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Reference topic 16: The Shrinking Face

Why are human jaws getting smaller? Crowded teeth explained

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.66 sources7 graded recommendationsTopic hub: Sleep and lightTopic hub: Food

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In 1985 the linguist Charles Hockett published a lecture titled simply F, crediting a hint from Carleton Coon.1 It was about f and v, the sounds you make by resting your lower lip on your upper teeth. Say "fork" and feel where your lip goes. Hunter-gatherer languages almost never used these sounds, Hockett argued. Chewing tough food wore foragers' front teeth down until, by young adulthood, they met edge to edge. Without an overbite, where the upper front teeth close over the lower, the sounds are harder to form.12

The next year the anthropologist C. Loring Brace replied with a comment titled "Egg on the face, f in the mouth, and the overbite."34 Before table knives and forks, he proposed, Europeans ate by "stuff-and-cut." They gripped food in their front teeth and sliced off a mouthful at the lips, keeping the incisors edge to edge. The modern overbite followed, in his account, when knives and forks reached ordinary tables about 250 years ago. He argued it from the history of table manners; no large dataset has since tested it.56 Bee Wilson, who popularized the idea, said Brace found the same change 900 years earlier in China, and traced it to chopsticks.6

Mismatch card

The system

The face, jaws, teeth and upper airway.

What it expects

Hard chewing from childhood, teeth that wear flat, a clear nose, little free sugar.

What it gets

Soft processed food, fork-cut mouthfuls, industrial flour and sugar, and more body weight pressing on the airway.

What happens in the gap

Jaws that fall short of their teeth (crowding, impacted wisdom teeth), retained overbites, widespread decay, and possibly, alongside weight, some sleep apnea.

The handrail

Chewable food for children, attention to snoring, a sleep study for adult warning signs, weight loss, fluoride and less sugar (●●○)

Strength of evidence

●●○ Animal, skeletal and generational studies consistently link soft diets to crowding, but genes matter too and the jaw-to-apnea link is unproven.

What this topic covers

  • ·A Face Built for Chewing
  • ·Monkeys on Soft Food
  • ·One Generation, Two Bites
  • ·The Mouth's Other Tenants
  • ·From Jaw to Airway

The practical version is in the book: Chapter 8, Sleep.

The handrail

Topics 40 to 42 hold the full program. These steps are for the mouth and airway.

Each recommendation carries the strength of the evidence behind it. How the grades work.

  1. Give children food to chew, safely

    EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested.

    Past infancy, offer age-appropriate whole foods that need chewing, not purees alone. Only animal studies and one-time snapshots of people support this. The US Centers for Disease Control and Prevention lists pieces of hard raw vegetables, nuts, tough meat, popcorn and chewing gum among choking hazards for young children. Follow pediatric guidance on texture by age.57

  2. Breastfeed if you can, without guilt if you cannot

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

    In a pooled analysis of 41 studies with 27,023 participants, ever-breastfed children had about a third the odds of malocclusion. Such comparisons cannot rule out other differences between families.58 Pediatricians recommend offering a pacifier at nap time and bedtime to reduce the risk of sudden infant death syndrome (for breastfed babies, once breastfeeding is firmly established).59 Keep it for infant sleep and ask a pediatric dentist about weaning later: pacifier use is linked to open bite and crossbite.60

  3. Take a snoring child seriously

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Pediatric guidelines call for screening all children for snoring, and a sleep study for those with other signs of apnea.61 Removing enlarged tonsils and adenoids is first-line treatment; nasal steroid sprays are an option for some mild cases.61 Warning signs include hyperactivity, bedwetting, worsening asthma and trouble paying attention.62 For mouth breathing, see Topic 10.

  4. Adults: know the three signs

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Loud snoring, observed pauses or gasping, and daytime sleepiness warrant a doctor's visit and possibly a sleep study.3862 In one 1990s study of employed adults, 82% of men and 93% of women with moderate to severe apnea had never been diagnosed.63 A physician, not an orthodontist or other dentist, makes the diagnosis.52 CPAP (continuous positive airway pressure, air pushed through a mask to hold the airway open) improves sleepiness, mood and quality of life. But a large trial in people who already had disease of the heart's or brain's arteries found that it did not prevent further cardiovascular events.64 Apnea is linked to car crashes, and CPAP use to about 72% fewer of them among drivers with apnea.65

  5. Treat excess weight

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    A 10% weight loss predicted a 26% fall in the apnea index;42 drug treatment belongs with a prescriber.

