Atavisms

Coyne, Jerry A.  Why Evolution Is True.  Viking, New York.  2009.  A popular book on evolution.  The article uses it for the popular form of the definition of an atavism, and for Coyne's test: a true atavism must match an ancestral trait in a fairly exact way.

1. 1a.

   Page 64:  “True atavisms must recapitulate an ancestral trait, and in a fairly exact way.  They aren't simply monstrosities.  A human born with an extra leg, for example, is not an atavism because none of our ancestors had five limbs.” ↩ ↩ ↩

2. 1b.

   Page 64:  “Occasionally an individual crops up with an anomaly that looks like the reappearance of an ancestral trait.  A horse can be born with extra toes, a human baby with a tail.  These sporadically expressed remnants of ancestral features are called atavisms, from the Latin atavus, or "ancestor."” ↩

3. 1c.

   Page 64:  “The most famous genuine atavisms are probably the legs of whales.  We've already learned that some species of whales retain vestigial pelvises and rear leg bones, but about one whale in five hundred is actually born with a rear leg that protrudes outside the body wall.”  No source is given for the rate.  Andrews 1921 is the only whale-leg paper in the book's bibliography (p. 259). ↩

4. 1d.

   Page 65:  “It turns out that horse embryos begin development with three toes, which grow at equal rates.” ↩

5. 1e.

   Page 65:  “The most striking atavism in our own species is called the "coccygeal projection," better known as the human tail.”  “The tails vary tremendously: some are "soft," without bone, while others contain vertebrae— the same vertebrae normally fused together in our tailbone.” ↩

6. 1f.

   Pages 65–66:  “And they aren't just simple flaps of skin, but can have hair, muscles, blood vessels, and nerves.  Some can even wiggle!”  The page break falls after 'And they'. ↩

7. 1g.

   Page 66:  “What could this mean, other than that we still carry a developmental program for making tails?  Indeed, recent genetic work has shown that we carry exactly the same genes that make tails in animals like mice, but these genes are normally deactivated in human fetuses.  Tails appear to be true atavisms.” ↩ ↩

8. 1h.

   Page 63, figure 14:  “Bottom: atavistic tail of a three-month-old Israeli infant.  X-ray of the tail (right) shows that the three caudal vertebrae are much larger and more well developed than normal, are not fused, and approach the size of the sacral vertebrae (S1-S5).”  The words are the caption to the figure.  The credits on page 271 give the photographs as from Bar-Maor, Kesner and Kaftori, Journal of Bone and Joint Surgery 62-B:508–510, 1980. ↩

9. 1i.

   Page 66:  “Some atavisms can be produced in the laboratory.  The most amazing of these is that paragon of rarity, hen's teeth.”  “Since the underlying mouse tissue alone could not produce teeth, Kollar and Fisher inferred that molecules from the mouse reawakened a dormant developmental program for making teeth in chickens.” ↩

Darwin, Charles.  The Descent of Man, and Selection in Relation to Sex.  Volume 1.  John Murray, London.  1871.  The first volume of the first edition of Darwin's book on the descent of man and selection in relation to sex.  The article uses it for Darwin's own retreat on extra nipples: he first took them to be a return to an ancestral form, then wrote that a report of nipples on other parts of the body had greatly weakened his argument.

1. 2a.

   Page 125:  Footnote 38 in the book.  “In my 'Variation of Animals under Domestication' (vol. ii. p. 57) I attributed the not very rare cases of supernumerary mammæ in women to reversion.  I was led to this as a probable conclusion, by the additional mammæ being generally placed symmetrically on the breast, and more especially from one case, in which a single efficient mamma occurred in the inguinal region of a woman, the daughter of another woman with supernumerary mammæ.  But Prof. Preyer ('Der Kampf um das Dasein,' 1869, s. 45) states that mammæ erraticæ have been known to occur in other situations, even on the back; so that the force of my argument is greatly weakened or perhaps quite destroyed.” ↩ ↩ ↩

Hall, Brian K.  Evolutionary Developmental Biology.  Kluwer Academic, Dordrecht.  2nd edition.  1999.  A textbook on evolutionary developmental biology.  The article uses it for its definition of an atavism, and for the argument that the genes for a lost structure must survive in a silent state, or the structure could not come back.

1. 3a.

   Page 287:  “Atavisms are ancestral characters that occasionally reappear in individuals of descendant species.  This is reflected in synonyms for the word, which include 'throwbacks', 'reversions', and 'reproduction of the ancestral type'.  Atavisms are traditionally interpreted phylogenetically as the reappearance of an ancestral state.  When viewed ontogenetically they provide evidence of the retention of ancestral developmental programmes”. ↩

2. 3b.

   Page 287:  “Indeed, such atavistic reappearances tell us that loss of the structure cannot have meant loss of the developmental machinery to produce the structure.” ↩

3. 3c.

