Wisdom Teeth and the Modern Jaw

"It appears as if the posterior molar or wisdom-teeth were tending to become rudimentary in the more civilised races of man." — Charles Darwin, The Descent of Man, 1871¹

"Our fossil forebears did not have impacted wisdom teeth, and few appear to have had gum disease." — Peter Ungar, Scientific American, 2020²

Summary

The parent article, Vestigial Structures, separates two claims: that an organ is useless, and that it is a reduced copy of something larger in an ancestor. The third molar is the one human case where a third claim is added, that the jaw shrank faster than the teeth and left the last molar with nowhere to go. This article tests all three against the measured record.

The claim has not changed since 1871, and Darwin gave the diet explanation himself. Darwin wrote that wisdom teeth "were tending to become rudimentary in the more civilised races of man," and that the shortened back of the jaw "may, I presume, be safely attributed to civilised men habitually feeding on soft, cooked food, and thus using their jaws less."¹ Wiedersheim in 1895 traced molar cusp reduction to "Man's adoption of a more delicate diet."³ Scientific American in 2016 still listed wisdom teeth among "useless vestigial structures."⁴
Two numbers, two different histories. Worldwide, 22.63 percent of people never form at least one third molar, and 24.40 percent have at least one impacted.⁵⁶ Agenesis is heritable and "dates back to at least early Homo erectus."⁷ Impaction is recent: in the archaeological samples Katherine Carter measured it "remained at such low frequencies during the agricultural transition" that selection against it "is unlikely to have been a causative force,"⁷ at 3.4 percent of farming-era skeletons against 15.0 percent of industrial-era ones.⁷
The jaw shrinks in one lifetime; the teeth do not. Hunter-gatherers have "consistently longer and narrower mandibles than agriculturalists,"⁸ the mismatch "began to arise with the shift towards sedentism and agricultural subsistence practices several millennia ago,"⁹ and rats, squirrel monkeys, baboons and hyraxes raised on soft food grow narrower arches and about 10 percent less lower face.¹⁰¹¹ The effect is real and modest: in the largest skull dataset the diet signal is "relatively small."¹²
On the mainstream fossil series, the tooth itself shrank. "In all fossil hominins the second or third molar is the largest tooth on average"; in modern humans the first is, "producing disproportionately decreased third molars."¹³¹³ Tooth size fell "1% every 2,000 years" through the last glaciation and "approximately 1% per thousand years" since.¹⁴¹⁴ This is the reduction claim proper, and it stands or falls with the tree.
Weston Price saw the pattern and guessed the mechanism. Among isolated northern Indians he found "practically no irregular teeth, including no impacted third molars,"¹⁵ and crooked teeth "in the new generation" after the switch to trade foods.¹⁵ He inferred "intercepted heredity" from the parents' nutrition.¹⁵ He measured no jaws; the later experiments point to chewing load, not vitamins.
A tooth that half fits has a real cost, and most of the cost is optional. Distal caries in the second molar drives "up to 5%" of lower third-molar removals.¹⁶ In 2000 NICE ruled that prophylactic removal "should be discontinued in the NHS,"¹⁷ and the 2020 Cochrane review found "insufficient evidence" either way.¹⁸ A third of teeth impacted at 18 have erupted by 26.¹⁹
The creationist literature is right about diet and function, and answers the wrong claim on ancestry. Bergman in 1998 named diet "probably" the most important factor,²⁰ which the mainstream work above confirms. But "they aid in chewing" answers the 1893 useless-organ claim, and his objection that no one can "identify what advantage a smaller jaw would have"²⁰ misses that the mainstream model needs no advantage: relaxed selection plus mutation, which is what Bergman himself calls "devolution."

Verdict: the third molar passes the reduction test on either side's reading. Diet explains the modern impaction epidemic and removes the bad-design charge; it does not explain agenesis or the fossil size trend, so the ancestral reading survives as a claim about the tree, which is the parent article's step 3 and not a fact about teeth.

Part 1: The claim, from Darwin to Scientific American

Darwin made the claim in the first chapter of The Descent of Man (1871), in a list of human rudiments. "It appears as if the posterior molar or wisdom-teeth were tending to become rudimentary in the more civilised races of man. These teeth are rather smaller than the other molars, as is likewise the case with the corresponding teeth in the chimpanzee and orang; and they have only two separate fangs. They do not cut through the gums till about the seventeenth year, and I am assured by dentists that they are much more liable to decay, and are earlier lost, than the other teeth. It is also remarkable that they are much more liable to vary both in structure and in the period of their development than the other teeth."¹ "In the Melanian races, on the other hand, the wisdom-teeth are usually furnished with three separate fangs, and are generally sound."¹

Then comes the sentence the creationist literature seldom quotes. Darwin cites Schaaffhausen for "the posterior dental portion of the jaw being always shortened" in civilised people, "and this shortening may, I presume, be safely attributed to civilised men habitually feeding on soft, cooked food, and thus using their jaws less."¹ The diet explanation is in the founding text.

Robert Wiedersheim's The Structure of Man (1895), the source of the famous list, said the same. Citing Rose, he held that human molars derive from four- and five-cusped types "and that the numerical reduction of these cusps has been due to Man's adoption of a more delicate diet."³ "In the third molar, the so-called wisdom tooth, the process of reduction may go so far that finally, instead of a tooth with four or five cusps, a vestigial stump alone appears. In a relatively large number of cases, indeed, no wisdom tooth at all appears, it being either not formed, or, if formed, retained within the gum."³ The wisdom teeth sit in section B of his conspectus, among the organs that have "become wholly or in part functionless."³ The preface to the English edition adds the fossil comparison: in Palaeolithic jaws "the crowns of the 'wisdom teeth' are as large as, if not a trifle larger than those of the other molars in front of them."³

The claim persists unchanged. Bergman quotes a 1942 textbook calling the last molars "in man approaching a vestigial condition" and a 1943 dental monograph calling the lower third molar "a vestigial organ without purpose and function."²⁰ In November 2016 five authors in Scientific American, Michael Shermer writing the section, listed "useless vestigial structures—a distinctive sign of our evolutionary ancestry—such as wisdom teeth, male nipples, body hair, the appendix and the coccyx."⁴ Carter's 2016 Harvard dissertation opens by calling the third molar "a commonly used example for explaining why humans are still evolving and the relevance of evolutionary medicine."⁷

So three claims travel together. The tooth is useless. The tooth is a reduced copy of a larger ancestral molar. The jaw shrank faster than the teeth, so the last one no longer fits. The parent article shows the first is not the live definition. The rest of this article takes the second and third in turn, and the third first, because it is the one with an experiment behind it.

Part 2: What the numbers say

Agenesis. Kathleen Carter and Steven Worthington screened 12,376 records and pooled 92 studies with 63,314 subjects. "The worldwide rate of agenesis was found to be 22.63% (95% confidence interval = 20.64% to 24.76%), although the estimates ranged from 5.32% to 56.0%."⁵ Women were 14 percent more likely than men to lack at least one, the upper jaw 36 percent more likely than the lower, and missing one or two teeth was far commoner than missing three or four.⁵ A single Malaysian series of 5,923 radiographs found 38.4 percent.²¹

Impaction. The same authors pooled 49 radiographic studies with 83,484 adults. "Worldwide M3 impaction prevalence was found to be 24.40% (95% confidence interval [95% CI]: 18.97% to 30.80%)."⁶ The odds were 57.58 percent higher in the lower jaw, and mesioangular tilt (the crown leaning forward into the second molar) was the commonest form at 41.17 percent.⁶ They flag the sample: "Selection bias was evident because individuals had to undergo radiographic examination to be included in the analysis."⁶ Single populations run higher. Thomas Dodson and Srinivas Susarla's BMJ Clinical Evidence review, citing Hugoson and Kugelberg's 1988 Swedish survey, states that "more than 72% of Swedish people aged 20 to 30 years have at least one impacted lower wisdom tooth."²²

Timing. Wisdom teeth "generally erupt between the ages of 17 and 26 years."¹⁸ Darwin's "seventeenth year" was right. What the meta-analyses cannot show is that impaction at 18 is not a life sentence. In the Dunedin birth cohort, 821 people were examined at 18 and 26. "Of the teeth that were impacted by age 18, 33.7% had fully erupted by age 26, 31.4% had been extracted, and 13.1% remained unerupted."¹⁹ The authors concluded that "radiographically apparent impaction in late adolescence should not be sufficient grounds for their prophylactic removal in the absence of other clinical indications."¹⁹ In Helsinki students followed from 20 to 32, "22% of third molars erupted, a few even after 26 years of age; the percentage of third molars removed was 42%."²³

How many people have all four working? No source found tabulates it. The pieces are these: about one person in five lacks at least one; about one in four has at least one impacted; and Carter's upper bound for any third-molar problem is "up to 70% of modern humans."⁷ Ungar's popular figure that "three quarters of us have wisdom teeth that do not have enough room to emerge properly"² is three times the pooled impaction rate and should not be repeated as a measurement.