  6. Brush with fluoride and cut free sugar

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Use 1,000-1,500 ppm (parts per million) fluoride toothpaste twice a day, with your dentist's guidance on amounts for young children.3266 Keep free sugars below 10% of energy.3233

  7. Skip mewing and appliances sold as apnea prevention

    EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested.

    No preventive benefit has been shown. The orthodontists' own white paper advises widening the palate only when there is a real underlying skeletal problem, not as insurance.52

The skeptic's corner

The case against this topic, from the research itself.

Genes matter. In twin studies, estimates of heritability (the share of differences between people explained by genes) run from 35% to 81% for crowding of the lower teeth. Overbite and crossbite (upper teeth biting inside the lower) look mostly environmental. The evidence is rated low certainty.45 Among the Arara of the Amazon, one inbred village was founded by a single expelled couple. It has nearly double the malocclusion, or faulty bite, of its parent village, despite similar tooth wear.46 Kahn and colleagues call jaw change "much too fast to be evolutionary."35 That rules out new mutations, but not old genes behaving differently in a new environment.

Crooked teeth are also old. Ehrlich recalls the Stanford paleoanthropologist Richard Klein telling him, "I've never seen a hunter-gatherer skull with crooked teeth."36 Yet Qafzeh 9, a skull from Israel about 100,000 years old, has crowded teeth and a crossbite at the front.47 Naia, a teenager found by divers in a flooded Mexican cave, lived about 13,000 years ago. She had crowding, impacted lower wisdom teeth and a Class II bite, with the lower teeth set too far back. Her light tooth wear fits the chewing story; her bite does not.48 Malocclusion appears to have been rarer before farming, not absent. The farming signal in skulls is real but "relatively small," with neutral processes such as random drift and migration doing most of the shaping.49 The f story is contested too. A preprint, not yet peer reviewed, traced it to distance from Africa, not diet; Blasi's team replied in another that the reanalysis used ill-specified models.5051

The airway claims are shakier still. The American Association of Orthodontists finds "no indication in the literature" that widening a child's palate as a precaution prevents later apnea.52 One review said interest in nasal obstruction and facial growth was fueled by "strong convictions, weak evidence."53 Mewing, pressing the tongue flat against the roof of the mouth to reshape the jaw, is named for the British orthodontist John Mew. A dentist-reviewed WebMD guide finds "no serious research" suggesting it can reshape the jawline.54 In November 2024 a UK General Dental Council committee struck Michael Mew, who practices orthotropics (a method meant to guide facial growth), off the dental register. Treatment he recommended for two six-year-olds, it found, was not clinically indicated. The High Court dismissed his appeal in May 2026.5556

Nobody has run the trial that would settle it: chewier diets in young children, or childhood food texture followed into an adult sleep laboratory.