   Page 287:  “A silenced gene is defined as a gene that is no longer transcribed; i.e. the gene might still be present but inactive, as indeed it must be for an ancestral pattern to be reestablished.” ↩

4. 3d.

   Page 287:  “Perhaps the classic examples from nature are three-toed horses, hindlimb skeletons in whales, atavistic muscles in passerine birds and prolegs in insects”.  “Other examples, not discussed here, include atavistic muscles in mammals, winged earwigs, molar teeth in Pleistocene Lynx, extra nipples, tails and excess hair in humans, dew claws in dogs”. ↩ ↩

5. 3e.

   Page 289:  “Embryonic horses have primordia for three toes of equal size and development.” ↩

6. 3f.

   Page 289:  “Modern whales in the Order Cetacea are all marine but evolved from terrestrial ancestors in the Paleocene or Eocene epochs.” ↩

7. 3g.

   Page 341:  “At the individual level, atavistic characters are recognized as the continuation, in some individuals, of a developmental process that is truncated in other individuals of the population or species.” ↩

Dao, Anh H., and Martin G. Netsky.  “Human tails and pseudotails.”  Human Pathology 15(5):449–453.  1984.  A case report of a tail in a two-week-old infant, with a review of 33 earlier cases of true tails and pseudotails.  A pseudotail is a lesion that only looks like a tail.  The article uses the split into true tails and pseudotails, and the finding that true tails are rarely familial.

1. 4a.

   Section Abstract:  “The true, or persistent, vestigial tail of humans arises from the most distal remnant of the embryonic tail.  It contains adipose and connective tissue, central bundles of striated muscle, blood vessels, and nerves and is covered by skin.  Bone, cartilage, notochord, and spinal cord are lacking.  The true tail arises by retention of structures found normally in fetal development.  It may be as long as 13 cm, can move and contract, and occurs twice as often in males as in females.” ↩ ↩ ↩

2. 4b.

   Section Abstract:  “Pseudotails are varied lesions having in common a lumbosacral protrusion and a superficial resemblance to persistent vestigial tails.  The most frequent cause of a pseudotail in a series of ten cases obtained from the literature was an anomalous prolongation of the coccygeal vertebrae.” ↩

3. 4c.

   Section Abstract:  “A true tail is easily removed surgically, without residual effects.  It is rarely familial.” ↩ ↩

Lu, Frank L. et al.  “The human tail.”  Pediatric Neurology 19(3):230–233.  1998.  A case report of a tail-like lesion in a newborn, with a review of 59 cases published from 1960 to 1997.  The article uses the review's figures to show that many reported tails come with defects of the spinal cord.

1. 5a.

   Section Abstract:  “In reviewing the literature from 1960 to 1997, 59 cases were described.  Higher incidences of spinal dysraphism (49.15%) and tethered spinal cord (20.34%) compared with previous reports were evident.” ↩ ↩ ↩

Wilkinson, C. Corbett, and Alexander J. Boylan.  “Proposed caudal appendage classification system; spinal cord tethering associated with sacrococcygeal eversion.”  Child's Nervous System 33(1):69–89.  2017.  A review of every caudal appendage seen by the pediatric neurosurgeons of Children's Hospital Colorado from 2000, with a review of the literature.  It found nine appendages that the 1984 Dao and Netsky scheme calls true tails, all with a tethered or possibly tethered spinal cord, and proposed a new five-category scheme to replace the true-tail and pseudotail split.  It matters here because it is a surgical series, not a single case, and because its authors reject the embryonic-remnant reading.

1. 6a.

   Section Abstract, Results and Conclusions:  “We found 9 "true" tails (as classified by the most commonly used system).  All 9 were associated with tethering or possible tethering of the spinal cord and 6 were associated with a low-lying conus medullaris.”  “Most so-called true tails are likely cutaneous markers for spinal dysraphism and spinal cord tethering and are not remnants of the embryonic human tail.” ↩ ↩ ↩

Tojima, Sayaka et al.  “Tail reduction process during human embryonic development.”  Journal of Anatomy 232(5):806–811.  2018.  An embryology study from the Kyoto Collection, the largest collection of human embryos.  The team reconstructed every somite in three dimensions in 42 embryos from Carnegie stages 13 to 23 and counted the somite pairs in the tail region at each stage.  It found that somites run to the tip of the embryonic tail, which removes the boneless tail tip that older accounts used to explain boneless tails at birth, and it says whether those tails come from the embryonic tail is unknown.  Mirror:  PMC

1. 7a.

   Section Abstract:  “Although the human tail is completely absent at birth, the embryonic tail is formed just as in other tailed amniotes.” ↩

2. 7b.