The two numbers have different histories, and this is the article's hinge. Carter tested three explanations for agenesis (selection against impaction, developmental delay, and Brace's probable mutation effect) on four populations sampled before, during and after the shift to farming, and two across industrialisation. Her abstract: "Agenesis dates back to at least early Homo erectus, and is seen with greater frequency during the evolution of later Homo. However, there are currently few data that support any of the three hypotheses."⁷ Her result: selection against impaction "contributed to the rise in third molar agenesis at the end of the industrial transition, but impaction remained at such low frequencies during the agricultural transition that this mechanism is unlikely to have been a causative force."⁷ "Overall, these data suggest that two different mechanisms influenced the prevalence of human third molar agenesis: one operating since the time of Homo erectus and one with much more recent origins."⁷ In short: a missing wisdom tooth is old and inherited; a stuck wisdom tooth is new.

How much newer. Carter's skeletons give the size of the change. In her Portuguese, Japanese and other archaeological series, "Industrial populations had higher (p < 0.00001) rates of M3 impaction (15.0%, 95% CI 13.0%, 17.2%) on average than agricultural populations (3.4%, 95% CI 2.6%, 4.2%)," and both sit below the 24.4 percent of modern clinical samples.⁷ That is about a fourfold rise from farmers to the industrial era, and about sevenfold to the modern X-ray samples. The rise tracks space: in both transitions the chance of impaction "decreased as maxillary ... and mandibular ... arch space increased."⁷ Two limits. Her coding was deliberately cautious, so that every specimen with roots but no crown counted as not impacted, and she calls her sample "a clear underestimate."⁷ And her earliest samples are early or part-time farmers, not hunter-gatherers, so no forager rate comes out of this study.

Part 3: The jaw shrinks in one lifetime, and the teeth do not

The experiment Darwin could not run has now been run, in the field and in the lab.

Skulls. Noreen von Cramon-Taubadel compared mandible shape across eleven global populations while controlling for shared ancestry, geography and climate. The mandible, "in contrast to the cranium, significantly reflects subsistence strategy rather than neutral genetic patterns, with hunter-gatherers having consistently longer and narrower mandibles than agriculturalists."⁸ "Agriculturalists had shorter mandibles overall, with reduced alveolar and corpus lengths, thereby diminishing the space for complete dental eruption."⁸ She is careful about cause: "it still remains to be proven conclusively whether this change is attributable to masticatory stress, weaning behavior, or other demographic factors."⁸

Ron Pinhasi, Vered Eshed and von Cramon-Taubadel then measured jaws and teeth in the same 292 skeletons from 21 sites spanning the Upper Palaeolithic to the Bronze Age in the Near East, Anatolia and Europe. Jaw shape sorted the populations by subsistence; tooth size did not. "Although later farming groups have, on average, smaller teeth and mandibles, shape analyses show that the mandibles of farmers are not simply size-reduced versions of earlier hunter-gatherer mandibles."⁹ Their conclusion dates the problem: "the lack of correlation between dental size and mandibular form that is associated with various types of malocclusion among modern-day populations, began to arise with the shift towards sedentism and agricultural subsistence practices several millennia ago."⁹ That is earlier than the Industrial Revolution date the creationist pieces give (Part 5).

David Katz, Mark Grote and Timothy Weaver fitted a quantitative-genetic model to 559 crania and 534 mandibles from 25 groups and found the effect real but small. "We detect modest directional differences between foragers and farmers. The effects are consistent with softer diets in preindustrial farming groups and are most pronounced and reliably directional when the farming class is limited to dairying populations. Diet effect magnitudes are relatively small."¹² "Mandibular size reduction in dairying populations is approximately two-thirds the magnitude of typical size differences between males and females."¹² A skeptic is entitled to that number: diet moves the jaw by less than sex does.

Living people. Robert Corruccini's work in the 1980s is the source everyone else cites. In a rural Kentucky community with almost no dental care and a recent shift from chewy to processed food, "the older inhabitants raised on more traditional diets show significantly better occlusion."²⁴ In 1984 he proposed "an epidemiologic transition" in malocclusion tracking urbanisation, which "rather throws the weight of suspicion toward environmental, not genetic, etiologic factors."²⁵

Animals. Corruccini and Robert Beecher then removed the confound. In rats, "moderate differences in the hardness of diet are related to significant differences in maxillary width and other measures of facial size."²⁶ In Science in 1982: "Among 43 squirrel monkeys (Saimiri sciureus) raised either on naturally tough or on artificially soft foods, there are significant differences in occlusal features. Animals raised on soft foods show more rotated and displaced teeth, crowded premolars, and absolutely and relatively narrower dental arches."¹⁰ The same monkeys also showed "maxillary arch narrowing, palatal arching, rotated and displaced teeth, crowded premolars, and retarded cranial bone mineralization."²⁷ Of 40 baboons, 24 fed soft food for two years of growth "showed significantly elevated variability, reduced correlations, and some disruption of normal occlusion."²⁸ Daniel Lieberman's group measured the strain directly in hyraxes: chewing raw versus cooked food produced strains "as much as two-fold at some sites," and "hyraxes raised on cooked food had significantly less growth (approximately 10%) in the ventral (inferior) and posterior portions of the face, where strains are highest."¹¹

Peter Ungar, a dental anthropologist, summed the field up in Scientific American in 2020: "Our fossil forebears did not have impacted wisdom teeth, and few appear to have had gum disease."² Crediting Corruccini, "the key change was not to the abrasive environment but to the stress environment, meaning the mechanical stresses jaws experience during eating. And the teeth were not too big—the jaw was too small."² Of the Kentucky result: "the dental differences were not genetic but environmental."²

Wear. Jaw growth is not the only way a tough diet makes room. P. R. Begg, in "Stone Age man's dentition" (1954), studied skulls of Aboriginal Australians who died before European settlement. He argued that a gritty diet wears teeth down between their contact points as well as on top, so the teeth drift forward through life and leave room at the back of the arch. Jerry Bergman's 1998 creationist paper reports Begg's case: the wear "produces mesial drift (towards the front of the mouth) because the space required to accommodate the teeth in each jaw gradually becomes less, allowing a proper fit of the third molar teeth."²⁰ Yousuke Kaifu, Kazutaka Kasai, Grant Townsend and Lindsay Richards reviewed the idea in 2003. Its claims, in their words, are that ancient dentitions changed "owing to life-long attritional tooth reduction and compensatory tooth migration," that "all contemporary humans inherit these compensatory mechanisms," and that the loss of wear in modern life leads to more dental problems. Their finding: "Available evidence, on balance, supports the first and second points of the hypothesis. As noted by many workers, the human dentition is basically 'designed' on the premise that extensive wear will occur."²⁹ The quotation marks around "designed" are theirs, and they mean fitted by evolution to a heavy-wear life. The third point, that modern dental trouble follows from the missing wear, "still needs further investigation."²⁹ So this is a second, plausible route to the same mismatch, not a measured cause of impaction. Carter adds a caution: wear rate "does not universally decrease with the adoption of agriculture."⁷

What this does and does not show. It shows that the third claim, a jaw too short for its teeth, is mostly a developmental effect of soft food, produced within one lifetime, not inherited, and reproducible in four mammal species. It does not touch the second claim. A missing tooth is not caused by a short jaw grown in childhood; agenesis is inherited and predates farming by hundreds of thousands of years on the mainstream chronology. And nothing in the soft-food experiments makes third molars smaller than second molars, which is the observation the reduction claim rests on.

Weston Price: observation and inference

Weston Price, a Cleveland dentist, spent the 1930s photographing and counting the teeth of isolated peoples and of their relatives who had taken up trade foods. Nutrition and Physical Degeneration (1939) is the source most creationist commenters reach for, so it is worth separating what he saw from what he concluded.

What he saw. Of the Indians of the far north living on their traditional diet: "There were practically no irregular teeth, including no impacted third molars, as evidenced by the fact that all individuals old enough to have the molars erupted had them standing in position and functioning normally for mastication."¹⁵ "In the new generation, after meeting the white civilization and using his foods, many developed crooked teeth, so-called, with deformed dental arches."¹⁵ Of skulls in Peruvian coastal burial grounds: "all these arches are broad and wide, that the third molars are well formed and almost always well developed, and in good masticating position."¹⁵ Of a cave burial near Cuzco: "The third molars (wisdom teeth) are well developed and in normal position for mastication. These are typical of the entire group found in this burial place."¹⁵ These observations agree with Corruccini's Kentucky series and von Cramon-Taubadel's skulls, and Price made them fifty years earlier.

