerging Infectious Diseases, 23(6), 957-964. https://doi.org/10.3201/eid2306.151603 (raw milk is consumed by 3.2% and unpasteurized cheese by 1.6% of the US population)
  6. 20.Chevalier, G., Sinatra, S.T., Oschman, J.L., Sokal, K., et al. (2012). "Earthing: health implications of reconnecting the human body to the earth's surface electrons." Journal of Environmental and Public Health, 2012, 291541. https://doi.org/10.1155/2012/291541 ; Oschman, J.L., Chevalier, G., and Brown, R. (2015). "The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases." Journal of Inflammation Research, 8, 83-96. https://doi.org/10.2147/JIR.S69656 (narrative reviews by authors who advocate the practice)
  7. 21.Lennerz, B.S., Mey, J.T., Henn, O.H., and Ludwig, D.S. (2021). "Behavioral characteristics and self-reported health status among 2029 adults consuming a 'carnivore diet'." Current Developments in Nutrition, 5(12), nzab133. https://doi.org/10.1093/cdn/nzab133 (95% reported better overall health; median LDL cholesterol was 172 mg/dL)
  8. 22.Rhee, J., Iansavitchene, A., Mannala, S., Graham, M.E., et al. (2025). "Breaking social media fads and uncovering the safety and efficacy of mouth taping in patients with mouth breathing, sleep disordered breathing, or obstructive sleep apnea: a systematic review." PLOS ONE, 20(5), e0323643. https://doi.org/10.1371/journal.pone.0323643
  9. 23.Ridge, S.T., Olsen, M.T., Bruening, D.A., and Jurgensmeier, K. (2019). "Walking in minimalist shoes is effective for strengthening foot muscles." Medicine and Science in Sports and Exercise, 51(1), 104-113. https://doi.org/10.1249/MSS.0000000000001751 (eight weeks, runners) ; Curtis, R., Willems, C., Paoletti, P., and D'Août, K. (2021). "Daily activity in minimal footwear increases foot strength." Scientific Reports, 11, 18648. https://doi.org/10.1038/s41598-021-98070-0 (six months; foot strength rose 57.4%)
  10. 24.Søberg, S., et al. (2021). Cell Reports Medicine, 2, 100408 (Scandinavian winter swimmers combining cold water and sauna, 8 against 8 controls; do not read as more brown fat)
  11. 25.Green, A.C., Williams, G.M., Logan, V., and Strutton, G.M. (2011). "Reduced melanoma after regular sunscreen use: randomized trial follow-up." Journal of Clinical Oncology, 29(3), 257-263. https://doi.org/10.1200/JCO.2010.28.7078 (the Nambour trial: 1,621 adults randomized in 1992-96 and followed to 2006; hazard ratio for invasive melanoma 0.27, 95% CI 0.08-0.97)

Every work this chapter cites

The chapter's 28 notes cite 58 works, listed by note number. Each is also in the full source register.