   Section Discussion, Is the ‘human tail’ really a vestige of the embryonic tail?:  “However, we found that caudal somites were distributed throughout the tail to the tip during development; thus, we showed that the ‘caudal filament’ without bony elements (somites) was not actually present.” ↩ ↩ ↩

3. 7c.

   Section Discussion, Is the ‘human tail’ really a vestige of the embryonic tail?:  “Additionally, to determine whether the ‘true tail’ was a vestige of the embryonic tail, more information regarding the number of total vertebrae and presence of skeletal muscle fibers homologous to caudal musculature is needed.  Unfortunately, most previous reports have lacked such information; thus, it is still unclear whether the ‘true tail’ is derived from the embryonic tail.”  In this passage "true tail" follows Dao and Netsky's usage, the boneless appendage. ↩ ↩

Mimouni, F. et al.  “Occurrence of supernumerary nipples in newborns.”  American Journal of Diseases of Children 137(10):952–953.  1983.  A prospective study of 1,691 consecutively born newborns, using a new technique to find extra nipples.  It found one case in 40 births, and no link between extra nipples and other birth defects.  The article uses the rate of one in 40 to show that extra nipples are too common to meet the "extreme rarity" test that an atavism must pass.

1. 8a.

   Section Abstract:  “A prospective study on supernumerary nipples (SNNs) was performed on 1,691 consecutively born neonates.”  “The incidence of this anomaly was one per 40 or 25 per 1,000 live births.” ↩ ↩

Shapiro, Liza J. et al.  “Human quadrupeds, primate quadrupedalism, and Uner Tan Syndrome.”  PLOS ONE 9(7):e101758.  Jul 2014.  A gait study that measured 518 quadrupedal strides from video of people with Uner Tan Syndrome.  Its authors found that the walk was almost always the lateral sequence, not the primate diagonal sequence, and that it resembles the walk of healthy adults asked to walk on all fours in an experiment.  The article uses it to show that the walk is not primate-like and needs no evolutionary explanation.

1. 9a.

   Page 2:  “To date, there has been no response to the repeated claims that the people with UTS are using primate-like diagonal sequence quadrupedalism, despite the fact that Tan and colleagues have never presented data supporting this key element of their "devolution" hypothesis.” ↩

2. 9b.

   Page 4:  “Contrary to the published claims that the Turkish individuals with UTS used "primate-like" (DSDC) walking gaits, only 1% of the 513 strides quantified across Participants 1–5 from Family "A" were categorized as DSDC.  Rather, these participants nearly exclusively (98.6% of strides) walked in lateral sequence.”  The abstract gives 518 strides for the whole study; 513 are from the first family.  DSDC means diagonal sequence, diagonal couplets, the gait primates prefer. ↩ ↩

3. 9c.

   Page 8:  “We conclude that although the habitual use of quadrupedalism by adults with UTS is unusual, the form of this quadrupedalism resembles that of healthy adults and is thus not at all unexpected.  As we have shown, quadrupedalism in healthy adults or those with a physical disability can be explained using biomechanical principles rather than evolutionary assumptions.” ↩

Theobald, Douglas L.  “29+ Evidences for Macroevolution, Part 2: Past History.”  TalkOrigins Archive.  2012.  A web essay in the TalkOrigins Archive that lists evidence for macroevolution, here its section on atavisms.  It gives three features that mark an atavism and examples: human tails, a dolphin's limbs and a primate tail with no vertebrae.  The article uses the three features and checks each example against them.

1. 10a.

   Section Prediction 2.2:  “Atavisms have several essential features: (1) presence in adult stages of life, (2) absence in parents or recent ancestors, and (3) extreme rarity in a population (Hall 1984).” ↩

2. 10b.

   Section Example 2:  “Although human tails usually lack skeletal structures (some medical articles have claimed that true tails never have vertebrae), several human tails have also been found with cartilage and up to five, well-developed, articulating vertebrae (see Figure 2.2.3; Bar-Maor et al. 1980; Dao and Netsky 1984; Fara 1977; Sugumata et al. 1988).” ↩

3. 10c.

   Section Example 2:  “However, caudal vertebrae are not a necessary component of mammalian tails.  Contrary to what is frequently reported in the medical literature, there is at least one known example of a primate tail that lacks vertebrae, as found in the rudimentary two-inch-long tail of Macaca sylvanus (the "Barbary ape")”. ↩

4. 10d.

   Section Example 1:  “These limbs are prima facie evidence of the dolphin's four-limbed ancestry, as predicted from the common ancestry of dolphins and other land-dwelling mammals.” ↩

Carstanjen, Bianca et al.  “Bilateral polydactyly in a foal.”  Journal of Veterinary Science 8(2):201–203.  2007.  A veterinary case report of a 7-month-old Berber colt with an extra digit on each forelimb, which surgery removed; the horse was sound 18 months later.  The article uses the paper's two forms of horse polydactyly, a duplication and an atavistic form that grows from the splint bone, and the authors' own warning that the split is controversial.