What he inferred. "These data will indicate that much that we have interpreted as being due to heredity is really the result of intercepted heredity."¹⁵ Facial defects "are products of the environment rather than hereditary units transmitted from the ancestry,"¹⁵ and "these face changes occur in all the pure blood races studied in even the first generation, after the nutrition of the parents has been changed."¹⁵ "When, however, marked divergences appear without mixing of racial stocks, the result is not due to heredity, but occurs in spite of heredity."¹⁵

Three cautions. Price counted caries and looked at arches; he did not measure jaw length, and "practically no" is an impression, not a rate. His mechanism was nutritional, damage to the parents' germ cells and to the child in the womb from a diet poor in fat-soluble vitamins, and he never tested it against the alternative that the child's own chewing shapes the child's own jaw. The experiments that came later test exactly that alternative and support it. So the modern creationist gloss that wisdom-tooth trouble comes from a shortage of vitamins A, D and K2 goes beyond Price's data and past the evidence; the measured cause is mechanical load during growth. Price's observation stands; his explanation is a hypothesis that no one has confirmed.

Part 4: On the mainstream fossil series, the tooth itself shrank

The soft-food experiments explain why a normal tooth gets stuck. They do not explain why the third molar is the smallest molar in living humans and the largest in every fossil hominin, and that is the observation the reduction claim rests on.

Alistair Evans and ten colleagues measured the lower cheek teeth of modern humans and fourteen fossil hominin species for Nature in 2016. "The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions due to changes in diet or the acquisition of cooking."¹³ Their finding: "in all fossil hominins the second or third molar is the largest tooth on average,"¹³ whereas in living humans the first molar is. "Homo sapiens demonstrate a similar pattern to other species of Homo but at smaller m1 sizes, producing disproportionately decreased third molars."¹³ The mechanism they propose is developmental: an inhibitory cascade in which each molar sets the size of the next, so that one number, first-molar size, fixes the whole row. Shrink the first molar and the third shrinks most. On this model no separate loss of the wisdom tooth is needed; the row reduces as a unit and the third molar is the end of the line.

Loring Brace, Karen Rosenberg and Kevin Hunt measured the rate. From about 100,000 years ago "human tooth size began to reduce at a rate of 1% every 2,000 years,"¹⁴ and "from the beginning of the Post-Pleistocene until the present, the overall rate of dental reduction doubled, becoming approximately 1% per thousand years."¹⁴ Their explanation is not selection for smaller teeth. Cooking and then pottery "reduced the amount of selection that had previously maintained usable tooth substance," and "reduction then occurred as a consequence of the Probable Mutation Effect."¹⁴ Once big teeth stopped mattering, mutations that shrank them stopped being weeded out. No advantage for a smaller jaw or tooth is required.

Apply the parent's three-step test. Homology: the human third molar is the same tooth as the ape's and the fossil hominin's. Reduction: measured, against the teeth ahead of it and against every fossil species in the series. Ancestral distribution: here the argument stops being about teeth. Evans's and Brace's series are ancestors only if the hominin tree is accepted, which is the parent article's step 3. But note how little of the tree this case needs. Most creationist writers class Homo erectus and the Neanderthals as human. If they are, the change from a large third molar in early Homo to a small and often missing one in living people happened inside the human kind, on a timescale the sides dispute, by a mechanism they describe in nearly the same words. DeWitt calls agenesis "an example of a loss of information";³⁰ Bergman calls a smaller jaw "devolution, dysgenics caused by the accumulation of mutations";²⁰ Brace calls it the probable mutation effect. Those are three names for relaxed selection plus mutation. What remains to argue about is whether the series starts in an ape, and the wisdom tooth cannot answer that.

Part 5: The cost, the extraction controversy, and the creationist answers

The cost is real. A partly erupted third molar leaves a flap of gum that traps plaque and infects, which is pericoronitis; a forward-tilted one wedges against the second molar and rots its far surface. Distal cervical caries in the second molar "are responsible for the removal of up to 5% of all mandibular third molars," and the lesion "has been reported only in association with impacted third molars."¹⁶ Cysts and tumours of the follicle are rarer. In England and Wales removal runs at "4 per 1000 person-years," making it "one of the top 10 inpatient and day-case procedures."²²

Most of the cost is a choice. For most of the twentieth century dentists took wisdom teeth out before they caused trouble. In March 2000 the National Institute for Clinical Excellence ended that in Britain: "The practice of prophylactic removal of pathology-free impacted third molars should be discontinued in the NHS."¹⁷ Regional variation suggested that "up to 44% of wisdom teeth removals and prophylactic surgery may have been inappropriate,"¹⁷ and "a first episode of pericoronitis, unless particularly severe, should not be considered an indication for surgery."¹⁷ Twenty years on, the Cochrane review found the evidence had not grown: one randomised trial and one cohort study,¹⁸ and "insufficient evidence is available to determine whether asymptomatic disease-free impacted wisdom teeth should be removed or retained."¹⁸ Carter and Worthington close their meta-analysis with the same point: "The percentage of individuals with impacted M3s is much smaller than the percentage that undergoes clinical treatment for M3 problems."⁶ Her dissertation is blunter: clinicians treat wisdom teeth as "ticking time bombs," but "our analysis provides evidence that the majority of patients may not be at risk of impaction."⁷

Is a tooth that often causes trouble evidence against design? Only if the trouble is intrinsic to the tooth, and the evidence says it is intrinsic to the diet. Under the chewing loads the jaw grew for, the tooth erupts and works: Price's northern Indians and Peruvian skulls, Corruccini's older Kentuckians, and the pre-industrial samples in which Carter found impaction too rare to select against. A bone that grows to its load, and grows short when the load is removed, is not a defect; every bone in the body does it, and an astronaut's thinning femur is not bad design either. Two limits must be conceded. Pre-industrial impaction is low, not zero, and Pinhasi dates the mismatch to the Neolithic, so several thousand years of farmers paid part of this cost. And agenesis is not a diet effect at all; a design reading has to file it under loss, as DeWitt does.

The creationist literature in its own words. Jerry Bergman's 1998 paper is the fullest treatment. His summary: "Our better understanding of the complex teeth-jaw relationship has revealed this explanation is far too simplistic. Research now indicates that the reasons for most third molar problems today are not due to evolutionary changes but other reasons. These reasons include a change from a coarse abrasive diet to a soft western diet, lack of proper dental care, and genetic factors possibly including mutations."²⁰ His conclusion: "The most important factor is probably diet, but the influence of other factors including mutations, needs to be examined more fully to understand why wisdom teeth are more often a problem today."²⁰ Frank Sherwin (ICR, 2002): crowding "has nothing to do with macroevolution and everything to do with diet. Processed and refined foods in modern societies have resulted in our reduced use of wisdom teeth. When refined foods are constantly eaten, there is no stimulus for robust jaw development and erupting wisdom teeth become crowded."³¹ John Morris (ICR, 2002) reports that dentists trained on evolution assume the teeth are "useless evolutionary left-overs from our simian ancestry when jaws were larger."³² James Trexel, a dentist writing for Answers in Genesis in 2018, cites von Cramon-Taubadel's paper and concludes: "That impaction/disorders are increasingly frequent in today's world implies nothing about the supposed evolution of humans from primates or a supposed poor design. Wisdom teeth are certainly not vestigial organs."³³ Brian Thomas (ICR, 2020), quoting Ungar on Corruccini: "Now that we all eat processed food, our jaws grow too small for wisdom teeth to fit, and we get cavities that most of our ancestors never had to deal with. Where's the evolution here? It's just diet."³⁴

Where they are right. On diet, entirely: the sources they cite, Corruccini, von Cramon-Taubadel and Ungar, are the sources this article cites, and those authors say the same thing. Bergman also reported Begg's wear-and-drift mechanism (Part 3), which the 2003 secular review by Kaifu and colleagues found supported in its first two points. On function: "It is now widely acknowledged that these teeth are not rudimentary or vestigial: they aid in chewing our food as do all of our other 28 teeth."²⁰ True, and it answers Wiedersheim. On Lamarck: "The loss of an organ in evolution purely as a result of disuse, also called Lamarckian Evolution, has now been thoroughly disproved,"²⁰ a fair hit on the 1943 monograph that had jaws shrinking "from a lack of function."