  1. 1.Barker, D.J., and Osmond, C (1986). Infant mortality, childhood nutrition, and ischaemic heart disease in England and Wales. The Lancet. 10.1016/s0140-6736(86
  2. 2.Barker, D (2003). The midwife, the coincidence, and the hypothesis. BMJ. 10.1136/bmj.327.7429.1428
  3. 3.Barker, D.J., Winter, P.D., Osmond, C., Margetts, B., et al (1989). Weight in infancy and death from ischaemic heart disease. The Lancet. 10.1016/s0140-6736(89Huxley, R., Owen, C.G., Whincup, P.H., Cook, D.G., et al (2007). Is birth weight a risk factor for ischemic heart disease in later life? American Journal of Clinical Nutrition. 10.1093/ajcn/85.5.1244
  4. 4.Griffiths, P.E., and Bourrat, P (2023). Integrating evolutionary, developmental and physiological mismatch. Evolution, Medicine, and Public Health. 10.1093/emph/eoad023Hales, C.N., and Barker, D.J (1992). Type 2 (non-insulin-dependent) diabetes mellitus: the thrifty phenotype hypothesis. Diabetologia. 10.1007/BF00400248Hales, C.N., and Barker, D.J (2001). The thrifty phenotype hypothesis. British Medical Bulletin. 10.1093/bmb/60.1.5
  5. 5.Nagy, K.A (2005). Field metabolic rate and body size. Journal of Experimental Biology. 10.1242/jeb.01553Gerkema, M.P., Davies, W.I., Foster, R.G., Menaker, M., et al (2013). The nocturnal bottleneck and the evolution of activity patterns in mammals. Proceedings of the Royal Society B. 10.1098/rspb.2013.0508
  6. 6.Sockol, M.D., Raichlen, D.A., and Pontzer, H (2007). Chimpanzee locomotor energetics and the origin of human bipedalism. PNAS. 10.1073/pnas.0703267104Kamberov, Y.G., Guhan, S.M., DeMarchis, A., Jiang, J., et al (2018). Comparative evidence for the independent evolution of hair and sweat gland traits in primates. Journal of Human Evolution. 10.1016/j.jhevol.2018.10.008Liebenberg, L (2006). Persistence hunting by modern hunter-gatherers. Current Anthropology. 10.1086/508695Pickering, T.R., and Bunn, H.T (2007). The endurance running hypothesis and hunting and scavenging in savanna-woodlands. Journal of Human Evolution. 10.1016/j.jhevol.2007.01.012
  7. 7.Raichle, M.E., and Gusnard, D.A (2002). Appraising the brain's energy budget. PNAS. 10.1073/pnas.172399499Aiello, L.C (1997). Brains and guts in human evolution: the expensive tissue hypothesis. Brazilian Journal of Genetics. 10.1590/S0100-84551997000100023Pontzer, H., Brown, M.H., Raichlen, D.A., Dunsworth, H., et al (2016). Metabolic acceleration and the evolution of human brain size and life history. Nature. 10.1038/nature17654Carmody, R.N., and Wrangham, R.W (2009). The energetic significance of cooking. Journal of Human Evolution. 10.1016/j.jhevol.2009.02.011
  8. 8.Larson, G., Piperno, D.R., Allaby, R.G., Purugganan, M.D., et al (2014). Current perspectives and the future of domestication studies. PNAS. 10.1073/pnas.1323964111Cohen, M.N., and Armelagos, G.J., eds (1984). Paleopathology at the Origins of Agriculture. Mummert, A., Esche, E., Robinson, J., and Armelagos, G.J (2011). Stature and robusticity during the agricultural transition: evidence from the bioarchaeological record. Economics & Human Biology. 10.1016/j.ehb.2011.03.004Larsen, C.S (1995). Biological changes in human populations with agriculture. Annual Review of Anthropology. 10.1146/annurev.an.24.100195.001153Bocquet-Appel, J.-P (2011). When the world's population took off: the springboard of the Neolithic Demographic Transition. Science. 10.1126/science.1208880Wang, K., Prüfer, K., Krause-Kyora, B., Childebayeva, A., et al (2023). High-coverage genome of the Tyrolean Iceman reveals unusually high Anatolian farmer ancestry. Cell Genomics. 10.1016/j.xgen.2023.100377South Tyrol Museum of Archaeology The body. iceman.itKeller, A., Graefen, A., Ball, M., Matzas, M., et al (2012). New insights into the Tyrolean Iceman's origin and phenotype as inferred by whole-genome sequencing. Nature Communications. 10.1038/ncomms1701Maixner, F., Turaev, D., Cazenave-Gassiot, A., Janko, M., et al (2018). The Iceman's last meal consisted of fat, wild meat, and cereals. Current Biology. 10.1016/j.cub.2018.05.067
  9. 9.Gurven, M.D., and Lieberman, D.E (2020). WEIRD bodies: mismatch, medicine and missing diversity. Evolution and Human Behavior. 10.1016/j.evolhumbehav.2020.04.001
  10. 10.Lea, A.J., Clark, A.G., Dahl, A.W., Devinsky, O., et al (2023). Applying an evolutionary mismatch framework to understand disease susceptibility. PLOS Biology. 10.1371/journal.pbio.3002311
  11. 11.Lea, A.J., Martins, D., Kamau, J., Gurven, M., et al (2020). Urbanization and market integration have strong, nonlinear effects on cardiometabolic health in the Turkana. Science Advances. 10.1126/sciadv.abb1430Cipriani, A., Furukawa, T.A., Salanti, G., Chaimani, A., et al (2018). Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. The Lancet. 10.1016/S0140-6736(17
  12. 12.Enattah, N.S., Sahi, T., Savilahti, E., Terwilliger, J.D., Peltonen, L., and Järvelä, I (2002). Identification of a variant associated with adult-type hypolactasia. Nature Genetics. 10.1038/ng826Tishkoff, S.A., Reed, F.A., Ranciaro, A., Voight, B.F., et al (2007). Convergent adaptation of human lactase persistence in Africa and Europe. Nature Genetics. 10.1038/ng1946Evershed, R.P., Davey Smith, G., Roffet-Salque, M., Timpson, A., et al (2022). Dairying, diseases and the evolution of lactase persistence in Europe. Nature. 10.1038/s41586-022-05010-7