1. 11a.

   Page 203:  “In the teratogenic form, the supernumerary digits are due to a teratogenic splitting of the basipodial elements, i.e. schistodactyly.  Most cases have all phalangeal bones affected whereas the splint bones are often normal.  In the developmental or atavistic form, the digit usually derives from the distal end of the splint bone.” ↩

2. 11b.

   Page 203:  “However, the above classification is controversial and characteristics of more than one form might be present in the same individual [13].” ↩ ↩

Woon, Jason T. et al.  “CT morphology and morphometry of the normal adult coccyx.”  European Spine Journal 22(4):863–870.  2013.  A study of pelvic CT scans from 112 adults with no known sacral or coccygeal disease, measuring the normal tailbone in living people.  Two observers read the scans and found four coccygeal segments in 76% and fusion of the sacrum to the coccyx in 57%.  The article uses the paper's range of 3 to 5 segments to show that a coccyx with three segments is normal, not extra.

1. 12a.

   Section Discussion:  “The normal adult coccyx comprises 3–5 segments, 4 being present in most individuals; a greater number of segments has been reported in a few individuals in some studies [19]”. ↩

Ermutlu, İ. et al.  “The human tail: a case series of five patients and a review of the literature.”  Child's Nervous System 41(1):375.  2025.  A case series in the journal Child's Nervous System, reviewing five children aged 6 months to 10 years whose "human tail" was surgically removed between 2000 and 2015.  Four of the five had a tethered cord, a spinal cord held down at its base, and the tissue was fat, fibrous tissue, blood vessels and nerves, with no bone or cartilage.  The article uses these findings to show that the human tail is soft tissue, often with a spinal defect beneath it.

1. 13a.

   Section Abstract, Results:  “An underlying tethered cord syndrome was identified in four of the five cases (80%).”  “Histopathology revealed mature adipose tissue, fibrous connective tissue, blood vessels, and nerve fibers, with no bone or cartilage.” ↩

Cai, Chunquan et al.  “Surgical treatment of a patient with human tail and multiple abnormalities of the spinal cord and column.”  Advances in Orthopedics 2011:153797.  2011.  A case report of one 9-month-old male infant with a human tail, a tail-like lump at the base of the spine, plus defects in the spinal cord and spine, treated by surgery and followed for 18 months.  The authors also review the embryology of the tail.  The article uses the embryology, and the authors' view that a true tail can be a benign condition with no malformation.

1. 14a.

   Section Discussion:  “During the fifth and sixth weeks, the trunk ends in a conspicuous tail containing 10–12 caudal vertebrae.  The distal portion lacks bone and is composed of mesodermal elements.  During the seventh and eighth weeks, the vertebrated portion retracts into the soft tissue.  The nonvertebrated part projects temporarily and then undergoes regression caused by phagocytosis, with the debris-laden macrophages migrating back to the body [11], and it disappears completely at the end of the eighth week.  Thus, the presence of human tail can be considered a disturbance in the development of the embryo but not a regression in the evolutionary process.” ↩

2. 14b.

   Section Discussion:  “we consider that the caudal appendage called a true tail is better thought of as being a benign condition, a prolongation beyond the coccygeal or midgluteal region, and should not be associated with any underlying malformation”. ↩

Fooden, Jack.  “Systematic review of the Barbary macaque, Macaca sylvanus (Linnaeus, 1758).”  Fieldiana Zoology, new series 113:1–58.  Oct 26, 2007.  A museum review of one primate, the Barbary macaque, published by the Field Museum of Natural History.  It measured specimens, most of them collected near Azrou in Morocco, and counted their caudal vertebrae.  The article uses it to show that the macaque's tail vestige is soft, with no vertebrae reaching into it, so a boneless tail stub exists in a living primate.

1. 15a.

   Page 6:  “In a series of 13 Moroccan specimens that were carefully examined by the collectors, a tail vestige, varying in length from 4mm to 22 mm, was detected in eight individuals (62%)”. ↩

2. 15b.

   Page 6:  “Caudal vertebrae also are vestigial in M. sylvanus (Fig. 4), and, as previously noted by Waldeyer (1896, p. 783) and Schultz (1925, pp. 249-250), these vertebrae do not extend into the external tail; for this reason, Waldeyer and Schultz have characterized the tail vestige in M. sylvanus as "soft."  The number of caudal vertebrae in this species varies from two to five (Appendix III), with a modal number of three (13 of 29 specimens reported).” ↩ ↩

Müller, Fabiola, and Ronan O'Rahilly.  “The primitive streak, the caudal eminence and related structures in staged human embryos.”  Cells Tissues Organs 177(1):2–20.  2004.  A study of the tail end of 52 human embryos at stages 8 to 23 of development, each cut into thin serial sections, with 42 of them checked by precise graphic reconstructions.  It found that the caudal eminence, a terminal cap of tissue at the very end of the embryo, makes the caudal structures but does not form even a temporary tail.  The article quotes this to show that the embryo's tail end does not form a tail, and leaves open whether the human tail is a leftover of that tip.