Terms this topic defines

Related topics

Sources cited above

  1. 1.Hockett, C.F. (1985). "Distinguished Lecture: F." American Anthropologist, 87(2), 263-281. https://doi.org/10.1525/aa.1985.87.2.02a00020 (Hockett's argument as summarized in note 2.) (Hockett credited Carleton Coon, who "15 years ago gave me the hint that has led to this paper")
  2. 2.Bower, B. (2019, 14 March). "The rise of farming changed how people talk." Science News. https://www.sciencenews.org/article/rise-farming-altered-our-bite-and-changed-how-people-talk (Blasi's team studied more than 2,400 populations; hunter-gatherers used on average about one labiodental sound for every four in food-producing societies)
  3. 3.Smith, S.L., and Hunt, K.D. (2020). "Charles Loring Brace, IV (1930-2019)." American Journal of Physical Anthropology, 171(4), 567-568. https://doi.org/10.1002/ajpa.24018
  4. 4.Brace, C.L. (1986). "Egg on the face, f in the mouth, and the overbite." American Anthropologist, 88(3), 695-697. https://doi.org/10.1525/aa.1986.88.3.02a00150
  5. 5.Brace, C.L. (1977). "Occlusion to the anthropological eye." In J.A. McNamara (ed.), The Biology of Occlusal Development, Monograph 7, Craniofacial Growth Series. Center for Human Growth and Development, University of Michigan, pp. 179-209 (citation confirmed through citing sources; the chapter itself was not seen). An interpretive hypothesis rather than a large tested dataset; the account given here follows its popular telling in Wilson (2012), note 6.
  6. 6.Flatow, I. (host), and Wilson, B. (2012, 28 December). "'Consider the Fork' Chronicles Evolution of Eating." Science Friday, NPR (transcript). https://www.npr.org/transcripts/168203187. See also Wilson, B. (2012). Consider the Fork: A History of How We Cook and Eat. Basic Books. (Wilson called "the real clincher" the fact that Brace "found this change 900 years earlier in China, the reason being chopsticks")
  7. 7.Blasi, D.E., Moran, S., Moisik, S.R., Widmer, P., et al. (2019). "Human sound systems are shaped by post-Neolithic changes in bite configuration." Science, 363(6432), eaav3218. https://doi.org/10.1126/science.aav3218
  8. 45.Santana, L.G., Flores-Mir, C., Iglesias-Linares, A., Pithon, M.M., et al. (2020). "Influence of heritability on occlusal traits: a systematic review of studies in twins." Progress in Orthodontics, 21(1), 29. https://doi.org/10.1186/s40510-020-00330-8
  9. 46.Normando, D., Faber, J., Guerreiro, J.F., and Quintão, C.C.A. (2011). "Dental occlusion in a split Amazon indigenous population: genetics prevails over environment." PLoS ONE, 6(12), e28387. https://doi.org/10.1371/journal.pone.0028387
  10. 35.Kahn, S., Ehrlich, P., Feldman, M., Sapolsky, R., et al. (2020). "The jaw epidemic: recognition, origins, cures, and prevention." BioScience, 70(9), 759-771. https://doi.org/10.1093/biosci/biaa073 (the authors also blamed how people now hold their jaws at rest and in sleep)
  11. 36.Kubota, T. (2018, 16 April). "The epidemic of undersized jaws according to Paul Ehrlich." Stanford Medicine News Center, Insights. https://med.stanford.edu/news/insights/2018/04/the-epidemic-of-undersized-jaws-according-to-paul-ehrlich.html
  12. 47.Sarig, R., Slon, V., Abbas, J., May, H., et al. (2013). "Malocclusion in early anatomically modern human: a reflection on the etiology of modern dental misalignment." PLoS ONE, 8(11), e80771. https://doi.org/10.1371/journal.pone.0080771 (5.8 mm of crowding and an anterior crossbite)
  13. 48.Herrera-Atoche, J.R., Chatters, J.C., and Cucina, A. (2022). "Unexpected malocclusion in a 13,000-Year-old Late Pleistocene young woman from Mexico." Scientific Reports, 12(1), 3997. https://doi.org/10.1038/s41598-022-07941-7
  14. 49.Katz, D.C., Grote, M.N., and Weaver, T.D. (2017). "Changes in human skull morphology across the agricultural transition are consistent with softer diets in preindustrial farming groups." PNAS, 114(34), 9050-9055. https://doi.org/10.1073/pnas.1702586114
  15. 50.Tarasov, S., and Uyeda, J.C. (2020). "Causal modeling refutes Hockett's hypothesis that bite configuration affects human sound evolution." bioRxiv (preprint, not peer reviewed as seen). https://doi.org/10.1101/2020.02.20.957407 (posted in 2020)
  16. 51.Blasi, D.E., Moran, S., Moisik, S., Widmer, P., et al. (2020). "Languages, evolution and statistics: human sound systems were shaped by changes in bite configuration. Response to Tarasov & Uyeda (2020)." bioRxiv (preprint, not peer reviewed as seen). https://doi.org/10.1101/2020.02.27.965400