  13. 13.Brooks, P.J., Enoch, M.A., Goldman, D., Li, T.K., and Yokoyama, A (2009). The alcohol flushing response: an unrecognized risk factor for esophageal cancer from alcohol consumption. PLoS Medicine. 10.1371/journal.pmed.1000050
  14. 14.Huerta-Sánchez, E., Jin, X., Asan, Bianba, Z., et al (2014). Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA. Nature. 10.1038/nature13408Beall, C.M., Cavalleri, G.L., Deng, L., Elston, R.C., et al (2010). Natural selection on EPAS1 (HIF2alpha) associated with low hemoglobin concentration in Tibetan highlanders. Proceedings of the National Academy of Sciences. 10.1073/pnas.1002443107Beall, C.M (2007). Two routes to functional adaptation: Tibetan and Andean high-altitude natives. Proceedings of the National Academy of Sciences. 10.1073/pnas.0701985104Alkorta-Aranburu, G., Beall, C.M., Witonsky, D.B., Gebremedhin, A., Pritchard, J.K., and Di Rienzo, A (2012). The genetic architecture of adaptations to high altitude in Ethiopia. PLoS Genetics. 10.1371/journal.pgen.1003110
  15. 15.Trumble, B.C., Stieglitz, J., Blackwell, A.D., Allayee, H., et al (2017). Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden. The FASEB Journal. 10.1096/fj.201601084R
  16. 16.Bang, H.O., Dyerberg, J., and Nielsen, A.B (1971). Plasma lipid and lipoprotein pattern in Greenlandic West-coast Eskimos. The Lancet. 10.1016/S0140-6736(71Fodor, J.G., Helis, E., Yazdekhasti, N., and Vohnout, B (2014). 'Fishing' for the origins of the 'Eskimos and heart disease' story: facts or wishful thinking? Canadian Journal of Cardiology. 10.1016/j.cjca.2014.04.007
  17. 17.Zuk, M (2013). Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live. Basner, M., Babisch, W., Davis, A., Brink, M., et al (2014). Auditory and non-auditory effects of noise on health. The Lancet. 10.1016/S0140-6736(13
  18. 18.Johnson, G.H., and Fritsche, K (2012). Effect of dietary linoleic acid on markers of inflammation in healthy persons: a systematic review of randomized controlled trials. Journal of the Academy of Nutrition and Dietetics. 10.1016/j.jand.2012.03.029
  19. 19.Costard, S., Espejo, L., Groenendaal, H., and Zagmutt, F.J (2017). Outbreak-related disease burden associated with consumption of unpasteurized cow's milk and cheese, United States, 2009-2014. Emerging Infectious Diseases. 10.3201/eid2306.151603
  20. 20.Chevalier, G., Sinatra, S.T., Oschman, J.L., Sokal, K., and Sokal, P (2012). Earthing: health implications of reconnecting the human body to the earth's surface electrons. Journal of Environmental and Public Health. 10.1155/2012/291541Oschman, J.L., Chevalier, G., and Brown, R (2015). The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases. Journal of Inflammation Research. 10.2147/JIR.S69656
  21. 21.Lennerz, B.S., Mey, J.T., Henn, O.H., and Ludwig, D.S (2021). Behavioral characteristics and self-reported health status among 2029 adults consuming a 'carnivore diet'. Current Developments in Nutrition. 10.1093/cdn/nzab133
  22. 22.Rhee, J., Iansavitchene, A., Mannala, S., Graham, M.E., et al (2025). Breaking social media fads and uncovering the safety and efficacy of mouth taping in patients with mouth breathing, sleep disordered breathing, or obstructive sleep apnea: a systematic review. PLOS ONE. 10.1371/journal.pone.0323643
  23. 23.Ridge, S.T., Olsen, M.T., Bruening, D.A., Jurgensmeier, K., et al (2019). Walking in minimalist shoes is effective for strengthening foot muscles. Medicine and Science in Sports and Exercise. 10.1249/MSS.0000000000001751Curtis, R., Willems, C., Paoletti, P., and D'Août, K (2021). Daily activity in minimal footwear increases foot strength. Scientific Reports. 10.1038/s41598-021-98070-0
  24. 24.Søberg, S., et al (2021). Cell Reports Medicine.
  25. 25.Green, A.C., Williams, G.M., Logan, V., and Strutton, G.M (2011). Reduced melanoma after regular sunscreen use: randomized trial follow-up. Journal of Clinical Oncology. 10.1200/JCO.2010.28.7078
  26. 26.Gurven, M., and Kaplan, H (2007). Longevity among hunter-gatherers: a cross-cultural examination. Population and Development Review. 10.1111/j.1728-4457.2007.00171.x
  27. 27.Konner, M., and Eaton, S.B (2010). Paleolithic nutrition: twenty-five years later. Nutrition in Clinical Practice. 10.1177/0884533610385702Eaton, S.B., Konner, M., and Shostak, M (1988). Stone agers in the fast lane: chronic degenerative diseases in evolutionary perspective. American Journal of Medicine. 10.1016/0002-9343(88Hawks, J., Wang, E.T., Cochran, G.M., Harpending, H.C., et al (2007). Recent acceleration of human adaptive evolution. PNAS. 10.1073/pnas.0707650104
  28. 28.Grey, E.B., Thompson, D., and Gillison, F.B (2019). Effects of a web-based, evolutionary mismatch-framed intervention targeting physical activity and diet: a randomised controlled trial. International Journal of Behavioral Medicine. 10.1007/s12529-019-09821-3

The full source register

This page carries the chapter's apparatus. The chapter itself, and the fifteen others, are in the book.

Get the bookThe 30-day protocolAll sixteen chapters