1. 16a.

   Section Abstract:  “The caudal region of the trunk was reassessed in 52 serially sectioned human embryos of stages 8-23”.  Section Abstract, item (7):  “The eminence produces the caudal part of the notochord and, after closure of the caudal neuropore, all caudal structures, but it does not produce even a temporary 'tail' in the human.” ↩

Schmidt, H.  “Supernumerary nipples: prevalence, size, sex and side predilection, a prospective clinical study.”  European Journal of Pediatrics 157(10):821–823.  1998.  A prospective clinical study of 502 patients that counted how many had extra nipples, and their size, sex and side.  It found 28 cases (5.6%) of a small or middle-sized extra areola or nipple, more often in males and on the left side.  The article uses the 5.6% figure to show that the trait is too common to meet the "extreme rarity" test.

1. 17a.

   Section Abstract:  “Out of 502 patients, 28 (5.6%) exhibited a supernumerary nipple of small (only areola with diameter less than 30% of normal areola) or middle size (areola with nipple, diameter 30%-50% of normal areola).”  Section Conclusion:  “A supernumerary areola or a supernumerary areola with nipple is a frequent finding.” ↩

Teplica, David et al.  “Newly identified gross human anatomy: eight paired vestigial breast mounds run along the embryological mammary line.”  Plastic and Reconstructive Surgery Global Open 9(10):e3863.  2021.  A study of 20 lean adults (10 men and 10 women), whose torsos were photographed, grid-mapped and pinch-tested at 250 standard spots for fullness under the skin.  It found paired mounds in all participants, running in curved lines from the armpit to the groin, in the exact form of milk lines.  The article cites it only for that description of the milk line and does not rely on its mound measurements.

1. 18a.

   Section Introduction:  “The presence of "ectopic nipples" or "polythelia" has been documented in both genders, and "supernumerary" structures have been reported occurring along the embryological milk line.”  “Several well-known anatomic atlases have presented illustrations that visually summarize accessory breasts along curving "milk lines" descending from axillae to proximal thighs bilaterally”.  Figure 1:  “matching the curvilinear lines of the mammary ridges seen in embryos of all placental mammals”. ↩ ↩

Wieland, Carl.  “The strange tale of the leg on the whale.”  Creation 20(3):10–13.  Jun 1998.  A magazine article by Carl Wieland of Creation Ministries International, a creationist ministry, on a reported whale with a complete hind leg.  Wieland traces the claim to a popular book by Robert Bakker, which cites a whale book by E. J. Slijper; he finds the Slijper case is a small bump of bone with no photograph.  The article uses Wieland's test: a mutation can explain an extra bone, but not an actual leg.

1. 19a.

   “A mutational defect in this program could easily cause one or more extra pieces of bone to form, which would almost inevitably be in the same region, either separate from or fused with the normal bone.  In the same way, people can be born with extra fingers, ribs, nipples, etc.” ↩

2. 19b.

   “such an explanation would be unable to cope with the occurrence in modern whales of an actual leg (internal or external), since this would clearly have design features which would never have been needed if the first whales were created.” ↩ ↩

Copcu, Eray et al.  “Cutaneous horns: are these lesions as innocent as they seem to be?”  World Journal of Surgical Oncology 2:18.  2004.  A report on eleven patients with cutaneous horns (cone-shaped growths that rise above the skin) treated at one centre between January 2000 and January 2004.  Eight of the lesions were benign, two were squamous cell carcinomas (a skin cancer) and one was a basal cell carcinoma (another skin cancer).  The article uses it for the point that a horn can grow from a benign skin lesion or from a cancerous one.

1. 20a.

   Section Abstract, Background:  “Cutaneous horns (cornu cutaneum) are uncommon lesions consisting of keratotic material resembling that of an animal horn.  Cutaneous horn may arise from a wide range of the epidermal lesions, which may be benign, premalignant or malignant.” ↩

Yu, R. C. et al.  “A histopathological study of 643 cutaneous horns.”  British Journal of Dermatology 124(5):449–452.  1991.  A review of past cases: the authors examined 643 cutaneous horns from their department between 1970 and 1989 and looked under a microscope at the tissue at the base of each one.  They found that 38.9% of the horns grew from lesions that were malignant (cancerous) or premalignant (able to turn into cancer), and 61.1% grew from benign ones.  The article uses it for how often horns come from cancer or precancer, and where those lesions sit on the body.

1. 21a.