Where they answer the wrong claim. "They aid in chewing" meets the useless-organ definition, which the parent article shows was given up in 1982. The live definition asks whether the tooth is reduced relative to an ancestor, and on that Bergman's reply is that "it is difficult to identify what advantage a smaller jaw would have for survival."²⁰ Brace's model asks for no advantage; it is the accumulation of mutations under relaxed selection, and Bergman has restated it rather than refuted it. Trexel's date is too late: he puts the trouble's "beginnings around the Industrial Revolution in the 1700–1800s,"³³ whereas Pinhasi's skeletons put the mismatch several thousand years earlier and Carter puts agenesis in early Homo erectus. And none of the pieces engages the fossil tooth-size series. Trexel's line that "in mainstream scientific thinking, wisdom teeth in humans are regarded as nothing more than unnecessary, evolutionary leftovers"³³ describes Shermer, not Evans, Brace or Carter, who call the tooth reduced and say why.

Objections and responses

"If diet explains it, why do a fifth of people never form the tooth at all?" Diet does not explain it, and this article does not claim it does. Agenesis is inherited, is old on any chronology, and is the strongest single fact for the reduction reading. One side calls it loss of information and the other the probable mutation effect; both are saying the tooth is going.

"Humans are still evolving: agenesis is selection against impaction." Carter tested that. It holds only across the industrial transition; before that, impaction was too rare to select against. The popular story has the direction right for the last two centuries and wrong for everything earlier.

"Pre-industrial people had impacted teeth too." Some did. Carter's archaeological farmers show 3.4 percent, low but not zero, against 15.0 percent in her industrial-era skeletons,⁷ and Price's "practically no" is an impression from a dentist without a spreadsheet. Ungar's "Our fossil forebears did not have impacted wisdom teeth" is too absolute. The Cap Blanc skeleton from France, the "Magdalenian Girl," dated 13,000 to 15,000 years old on the conventional scale and long taken for a teenager, turned out on new X-rays to be a woman of 25 to 35 whose wisdom teeth were impacted: "The earliest recorded case of impacted wisdom teeth."³⁵ That is a forager, not a farmer. The Field Museum's Robert Martin read it as diet changing earlier than thought, and it rests on a museum press release, not a published study. The claim is a difference in rate, and every measured series shows it.

"The diet explanation is Lamarckism." No. Nothing is inherited. A jaw grown under low chewing load is short in that person; a child raised on tough food grows a long one. That is what Price photographed in reverse and Corruccini saw in Kentucky.

"A designed jaw should fit its teeth on any diet." Bone grows to load everywhere in the skeleton; a jaw that did not would be the anomaly. The fair form of the objection is narrower: cooking is old and the mismatch is at least Neolithic, so a design reading must accept that ordinary human diets have carried part of this cost for thousands of years. Conceded. What the objection misses is that the dentition is built for change through life. Kaifu and colleagues, no creationists, conclude that it is "basically 'designed' on the premise that extensive wear will occur," with teeth that migrate forward as they wear.²⁹ A system tuned to a heavy-wear diet is not shown to be badly made by a diet that removes the wear.

Creationist objection: "Evans and Brace assume the evolutionary tree." They do. But the part of the series this case uses runs from Homo erectus to living people, which most creationist writers accept as one kind. Within that span the reduction is measured and its mechanism is common ground. Whether the series begins in an ape is the real dispute, and the wisdom tooth is silent on it.

"The tooth is useless; removing it does no harm." Removing any working molar from a person on a modern diet does little harm. That is redundancy, not vestigiality, and it is true of the second molar too. What can be conceded is that under modern conditions the third molar is the tooth a person can most afford to lose.

"Price was a crank." His observations agree with what Corruccini, von Cramon-Taubadel and Carter measured later with calipers and statistics. His nutritional mechanism is unconfirmed and should not be cited as the finding.

Issues and unanswered questions

No population survey found gives the proportion of adults with all four third molars erupted and working. Hugoson and Kugelberg's 1988 Swedish survey may contain it; it was not obtainable.
No human study separates chewing load from nutrient intake as the cause of the shorter jaw. The animal experiments varied texture, not vitamins.
Whether third-molar agenesis tracks smaller jaws within a population, and which way causation runs, was not examined here.
No creationist writer was found who engages the fossil molar-size series or Brace's rates.
No measured impaction rate for a true hunter-gatherer sample was found. Carter's earliest series are early farmers, and the one Palaeolithic case, Cap Blanc, is known from a press release, not a published study.
Whether interproximal wear and forward drift, rather than jaw growth, made room for the third molar in heavy-wear populations is Kaifu's untested third point. The two mechanisms have not been separated in one sample.
Trexel's Nigerian figures (1.1 against 10.7 percent) were not checked at their primary.
The Carter and Worthington journal papers were read as abstracts; their full content was taken from the dissertation that contains them.

Verdict

The third molar is a reduced tooth on either side's reading: smaller than the molars ahead of it, absent in a fifth of people, and, on the mainstream series, the largest molar in every fossil hominin and the smallest in living humans. The parent article's live definition is met at steps one and two. Step three, ancestral distribution, is a question about the hominin tree, and the wisdom tooth adds nothing to it beyond a reduction inside Homo that both sides accept and describe with the same mechanism.

The diet explanation is not a rival to that reading; it answers a different claim. Darwin proposed it, Corruccini and Lieberman tested it in four species, and von Cramon-Taubadel, Pinhasi and Katz measured it in skulls. The modern epidemic of impaction is a growth effect of soft food, arising within one generation, and the cost of the tooth is mostly the cost of a diet the jaw did not grow for, plus a century of surgery that a national guideline and a Cochrane review could not justify. That removes the bad-design charge. It leaves the ancestry charge exactly where the parent article left it.