  17. 52.Behrents, R.G., Shelgikar, A.V., Conley, R.S., Flores-Mir, C., et al. (2019). "Obstructive sleep apnea and orthodontics: An American Association of Orthodontists White Paper." American Journal of Orthodontics and Dentofacial Orthopedics, 156(1), 13-28.e1. https://doi.org/10.1016/j.ajodo.2019.04.009 (amended PDF, 15 March 2019: https://www2.aaoinfo.org/wp-content/uploads/2019/03/sleep-apnea-white-paper-amended-March-2019.pdf)
  18. 53.Vig, K.W. (1998). "Nasal obstruction and facial growth: the strength of evidence for clinical assumptions." American Journal of Orthodontics and Dentofacial Orthopedics, 113(6), 603-611. https://doi.org/10.1016/s0889-5406(98)70219-7
  19. 54.Frysh, P., and King, L.M. (2026). "What Is Mewing?" WebMD (medically reviewed by R. Brennan, 26 June 2026). https://www.webmd.com/oral-health/what-is-mewing
  20. 55.General Dental Council (2026). Online Register, entry for Michael Gordon Mew, registration number 69138 (accessed 19 September 2026). https://olr.gdc-uk.org/SearchRegister/SearchResult?RegistrationNumber=69138
  21. 56.Peakin, W. (2024, 12 November). "Dentist struck off for inappropriate and misleading treatment." Scottish Dental magazine. https://www.sdmag.co.uk/2024/11/12/inappropriate-and-misleading-treatment/
  22. 57.Centers for Disease Control and Prevention (n.d.). Choking Hazards. https://www.cdc.gov/infant-toddler-nutrition/foods-and-drinks/choking-hazards.html
  23. 58.Peres, K.G., Cascaes, A.M., Nascimento, G.G., and Victora, C.G. (2015). "Effect of breastfeeding on malocclusions: a systematic review and meta-analysis." Acta Paediatrica, 104(S467), 54-61. https://doi.org/10.1111/apa.13103
  24. 59.Moon, R.Y., Carlin, R.F., and Hand, I. (2022). "Sleep-related infant deaths: updated 2022 recommendations for reducing infant deaths in the sleep environment." Pediatrics, 150(1), e2022057990. https://doi.org/10.1542/peds.2022-057990
  25. 60.Schmid, K.M., Kugler, R., Nalabothu, P., Bosch, C., et al. (2018). "The effect of pacifier sucking on orofacial structures: a systematic literature review." Progress in Orthodontics, 19(1), 8. https://doi.org/10.1186/s40510-018-0206-4
  26. 61.Marcus, C.L., Brooks, L.J., Draper, K.A., Gozal, D., et al. (2012). "Diagnosis and management of childhood obstructive sleep apnea syndrome." Pediatrics, 130(3), 576-584. https://doi.org/10.1542/peds.2012-1671
  27. 62.National Heart, Lung, and Blood Institute (2025). Sleep Apnea: Symptoms (last updated 9 January 2025). https://www.nhlbi.nih.gov/health/sleep-apnea/symptoms
  28. 38.Punjabi, N.M. (2008). "The epidemiology of adult obstructive sleep apnea." Proceedings of the American Thoracic Society, 5(2), 136-143. https://doi.org/10.1513/pats.200709-155MG
  29. 63.Young, T., Evans, L., Finn, L., and Palta, M. (1997). "Estimation of the clinically diagnosed proportion of sleep apnea syndrome in middle-aged men and women." Sleep, 20(9), 705-706. https://doi.org/10.1093/sleep/20.9.705
  30. 64.McEvoy, R.D., Antic, N.A., Heeley, E., Luo, Y., et al. (2016). "CPAP for prevention of cardiovascular events in obstructive sleep apnea." New England Journal of Medicine, 375(10), 919-931. https://doi.org/10.1056/NEJMoa1606599
  31. 65.Tregear, S., Reston, J., Schoelles, K., and Phillips, B. (2010). "Continuous positive airway pressure reduces risk of motor vehicle crash among drivers with obstructive sleep apnea: systematic review and meta-analysis." Sleep, 33(10), 1373-1380. https://doi.org/10.1093/sleep/33.10.1373
  32. 42.Peppard, P.E., Young, T., Palta, M., Dempsey, J., et al. (2000). "Longitudinal study of moderate weight change and sleep-disordered breathing." JAMA, 284(23), 3015-3021. https://doi.org/10.1001/jama.284.23.3015 (690 adults in the Wisconsin cohort)
  33. 32.World Health Organization (2025). Oral health (fact sheet, 17 March 2025). https://www.who.int/news-room/fact-sheets/detail/oral-health (untreated decay in permanent teeth is the world's most common health condition according to the Global Burden of Disease 2021)
  34. 66.Walsh, T., Worthington, H.V., Glenny, A.M., Marinho, V.C.C., et al. (2019). "Fluoride toothpastes of different concentrations for preventing dental caries." Cochrane Database of Systematic Reviews, 3, CD007868. https://doi.org/10.1002/14651858.CD007868.pub3
  35. 33.Moynihan, P.J., and Kelly, S.A.M. (2014). "Effect on caries of restricting sugars intake: systematic review to inform WHO guidelines." Journal of Dental Research, 93(1), 8-18. https://doi.org/10.1177/0022034513508954 (42 of 50 studies in children linked sugar to caries)

This topic carries 66 notes in the research manuscript; the 35 above are those behind the material on this page. Full source register.