   Section Abstract:  “A retrospective study of 643 cutaneous horns examined in our department between 1970 and 1989 revealed that 38.9% were derived from malignant or premalignant epidermal lesions, and 61.1% from benign lesions.”  “over 70% of all (pre)malignant lesions were found on the nose, pinnae, backs of hands, scalp, forearms and the face”. ↩

Tan, Üner.  “A new syndrome with quadrupedal gait, primitive speech, and severe mental retardation as a live model for human evolution.”  International Journal of Neuroscience 116(3):361–369.  2006.  A short paper by the researcher who reported the syndrome, describing five of nineteen children from one family whose parents were related by blood.  The author's own claim is that the syndrome suggests a backward stage in human evolution, so the article uses it as the source of that claim.

1. 22a.

   Section Abstract:  “This syndrome was exhibited by 5 of 19 children from a consanguineous family.  The pedigree demonstrated a typical autosomal-recessive inheritance.  The genetic nature of this syndrome suggests a backward stage in human evolution, which is most probably caused by a genetic mutation, rendering, in turn, the transition from quadrupedality to bipedality.”  “This new syndrome may be used as a live model for human evolution.” ↩

University of Texas at Austin.  “Humans walking on all fours is not backward evolution.”  ScienceDaily.  Jul 16, 2014.  A press release from the university about a 2014 study in PLOS ONE by Liza Shapiro and colleagues.  The study analyzed 518 walking strides from videos of people with this condition, including the BBC footage, and compared them with healthy adults walking on all fours in a laboratory.  It found that 98 percent of the strides were lateral sequences, unlike the diagonal sequences of apes and monkeys, and that the earlier study appeared to have confused diagonal couplets with diagonal sequences.  The article cites it for the 2006 BBC documentary that made the family famous.

1. 23a.

   “Contradicting earlier claims, "The Family That Walks on All Fours," a group of quadrupedal humans made famous by a 2006 BBC documentary, have simply adapted to their inability to walk upright and do not represent an example of backward evolution, according to new research by Liza Shapiro, an anthropologist at The University of Texas at Austin.” ↩

Ozcelik, Tayfun et al.  “Mutations in the very low-density lipoprotein receptor VLDLR cause cerebellar hypoplasia and quadrupedal locomotion in humans.”  PNAS 105(11):4232–4236.  2008.  A genetics study of four large Turkish families whose parents were related by blood.  In two of the families the team found mutations in the VLDLR gene, and in the other two the trait was not linked to chromosome 9p, where that gene lies.  The article cites it for the finding that the gene link held in only two of the four families.

1. 24a.

   Section Abstract:  “Quadrupedal gait in humans, also known as Unertan syndrome, is a rare phenotype associated with dysarthric speech, mental retardation, and varying degrees of cerebrocerebellar hypoplasia.  Four large consanguineous kindreds from Turkey manifest this phenotype.”  “In two other families (B and C), the phenotype is not linked to chromosome 9p.” ↩

2. 24b.

   Section Results, family descriptions:  “All patients had severe truncal ataxia affecting their walking patterns.” ↩

Herz, Joachim et al.  “"Devolution" of bipedality.”  PNAS 105(21):E25.  2008.  A letter to the journal, a short comment on the Ozcelik paper by three geneticists.  It argues that the quadrupedal walk is a side effect of severe balance problems (ataxia) and an unfavorable environment, not a separate genetic syndrome.  The article cites it for the Hutterite families in North America, where people with a complete deletion of the VLDLR gene walk upright.

1. 25a.

   “In contrast to the Turkish population reported by Ozcelik et al., Hutterites carrying a complete deletion of VLDLR are bipedal (3).” ↩

2. 25b.

   “Quadrupedal locomotion is more likely an adaptation to the severe truncal ataxia present in all VLDLR-deficient patients, resulting from a combination of uneven, rough surfaces in rural areas, imitation of affected siblings, and lack of supportive therapy.”  “Quadrupedal gait is thus likely an epiphenomenon caused by neurodevelopmental malformation and ataxia combined with unfavorable environmental conditions and does not define a separate genetic entity.” ↩

Humphrey, Nicholas et al.  “Genes and quadrupedal locomotion in humans.”  PNAS 105(21):E26.  2008.  A letter to the journal by three researchers, Nicholas Humphrey, Stefan Mundlos and Seval Türkmen, who also investigated a family in Iraq in which four adult siblings walk on all fours.  They argue that the walking is an adaptation to balance problems caused by underdeveloped cerebellar tissue (the part of the brain that helps control balance), and that a walker made the difference in one family.  The article cites it for the different mutations found in different families and for the walker that made the difference in family B.

1. 26a.

   “However, it turns out that the Iraqi family and three of the four Turkish families each carry a different mutation.  Moreover, in Turkish family B, one individual with the same homozygous mutation as his affected siblings is not quadrupedal”. ↩

2. 26b.