Sources

1.
Darwin, Charles. The Descent of Man, and Selection in Relation to Sex, vol. 1. John Murray. 1871. Darwin's 1871 book on human descent and on selection in relation to sex, published in two volumes; this is volume 1 of two. The article quotes it for Darwin's list of human rudiments, which includes the wisdom teeth, and for his diet explanation of the shortened jaw.
1. 1a.
  Page 26: “It appears as if the posterior molar or wisdom-teeth were tending to become rudimentary in the more civilised races of man. These teeth are rather smaller than the other molars, as is likewise the case with the corresponding teeth in the chimpanzee and orang; and they have only two separate fangs. They do not cut through the gums till about the seventeenth year, and I am assured by dentists that they are much more liable to decay, and are earlier lost, than the other teeth. It is also remarkable that they are much more liable to vary both in structure and in the period of their development than the other teeth.” ↩ ↩
2. 1b.
  Page 26: “In the Melanian races, on the other hand, the wisdom-teeth are usually furnished with three separate fangs, and are generally sound: they also differ from the other molars in size less than in the Caucasian races.” ↩
3. 1c.
  Pages 26–27: Darwin is quoting Schaaffhausen for the words in the inner quotation marks; the rest of the passage is Darwin's own. “Prof. Schaaffhausen accounts for this difference between the races by "the posterior dental portion of the jaw being always shortened" in those that are civilised, and this shortening may, I presume, be safely attributed to civilised men habitually feeding on soft, cooked food, and thus using their jaws less.” ↩ ↩
2.
Ungar, Peter S. “Why We Have So Many Problems with Our Teeth.” Scientific American 322(4):44–49. Apr 2020. A magazine feature for general readers, not a study, written by a dental anthropologist at the University of Arkansas who studies living and fossil human teeth. It was printed under the title The Trouble with Teeth. The article quotes it for the claims that fossil humans lacked impacted wisdom teeth and that Corruccini's work explains why.
1. 2a.
  “Our fossil forebears did not have impacted wisdom teeth, and few appear to have had gum disease.” ↩ ↩
2. 2b.
  Section Missing Stress: “three quarters of us have wisdom teeth that do not have enough room to emerge properly.” ↩
3. 2c.
  Section Missing Stress: “According to anthropologist Rob Corruccini of Southern Illinois University, the key change was not to the abrasive environment but to the stress environment, meaning the mechanical stresses jaws experience during eating. And the teeth were not too big—the jaw was too small.” ↩
4. 2d.
  Section Missing Stress: “Thus, the dental differences were not genetic but environmental.” ↩
3.
Wiedersheim, Robert. The Structure of Man: An Index to His Past History. Macmillan. Translated by H. Bernard and M. Bernard. 1895. A textbook of human anatomy for medical students, written by a professor at the University of Freiburg, that sets out the features linking humans with lower forms. Its English preface calls it "in no sense an exhaustive treatise." The article uses it as the source of the famous list of vestigial organs and for Wiedersheim's diet explanation of the molars.
1. 3a.
  Pages 158–159: Wiedersheim is reporting the research of Rose. “The recent researches of Rose have revealed reason for believing that the upper molars of Man have been derived from a four-cusped tooth type, and the lower from a five-cusped type, and that the numerical reduction of these cusps has been due to Man's adoption of a more delicate diet”. ↩ ↩
2. 3b.
  Page 159: “In the third molar, the so-called wisdom tooth, the process of reduction may go so far that finally, instead of a tooth with four or five cusps, a vestigial stump alone appears. In a relatively large number of cases, indeed, no wisdom tooth at all appears, it being either not formed, or, if formed, retained within the gum.” ↩
3. 3c.
  Page 202: Conspectus section B, headed "Retrogressively modified, the Organs having become wholly or in part functionless". “The wisdom teeth.” ↩
4. 3d.
  Page viii: From the preface to the English edition. “In remains from reputed Palaeolithic deposits hitherto described, in which jaws and teeth have been preserved, the crowns of the "wisdom teeth" are as large as, if not a trifle larger than those of the other molars in front of them. This greater development of the last molar is characteristic of the oldest known human jaws, but is only very rarely met with in those of recent Man.” ↩
4.
Shermer, Michael et al. “These Truths Are Not Self-Evident.” Scientific American 315(5):46–53. Nov 2016. A piece in Scientific American by five authors, printed under the print title "5 Things We Know To Be True." The article uses it for the 2016 claim that wisdom teeth are still listed among useless vestigial structures.
1. 4a.
  Section Shermer's section: “And of course, humans are replete with useless vestigial structures—a distinctive sign of our evolutionary ancestry—such as wisdom teeth, male nipples, body hair, the appendix and the coccyx.” ↩ ↩
5.
Carter, Kathleen, and Steven Worthington. “Morphologic and Demographic Predictors of Third Molar Agenesis: A Systematic Review and Meta-analysis.” Journal of Dental Research 94(7):886–894. 2015. A systematic review and meta-analysis, which combines earlier studies into one estimate. It started from 12,376 studies, kept 92 with 63,314 people, and found a worldwide rate of agenesis (a tooth that never forms) of 22.63%, with estimates from 5.32% to 56.0%. The article uses it for that rate and for the sex and jaw differences.
1. 5a.
  Section Abstract: “The worldwide rate of agenesis was found to be 22.63% (95% confidence interval = 20.64% to 24.76%), although the estimates ranged from 5.32% to 56.0%.” ↩ ↩
2. 5b.
  Section Abstract: “women are 14% more likely than men to have agenesis of ≥1 third molars and that maxillary agenesis was 36% more likely than mandibular agenesis in both sexes. Furthermore, we found that having agenesis of 1 or 2 molars was most common, while agenesis of 3 or 4 molars was least common.” ↩
6.
Carter, Kathleen, and Steven Worthington. “Predictors of Third Molar Impaction: A Systematic Review and Meta-analysis.” Journal of Dental Research 95(3):267–276. 2016. A systematic review and meta-analysis that pooled 49 studies of 83,484 people aged 17 and over who had undergone dental X-rays, to find how often wisdom teeth are impacted (blocked from coming through fully). It found a worldwide impaction rate of 24.40%, and the odds of impaction were 57.58% higher in the lower jaw. The article uses it for the impaction figure and for the authors' warning that their sample was selected.
1. 6a.
  Section Abstract: “Worldwide M3 impaction prevalence was found to be 24.40% (95% confidence interval [95% CI]: 18.97% to 30.80%).” ↩ ↩
2. 6b.
  Section Abstract: The 57.58% is a difference in the odds, not in the share of people. “The odds of M3 impaction in the mandible were 57.58% (95% CI: 43.3% to 68.3%, P < 0.0001) higher than in the maxilla ... Mesioangular impaction was most common (41.17%, 95% CI: 33.8% to 49.0%)”. ↩
3. 6c.
  Section Abstract: The authors' own warning about their sample. “Selection bias was evident because individuals had to undergo radiographic examination to be included in the analysis.” ↩
4. 6d.
  Section Abstract: “Worldwide M3 impaction prevalence is lower than previously reported. The percentage of individuals with impacted M3s is much smaller than the percentage that undergoes clinical treatment for M3 problems.” ↩
7.
Carter, Katherine E. The Evolution of Third Molar Agenesis and Impaction. Harvard University. 2016. A PhD dissertation from Harvard University on the evolution of third molar agenesis and impaction. It contains both meta-analyses in full, and the journal papers give its author's name as Kathleen Carter. The article uses it for its evidence that agenesis dates back to early Homo erectus and that impaction is recent.
1. 7a.
  Section Abstract, page iii: “Up to 70% of modern humans experience problems with their third molars, whether it is failure of proper eruption (impaction) or not erupting at all (agenesis). Thus, it is a commonly used example for explaining why humans are still evolving and the relevance of evolutionary medicine.” ↩ ↩
2. 7b.
  Section Abstract, page iii: “Agenesis dates back to at least early Homo erectus, and is seen with greater frequency during the evolution of later Homo. However, there are currently few data that support any of the three hypotheses (agenesis as selection against impaction, developmental delay, and the probable mutation effect) proposed to explain the evolution of agenesis and impaction.” ↩ ↩
3. 7c.
  Section Abstract, page v: The same words repeat on page 79. “We found the selection against impaction hypothesis contributed to the rise in third molar agenesis at the end of the industrial transition, but impaction remained at such low frequencies during the agricultural transition that this mechanism is unlikely to have been a causative force.” ↩ ↩
4. 7d.
  Section Abstract, page v: “Overall, these data suggest that two different mechanisms influenced the prevalence of human third molar agenesis: one operating since the time of Homo erectus and one with much more recent origins.” ↩
5. 7e.
  Page 68: “Given that most clinicians view wisdom teeth as "ticking time bombs" that will eventually become impacted if not removed, our analysis provides evidence that the majority of patients may not be at risk of impaction.” ↩
6. 7f.
  Page 88: “Industrial populations had higher (p < 0.00001) rates of M3 impaction (15.0%, 95% CI 13.0%, 17.2%) on average than agricultural populations (3.4%, 95% CI 2.6%, 4.2%), but these rates are below estimates of impaction frequency (24.4%, 95% CI 19.0%, 30.8%; Carter and Worthington, 2016).” Archaeological skeletons from Portugal, Japan and other series, sampled before, during and after the agricultural and industrial transitions. ↩ ↩ ↩
7. 7g.
  Page 90: “We found the probability of M3 impaction, during the agricultural transition, decreased as maxillary (p = 0.00002) and mandibular (p = 0.0019) arch space increased (Figure 14cd). This negative relationship persisted during the industrial transition for the maxilla (p < 0.00001) and mandible (p < 0.00001; Figure 14cd).” ↩
8. 7h.
  Page 118: “does not universally decrease with the adoption of agriculture”. ↩
9. 7i.