   “We see quadrupedal locomotion as an adaptive—and undoubtedly effective—compensation for problems with balance caused by congenital cerebellar hypoplasia.”  “As was proved with family B, during the making of a TV documentary, the provision of a walker could indeed make all the difference (see ref. 6).” ↩

Marsh, O. C.  “Recent polydactyle horses.”  American Journal of Science, third series 43(256):339–355.  Apr 1892.  A short journal paper by the writer, O. C. Marsh, who had discovered an extinct horse species in the Rocky Mountains.  It sorts living horses with extra toes (polydactyl horses) into types, using the writer's own examinations and specimens, photographs and descriptions sent by others.  It leaves the full discussion of atavism (a throwback to an ancestor's trait) for another occasion.  The article cites it for the conclusion that the cases the writer examined critically are best explained as atavism.

1. 27a.

   Page 345:  “In every specimen examined, where the carpal or tarsal series of bones were preserved, and open to inspection, the extra digits were supported in the usual manner.”  “It is noteworthy that none of the extra toes examined represents the fifth digit, although the reappearance of this rather than the first might naturally be looked for.” ↩

2. 27b.

   Page 351:  “All the examples of polydactylism in the horse which the writer has had opportunity to examine critically are best explained by atavism, and many of them admit no other solution.” ↩

Kavanagh, Kathryn D. et al.  “Evidence of five digits in embryonic horses and developmental stabilization of tetrapod digit number.”  Proceedings of the Royal Society B 287(1920):20192756.  2020.  A research paper in which the authors examined limbs from horse embryos estimated at 29 to 35 days post coitus (dpc), cut them into serial thin sections, stained them and counted the digit condensations (the first cartilage that will become each digit).  They found five digit condensations in the early embryos, and the two flanking splint bones of the adult horse arise from fusions of digits I and II and of digits IV and V.  The article cites it for the 2020 finding that early horse embryos have five digits.

1. 28a.

   Section Abstract:  “Here we show that early Equus embryos go through a stage with five digit condensations, and that the flanking splint metapodials result from fusions of the two anterior digits I and II and the two posterior digits IV and V, in a striking parallel between ontogeny and phylogeny.” ↩

Holt, Rebekah L.  “What about horse toe evolution?”  creation.com.  Jun 24, 2008.  A creationist web article, arguing from the view that God created each kind of living thing (here the "equine kind").  It argues that the splint bones and other parts called vestigial (leftover) are useful, and that extra-toed horses show only extra-long splint bones on a horse of the equine kind, which do not prove Darwin's theory of a transitional creature.  The article cites it for the creationist reply to the extra-toed horse cases.

1. 29a.

   Section Splint bones:  “It only illustrates that a totally equine skeleton had extra long splint bones supporting its fossilized leg that at one time supported a member of the equine kind.  The modern equine's regressing splints suggest only that the genetic material for extended splints has been lost.” ↩

Andrews, Roy Chapman.  “A remarkable case of external hind limbs in a humpback whale.”  American Museum Novitates 9:1–6.  Jun 3, 1921.  A short paper in the American Museum Novitates series.  It describes a female humpback whale taken in July 1919 with two protrusions on its underside, and examines the two bones and two cartilages that the Provincial Museum in Victoria, British Columbia, made available for study.  The article cites it for the 1919 capture, the identification of the bones, the conclusion that they were vestigial hind limbs, and the statement that no other such case had been reported among hundreds of thousands of whales killed.

1. 30a.

   Page 1:  “In July 1919, a female Humpback Whale (Megaptera nodosa) with two remarkable protrusions on the ventral side of the body, posteriorly, was captured by a ship operating from the whaling station at Kyuquot, on the west coast of Vancouver Island, British Columbia.” ↩

2. 30b.

   Page 2:  “The skeletal remains in my possession consist of two bones and two heavy cartilages.  When placed in position as in Fig. 2, the total length is 31 inches.”  Page 4:  The bones are identified under the headings FEMUR (cartilage), TIBIA (bone), TARSUS (cartilage) and METATARSAL (bone). ↩

3. 30c.

   Page 2:  “I have come to the conclusion that the protrusions actually do represent vestigial hind limbs and show a remarkable reversion to the primitive quadripedal condition.” ↩

4. 30d.

   Page 6:  “Although hundreds of thousands of whales have been killed, especially in the last fifty years since the beginning of shore-whaling, no other instance has been reported.” ↩

Ogawa, Teizo, and Toshiro Kamiya.  “A case of the cachalot with protruded rudimentary hind limbs.”  Scientific Reports of the Whales Research Institute 12:197–208.  1957.  A report by two Japanese anatomists on a female sperm whale (cachalot) caught off Japan in 1956 that had two protrusions beside its genital opening.  They cut out the skin over the protrusions, studied X-ray photographs of the left one, found a pelvic bone 19.5 cm long inside it, and concluded that the bumps were very probably an atavism.  The article cites this as the verdict on a second whale, a sperm whale, set beside Andrews' humpback.