  Page 119: “Unless impaction could be definitively determined in the specimen, I coded it for this analyses as "no impaction". This means that all individuals that had evidence of roots but no crown were assumed to be not impacted, and my sample represents a clear underestimate.” ↩
8.
von Cramon-Taubadel, Noreen. “Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies.” PNAS 108(49):19546–19551. 2011. A comparison of jaw shape in 11 human populations, six farming and five hunter-gatherer, that controlled for shared population history, geography and climate. Unlike the cranium, the jaw reflected how people got their food rather than neutral genetic patterns, and hunter-gatherers had longer, narrower mandibles. The article uses it for the claim that the jaw changes with diet, while noting that the author says the cause is not yet proven.
1. 8a.
  Section Abstract: “The results demonstrate that the mandible, in contrast to the cranium, significantly reflects subsistence strategy rather than neutral genetic patterns, with hunter-gatherers having consistently longer and narrower mandibles than agriculturalists.” ↩ ↩
2. 8b.
  Section Discussion: “one of the major shape differences found was that agriculturalists had shorter mandibles overall, with reduced alveolar and corpus lengths, thereby diminishing the space for complete dental eruption.” ↩
3. 8c.
  Section Discussion: “Although it still remains to be proven conclusively whether this change is attributable to masticatory stress, weaning behavior, or other demographic factors, it appears to act in a correlated fashion globally, causing a consistent shift toward a shorter, broader mandible.” ↩
9.
Pinhasi, Ron et al. “Incongruity between affinity patterns based on mandibular and lower dental dimensions following the transition to agriculture in the Near East, Anatolia and Europe.” PLoS ONE 10(2):e0117301. 2015. A study that measured the jaws and lower teeth of 292 individuals from 21 archaeological populations in the Near East, Anatolia and Europe, from the Epipalaeolithic to the Neolithic. Jaw shape separated the groups clearly, while tooth size did not, and in farming groups teeth and jaws no longer varied together. The article uses it to date the mismatch to the shift to farming, several thousand years before the Industrial Revolution.
1. 9a.
  Section Abstract, page 1: “Although later farming groups have, on average, smaller teeth and mandibles, shape analyses show that the mandibles of farmers are not simply size-reduced versions of earlier hunter-gatherer mandibles.” ↩
2. 9b.
  Section Conclusions, page 14: “the lack of correlation between dental size and mandibular form that is associated with various types of malocclusion among modern-day populations, began to arise with the shift towards sedentism and agricultural subsistence practices several millennia ago.” ↩ ↩
10.
Corruccini, Robert S., and Robert M. Beecher. “Occlusal variation related to soft diet in a nonhuman primate.” Science 218(4567):74–76. 1982. A study of 43 squirrel monkeys raised on either naturally tough food or artificially soft food, comparing how their teeth meet (occlusion) and how wide their dental arches were. The soft-fed monkeys had more rotated and displaced teeth, crowded premolars and narrower arches, and the authors write that diet consistency may be a determinant of occlusal health. The article uses it as the monkey evidence that soft food narrows the jaws, and the study is of monkeys, not people.
1. 10a.
  Section Abstract: “Among 43 squirrel monkeys (Saimiri sciureus) raised either on naturally tough or on artificially soft foods, there are significant differences in occlusal features. Animals raised on soft foods show more rotated and displaced teeth, crowded premolars, and absolutely and relatively narrower dental arches. Dietary consistency may be a determinant of occlusal health.” ↩ ↩
11.
Lieberman, Daniel E. et al. “Effects of food processing on masticatory strain and craniofacial growth in a retrognathic face.” Journal of Human Evolution 46(6):655–677. 2004. A 2004 experiment on rock hyraxes, animals with a set-back face, unlike the long-snouted monkeys, rodents and pigs used in most earlier tests. The hyraxes were fed raw or dried food or cooked food; chewing raw food produced strains as much as two-fold higher at some sites, and hyraxes raised on cooked food grew about 10 percent less in the lower and back parts of the face. The article cites it for that hyrax result, and the study is of hyraxes, not humans.
1. 11a.
  Section Abstract: “In general, higher strains, as much as two-fold at some sites, are generated by masticating raw versus cooked food. Hyraxes raised on cooked food had significantly less growth (approximately 10%) in the ventral (inferior) and posterior portions of the face, where strains are highest, resembling many of the differences evident between humans raised on highly processed versus less processed diets.” ↩ ↩
12.
Katz, David C. et al. “Changes in human skull morphology across the agricultural transition are consistent with softer diets in preindustrial farming groups.” PNAS 114(34):9050–9055. 2017. A study of preindustrial forager and farmer skulls: 559 crania from 25 groups and 534 mandibles from 24 groups, analysed with a quantitative-genetic model that accounts for how the populations are related. It found modest differences that fit softer diets among farmers, most pronounced in dairying populations. The article uses it for the point that the diet effect is real but small.
1. 12a.
  Section Abstract: “We detect modest directional differences between foragers and farmers. The effects are consistent with softer diets in preindustrial farming groups and are most pronounced and reliably directional when the farming class is limited to dairying populations. Diet effect magnitudes are relatively small, affirming the primary role of neutral evolutionary processes”. ↩ ↩
2. 12b.
  Section Results: “Mandibular size reduction in dairying populations is approximately two-thirds the magnitude of typical size differences between males and females.” ↩
13.
Evans, Alistair R. et al. “A simple rule governs the evolution and development of hominin tooth size.” Nature 530:477–480. 2016. A 2016 Nature paper that analysed tooth sizes from 58 to 66 modern human populations for each molar and from fourteen fossil hominin species. It tests a developmental rule, the "inhibitory cascade", in which the size of each tooth is set by the teeth that form before it, and it reports that the first three lower cheek teeth fit that rule in every fossil species. The article uses it for the finding that in all fossil hominins the second or third molar is the largest tooth on average, while in modern humans the first molar is.
1. 13a.
  Section Abstract: “The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions due to changes in diet or the acquisition of cooking”. ↩
2. 13b.
  Section Main text: “However, in all fossil hominins the second or third molar is the largest tooth on average.” ↩ ↩
3. 13c.
  Section Main text: “Homo sapiens demonstrate a similar pattern to other species of Homo but at smaller m1 sizes, producing disproportionately decreased third molars.” ↩ ↩
14.
Brace, C. Loring et al. “Gradual change in human tooth size in the Late Pleistocene and Post-Pleistocene.” Evolution 41(4):705–720. 1987. A 1987 paper in the journal Evolution that traces human tooth size over roughly the last 100,000 years. It reports that the rates of reduction after the Pleistocene were the same in Europe, the Middle East, China, Japan and Southeast Asia, and it credits cooking and then pottery with weakening the selection that had kept teeth large, which the authors call the Probable Mutation Effect, a process that takes over once selection no longer keeps teeth large. The article uses its rates for the reduction claim, which it says stands or falls with the hominin tree.
1. 14a.
  Section Abstract: “Starting with the onset of the last glaciation approximately 100,000 years ago and continuing to the end of the Late Pleistocene approximately 10,000 years ago, human tooth size began to reduce at a rate of 1% every 2,000 years.” ↩ ↩
2. 14b.
  Section Abstract: “From the beginning of the Post-Pleistocene until the present, the overall rate of dental reduction doubled, becoming approximately 1% per thousand years.” ↩ ↩
3. 14c.
  Section Abstract: “The use of pottery within the last 10,000 years further reduced the amount of selection that had previously maintained usable tooth substance. Reduction then occurred as a consequence of the Probable Mutation Effect (Brace, 1963; McKee, 1984).” ↩
15.
Price, Weston A. Nutrition and Physical Degeneration: A Comparison of Primitive and Modern Diets and Their Effects. Paul B. Hoeber. 1939. A 1939 book by Weston A. Price, a dentist, about his travels in the 1920s and 1930s among isolated peoples who ate traditional diets, and among the same peoples after they took up processed foods. The article uses it as the first observer of the pattern: no impacted third molars among isolated northern Indians, and crooked teeth in the new generation after they began using the foods of white civilization.
1. 15a.
  Page 78: “The physiques of the Indians of the far north who are still living in their isolated locations and in accordance with their accumulated wisdom were superb. There were practically no irregular teeth, including no impacted third molars, as evidenced by the fact that all individuals old enough to have the molars erupted had them standing in position and functioning normally for mastication.” ↩ ↩
2. 15b.
  Page 78: “In the new generation, after meeting the white civilization and using his foods, many developed crooked teeth, so-called, with deformed dental arches, as seen in Fig. 19.” ↩ ↩
3. 15c.
  Page 226: “It will be noted that all these arches are broad and wide, that the third molars are well formed and almost always well developed, and in good masticating position.” ↩
4. 15d.
  Page 239: “The third molars (wisdom teeth) are well developed and in normal position for mastication. These are typical of the entire group found in this burial place.” ↩
5. 15e.
  Page 3: “These data will indicate that much that we have interpreted as being due to heredity is really the result of intercepted heredity.” ↩ ↩
6. 15f.
  Page 3: “Such structural defects usually are not hereditary factors even though they appear in other members of the family or parents. They are products of the environment rather than hereditary units transmitted from the ancestry.” ↩
7. 15g.
  Page 4: “It will be seen that these face changes occur in all the pure blood races studied in even the first generation, after the nutrition of the parents has been changed.” ↩
8. 15h.
  Page 302: “When, however, marked divergences appear without mixing of racial stocks, the result is not due to heredity, but occurs in spite of heredity.” ↩
16.
McArdle, Louis W., and Tara F. Renton. “Distal cervical caries in the mandibular second molar: an indication for the prophylactic removal of the third molar?” British Journal of Oral and Maxillofacial Surgery 44(1):42–45. 2006. A review of the records of 100 patients from a London dental institute who had 122 lower third molars removed because of decay on the second molar behind them. Eighty-two percent of the third molars were tilted forward (mesial angulation) between 40 degrees and 80 degrees, and the abstract reports that this decay has been seen only alongside impacted third molars. The article uses the paper's figure that this decay drives up to 5% of lower third-molar removals.
1. 16a.
  Section Abstract: “Distal cervical caries (DCC) in mandibular second molar teeth are responsible for the removal of up to 5% of all mandibular third molars.” “Distal cervical caries is a late phenomenon and has been reported only in association with impacted third molars.” ↩ ↩
17.
National Institute for Clinical Excellence. “Guidance on the extraction of wisdom teeth.” Technology appraisal guidance TA1. Mar 27, 2000. Guidance issued by a British national health agency, based on a review of the evidence, that tells the NHS how to handle impacted wisdom teeth. It said that impacted third molars showing no disease should not be removed in advance, and that removal should be limited to teeth showing disease. The article uses it as the point where Britain ended routine removal of wisdom teeth.
1. 17a.
  Paragraph 1.1: “The practice of prophylactic removal of pathology-free impacted third molars should be discontinued in the NHS.” ↩ ↩
2. 17b.
  Paragraph 1.4: “The evidence suggests that a first episode of pericoronitis, unless particularly severe, should not be considered an indication for surgery. Second or subsequent episodes should be considered the appropriate indication for surgery.” ↩
3. 17c.
  Paragraph 2.2: “Wide variations in the rates of this latter procedure across the country, which suggest that in the past, up to 44% of wisdom teeth removals and prophylactic surgery may have been inappropriate, have been reported.” ↩
18.
Ghaeminia, Hossein et al. “Surgical removal versus retention for the management of asymptomatic disease-free impacted wisdom teeth.” Cochrane Database of Systematic Reviews (5):CD003879. 2020. A Cochrane systematic review, updated in 2020, that searched the literature up to 10 May 2019 and found only two studies: a randomised trial at a UK dental hospital with 77 analysed adolescents who had completed treatment with braces, and a prospective cohort study of 416 men aged 24 to 84 at a private US dental clinic. Both studies were judged to be at risk of bias, and the reviewers concluded that the evidence was insufficient to say whether asymptomatic disease-free impacted wisdom teeth should be removed or retained. The article uses that verdict to show that the evidence had not grown in the twenty years after NICE's 2000 guidance.
1. 18a.
  Section Background: “Wisdom teeth, or third molars, generally erupt between the ages of 17 and 26 years (Venta 1999; Kruger 2001).” ↩
2. 18b.
  Section Main results: “This review update includes the same two studies that were identified in our previous version of the review: one RCT with a parallel-group design, which was conducted in a dental hospital setting in the United Kingdom, and one prospective cohort study, which was conducted in the private sector in the USA.” ↩
3. 18c.
  Section Authors' conclusions: “Insufficient evidence is available to determine whether asymptomatic disease-free impacted wisdom teeth should be removed or retained.” ↩ ↩
19.
Kruger, Estie et al. “Third molar outcomes from age 18 to 26: findings from a population-based New Zealand longitudinal study.” Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics 92(2):150–155. 2001. A population-based prospective cohort study in New Zealand, in which eight hundred twenty-one people were examined at ages 18 and 26. Panoramic X-rays at 18 recorded 2,857 third molars, and 92.8% of them could be followed clinically at 26. The article uses it to show that many teeth impacted at 18 still erupt, so impaction in late adolescence is not a life sentence.
1. 19a.
  Section Abstract: “Of the teeth that were impacted by age 18, 33.7% had fully erupted by age 26, 31.4% had been extracted, and 13.1% remained unerupted.” ↩ ↩
2. 19b.
  Section Abstract: “radiographically apparent impaction in late adolescence should not be sufficient grounds for their prophylactic removal in the absence of other clinical indications.” ↩
20.
Bergman, Jerry. “Are wisdom teeth (third molars) vestiges of human evolution?” CEN Technical Journal 12(3):297–304. 1998. An eight-page essay that reviews the literature and argues that wisdom teeth are not vestigial organs left over from evolution. It was posted on creation.com, a creationist website. It quotes a 1942 textbook and a 1943 book on the impacted lower third molar, both of which called the teeth vestigial, and it argues that today's impaction (a tooth blocked from coming through fully) is mainly caused by diet, with poor dental care and possibly genetic factors. The article calls it the fullest creationist treatment of the question.
1. 20a.
  Page 297: The summary at the start of the paper. “Our better understanding of the complex teeth-jaw relationship has revealed this explanation is far too simplistic. Research now indicates that the reasons for most third molar problems today are not due to evolutionary changes but other reasons. These reasons include a change from a coarse abrasive diet to a soft western diet, lack of proper dental care, and genetic factors possibly including mutations.” ↩
2. 20b.
  Page 297: Quoting Rogers, Hubbell and Byers, Man and the Biological World (1942), p. 313. “The "wisdom teeth," or last molars, are in man approaching a vestigial condition”. Quoting Durbeck, The Impacted Lower Third Molar (1943). “the lower third molar occupies an abnormal position and may be considered a vestigial organ without purpose and function.” ↩
3. 20c.
  Page 297: “The loss of an organ in evolution purely as a result of disuse, also called Lamarckian Evolution, has now been thoroughly disproved.” ↩
4. 20d.
  Page 298: “A major problem with this belief is it is difficult to identify what advantage a smaller jaw would have for survival. Evolution of a smaller jaw would at best be a result of devolution, dysgenics caused by the accumulation of mutations.” ↩ ↩ ↩
5. 20e.
  Page 298: “It is now widely acknowledged that these teeth are not rudimentary or vestigial: they aid in chewing our food as do all of our other 28 teeth.” ↩
6. 20f.
  Page 302: From the paper's conclusions. “The most important factor is probably diet, but the influence of other factors including mutations, needs to be examined more fully to understand why wisdom teeth are more often a problem today.” ↩ ↩
7. 20g.
  Page 301: Bergman is summarising P. R. Begg, Stone Age man's dentition, American Journal of Orthodontics 40 (1954). “The result of teeth wear produces mesial drift (towards the front of the mouth) because the space required to accommodate the teeth in each jaw gradually becomes less, allowing a proper fit of the third molar teeth.” ↩
21.
Sujon, Mamun Khan et al. “Prevalence of Third Molar Agenesis: Associated Dental Anomalies in Non-Syndromic 5923 Patients.” PLoS ONE 11(8):e0162070. 2016. A retrospective study of panoramic X-rays from 5923 patients aged 10 to 50 at two diagnostic centers in Dhaka, Bangladesh. The authors say agenesis rates vary between geographic regions. The article uses its figure of 38.4% as one example from a single population.
1. 21a.
  Section Abstract: “The prevalence of third molar agenesis was 38.4%.” ↩
22.
Dodson, Thomas B., and Srinivas M. Susarla. “Impacted wisdom teeth.” BMJ Clinical Evidence. 2014. A systematic review for BMJ Clinical Evidence, article 2014:1302, written by a University of Washington dentist and a plastic surgeon at Johns Hopkins Hospital. The authors searched medical databases up to October 2013 and found 11 studies that met their criteria, on whether symptom-free impacted wisdom teeth should be removed in advance and which surgical methods work best. The article uses it for the Swedish figure of 72% and for the removal rate in England and Wales.
1. 22a.
  Section Incidence/Prevalence: The review takes this figure from Hugoson and Kugelberg, Community Dental Health 5:121–138, 1988. “More than 72% of Swedish people aged 20 to 30 years have at least one impacted lower wisdom tooth.” ↩
2. 22b.
  Section Incidence/Prevalence: “The incidence of wisdom tooth removal is estimated to be 4 per 1000 person-years in England and Wales, making it one of the top 10 inpatient and day-case procedures.” ↩
23.
Ventä, Irja et al. “Change in clinical status of third molars in adults during 12 years of observation.” Journal of Oral and Maxillofacial Surgery 57(4):386–389. 1999. A follow-up study of 81 university students (32 men and 49 women) at the University of Helsinki, examined and X-rayed at a mean age of 20.7 and again at 32.6. Of their third molars, 22% erupted over the 12 years, some after age 26, and 42% were removed. The article uses it to show that the third molars of young adults keep changing, and some still erupt, after the teens.
1. 23a.
  Section Abstract: “During the 12-year follow-up, 22% of third molars erupted, a few even after 26 years of age; the percentage of third molars removed was 42%.” ↩
24.
Corruccini, Robert S., and Larry D. Whitley. “Occlusal variation in a rural Kentucky community.” American Journal of Orthodontics 79(3):250–262. 1981. An epidemiologic study of thirty-four people in a rural central Kentucky community with almost no professional dental care, whose diet had included many hard-to-chew foods until industry arrived. Occlusion was evaluated with the Treatment Priority Index from wax-bite impressions and dietary histories, and the authors call dietary consistency the most powerful explanation but say the data were not conclusive. The article calls it the source that later writers cite for diet and bites in living people.
1. 24a.
  Section Abstract: “The older inhabitants raised on more traditional diets show significantly better occlusion. Dietary consistency provides the most powerful explanation for the transition in occlusal variation, through it was not conclusive in these data.” The source prints "through" for "though" (sic). ↩
25.
Corruccini, Robert S. “An epidemiologic transition in dental occlusion in world populations.” American Journal of Orthodontics 86(5):419–426. 1984. Its abstract sets out a model rather than reporting a sample, and compares malocclusion with the epidemiologic transition seen in diabetes and coronary heart disease as societies undergo modernization. Corruccini proposes that malocclusion rises with urbanization, and that the speed of the rise is proportional to the speed of urban change, which points toward environmental causes. The article cites it for the 1984 proposal that malocclusion tracks urbanization.
1. 25a.
  Section Abstract: “I suggest that an equally clearly defined epidemiologic transition characterizes malaligned and discrepant dental occlusal relations in western societies, and others undergoing urbanization, and that the rapidity of the transition is proportional to the rapidity of urbanizational change. This phenomenon rather throws the weight of suspicion toward environmental, not genetic, etiologic factors.” ↩
26.
Beecher, Robert M., and Robert S. Corruccini. “Effects of dietary consistency on craniofacial and occlusal development in the rat.” Angle Orthodontist 51(1):61–69. 1981. A study of how the hardness of the diet affects the face and bite of developing rats. The abstract reports that moderate differences in diet hardness go with significant differences in the width of the upper jaw and other measures of facial size, and it suggests that the muscle work of chewing helps coordinate facial growth. The article cites it as the rat evidence that diet hardness changes facial width.
1. 26a.
  Section Abstract: “Moderate differences in the hardness of diet are related to significant differences in maxillary width and other measures of facial size.” ↩
27.
Beecher, Robert M. et al. “Craniofacial correlates of dietary consistency in a nonhuman primate.” Journal of Craniofacial Genetics and Developmental Biology 3(2):193–202. 1983. Forty-three squirrel monkeys were raised on either naturally tough or artificially softened foods in this 1983 study. The soft-fed animals had a narrowed upper arch, palatal arching, rotated and displaced teeth, crowded premolars and slower cranial bone mineralization, and the authors compare these with American children to suggest that diet consistency may matter for human facial growth. The article cites it for the list of effects in the soft-fed monkeys.
1. 27a.
  Section Abstract: The latter means the monkeys raised on artificially softened food. “The latter exhibit maxillary arch narrowing, palatal arching, rotated and displaced teeth, crowded premolars, and retarded cranial bone mineralization.” ↩
28.
Corruccini, Robert S., and Robert M. Beecher. “Occlusofacial morphological integration lowered in baboons raised on soft diet.” Journal of Craniofacial Genetics and Developmental Biology 4(2):135–142. 1984. A 1984 study of 40 baboons, 24 of which were fed a soft experimental diet for two years while they were growing. Its title's "integration" means how closely the parts of the face and bite grow together, and the soft-fed baboons showed more variation, weaker links between parts and some disruption of normal occlusion (how the teeth meet). The article cites it among the animal experiments on soft diets.
1. 28a.
  Section Abstract: “Of a sample of 40 baboons, 24 were given soft experimental diet, removing masticatory stress, for a 2-year period during growth. In oral-facial and dental occlusal structures, the experimental animals showed significantly elevated variability, reduced correlations, and some disruption of normal occlusion.” ↩
29.
Kaifu, Yousuke et al. “Tooth wear and the "design" of the human dentition: a perspective from evolutionary medicine.” American Journal of Physical Anthropology (Yearbook of Physical Anthropology 46) 122(S37):47–61. 2003. A review by dental anthropologists and orthodontists of the attritional-occlusion hypothesis from the 1950s, that teeth in heavy-wear populations wear between their contacts and drift forward through life. It finds the evidence supports the hypothesis that ancient dentitions worked this way and that living people inherit the mechanism, and leaves open whether the lack of wear causes modern dental problems. The article uses it as a secular statement that the human dentition is built for heavy wear.
1. 29a.
  Section Abstract, page 47: “Available evidence, on balance, supports the first and second points of the hypothesis. As noted by many workers, the human dentition is basically "designed" on the premise that extensive wear will occur”. The first point is that ancient dentitions changed "owing to life-long attritional tooth reduction and compensatory tooth migration"; the second, that "all contemporary humans inherit these compensatory mechanisms." ↩ ↩
2. 29b.
  Section Abstract, page 47: “Some dental problems in contemporary societies appear to reflect the disparity between the original design of our dentition and our present environment, in which extensive wear no longer occurs, but this possibility still needs further investigation.” ↩
30.
DeWitt, David A. “Setting the Record Straight on Vestigial Organs.” Answers in Genesis. 2008. A 2008 web article on the creationist Answers in Genesis site, written as a reply to a New Scientist article that called five human organs useless relics of our evolutionary past. Its wisdom-teeth section reports the New Scientist figure that about 35 percent of people do not develop wisdom teeth, and says that if the figure is right it is a loss of information, not proof that the teeth are useless. The article uses it for the creationist claim that smaller jaws, perhaps from diet, are one reason wisdom teeth cause trouble.
1. 30a.
  Section Wisdom Teeth: “it is an example of a loss of information, the opposite of what molecules-to-man evolution requires”. “One of the reasons that they are problematic is the decreased jaw size of many people today which may be related to diet.” ↩
31.
Sherwin, Frank. “The Whole Tooth about Wisdom Teeth.” Acts & Facts 31(3). 2002. An Institute for Creation Research magazine article by Frank Sherwin, D.Sc. (hon.), which criticises a popular 2002 high school biology textbook for presenting wisdom-tooth removal as caused by evolution of the human jaw. It argues that the cause is diet, because refined food gives the jaw no reason to grow and the wisdom teeth crowd. The article quotes it among creationist writers; its web page is dated 1 March 2003, but the magazine citation gives 2002.
1. 31a.
  Paragraph 1: “But this has nothing to do with macroevolution and everything to do with diet. Processed and refined foods in modern societies have resulted in our reduced use of wisdom teeth. When refined foods are constantly eaten, there is no stimulus for robust jaw development and erupting wisdom teeth become crowded.” ↩
32.
Morris, John D. “Is Lack of Room for Wisdom Teeth Proof of Evolution?” Acts & Facts 31(3). Mar 1, 2002. An Institute for Creation Research article by John D. Morris, Ph.D., arguing that losing room for wisdom teeth cannot show evolution, because evolution should explain new structures and not their loss. It blames western food, possibly faster maturing with too little facial growth time, poor nutrition, and infant sleeping positions, and it calls healthy wisdom teeth gifts from the Creator. The article quotes it among creationist writers.
1. 32a.
  Paragraph 1: “Based on evolutionary training, many dentists assume that wisdom teeth are "vestigial," useless evolutionary left-overs from our simian ancestry when jaws were larger.” ↩
33.
Trexel, James R. “Are Wisdom Teeth Evidence for Evolution?” Answers in Genesis. Jan 27, 2018. An essay on the Answers in Genesis website by James R. Trexel, DDS, a dentist who says he has removed dozens of wisdom teeth. It argues that coarse food once wore teeth down and grew larger jaws, so the wisdom teeth fitted, and that a processed modern diet has shrunk jaws and made impaction common. The article quotes it for the claim that the trouble began with the Industrial Revolution, and it disputes that date.
1. 33a.
  “In mainstream scientific thinking, wisdom teeth in humans are regarded as nothing more than unnecessary, evolutionary leftovers, useless remnants of mutation and natural selection.” ↩
2. 33b.
  “Humans having problems with space for wisdom teeth and/or wisdom tooth impaction is a recent phenomenon, having its beginnings around the Industrial Revolution in the 1700–1800s.” ↩
3. 33c.
  “That impaction/disorders are increasingly frequent in today's world implies nothing about the supposed evolution of humans from primates or a supposed poor design. Wisdom teeth are certainly not vestigial organs.” ↩
34.
Thomas, Brian. “Do Our Wisdom Teeth Show Poor Design?” ICR Creation Science Update. Apr 28, 2020. A piece from the ICR Creation Science Update series by Brian Thomas on whether wisdom teeth show poor design. The article quotes it among creationist writers, and it puts the whole problem down to diet.
1. 34a.
  “Peoples around the world who once ate tough stuff had healthy teeth and jaws for millennia. Now that we all eat processed food, our jaws grow too small for wisdom teeth to fit, and we get cavities that most of our ancestors never had to deal with. Where's the evolution here? It's just diet.” ↩
35.
Field Museum. “15,000-year-old Early Modern Human Skeleton Has Oldest Recorded Case Of Impacted Wisdom Teeth.” ScienceDaily. Mar 8, 2006. A museum press release, reprinted as an unsigned news item in the British Dental Journal 200(6):311, on new X-rays of the Magdalenian skeleton from the Cap Blanc rock shelter in France, held by the Field Museum since 1926. The impacted third molars showed the skeleton to be a woman of 25 to 35, not a teenager. It is a single case, announced without a peer-reviewed report. Mirror: Nature.com
1. 35a.
  Paragraph 1: “The earliest recorded case of impacted wisdom teeth belongs to the renowned "Magdalenian Girl," a nearly complete 13,000- to 15,000-year-old skeleton excavated in France in 1911and acquired by The Field Museum in 1926.” Robert D. Martin, Field Museum provost: "Finding impacted wisdom teeth 15,000 years ago indicates that the human diet might have already changed, some would say 'deteriorated,' earlier than previously thought." ↩