1. 31a.

   Page 207:  “This case can be understood by assuming abnormal retention of the early embryonic state, and show very probably an atavism back to the quadripedal condition of the whales' remote ancestors.  It can never be a malformation of no phylogenetic significance.” ↩

Thewissen, J. G. M. et al.  “Developmental basis for hind-limb loss in dolphins and origin of the cetacean bodyplan.”  PNAS 103(22):8414–8418.  2006.  A research paper that studied gene activity in embryos of the pantropical spotted dolphin (Stenella attenuata).  The authors found that the dolphin's hind-limb bud forms, then stops growing around the fifth gestational week, and that the gene Shh (sonic hedgehog), which tells a limb where to grow, is missing from it, along with its upstream switch Hand2.  The article uses it to show that dolphin embryos start a hind-limb bud, and that the genes that build the limb are not switched on in it.

1. 32a.

   Section Abstract:  “cetacean embryos do initiate hind-limb bud development.  In dolphins, the bud arrests and degenerates around the fifth gestational week”.  “We find that failure to establish a ZPA is associated with the absence of Hand2, an upstream regulator of Shh.” ↩ ↩

Ohsumi, Seiji.  “A dolphin (Stenella caeruleoalba) with protruded rudimentary hind limbs.”  Scientific Reports of the Whales Research Institute 19:135–136.  1965.  A short report on one male blue-white dolphin (Stenella caeruleoalba), 230 cm long, with two protruding rudimentary hind limbs.  It was caught in a herd of about 450 at Kawana Beach, Japan, in December 1963, and the author measured its body and limbs.  The article cites it for how rare such a dolphin is, using the author's own statement that his group had found one only after about ten thousand of the species had been studied by Nishiwaki's group.

1. 33a.

   Page 135:  “Dr. Nishiwaki and his group have investigated this species of dolphin on about ten thousand individuals, but it is the first time for us to find such an individual.” ↩

Wise, Kurt P.  “Towards a creationist understanding of 'transitional forms'.”  CEN Technical Journal 9(2):216–222.  1995.  An overview essay by Kurt P. Wise, a young-age creationist palaeontologist who helped develop baraminology, the creationist classification system.  It argues that creationists should not spend scarce time on the transitional-fossil question, and it treats the early whale fossils as one of the hardest cases for creationists.  The article cites it for Wise's answer to the whale with hind limbs: that living whales carry latent genetic information for small hind limbs, perhaps from Basilosaurus in a created kind.

1. 34a.

   Page 220:  “This suggests that modern cetaceans have latent genetic information for the development of small hind limbs.  Could this mean that Basilosaurus, for example, (which has hind limbs and pelvis) is actually an early post-Flood representative of some cetacean baramin”. ↩

Wieland, Carl.  “A dolphin with legs—NOT.”  creation.com.  Nov 6, 2006.  A popular article on the creation.com website by Carl Wieland, published 6 November 2006, about press reports of a bottlenose dolphin found at Taiji, Japan, with a pair of rear fins.  Wieland argues that the rear fins are a loss of genetic information, not a step in evolution, and that dolphins with two fins may still carry the information for four.  The article cites it because Wieland applies Kurt Wise's latent-information answer to dolphins.

1. 35a.

   “Today's two-finned dolphins may actually have the latent genetic information for generating all four fins.  All dolphins may have once had two rear fins, and subsequently lost the information for generating them.” ↩

Galis, Frietson et al.  “Why five fingers? Evolutionary constraints on digit numbers.”  Trends in Ecology and Evolution 16(11):637–646.  2001.  A review article on why evolution has not regained extra limb digits once they were lost; the authors write that an evolutionary reversal of limb reduction has never occurred.  They argue that extra digits have side effects on other body parts, so mutations for them are usually selected against.  The article cites it for the authors' description of a St Bernard's extra toe as an atavistic first digit, a return to an ancestral form.

1. 36a.

   On report page 2, in the caption to Fig. 1.  “(b) Foot of St Bernard dog with five toes, including an atavistic first digit (arrow).  In wolves and most other canids, the first toe is reduced, and they only have four toes.” ↩

Park, Kyoungtag et al.  “Canine polydactyl mutations with heterogeneous origin in the conserved intronic sequence of LMBR1.”  Genetics 179(4):2163–2172.  2008.  A research paper from two Korean universities that traced an extra hind toe in dogs to the gene LMBR1.  The team used family studies of a Korean dog breed, population data from Western breeds, and tests of the mutated DNA in transgenic mice, and it found two separate mutations, DC-1 and DC-2, that go with the trait.  The article cites it for the clean single-gene inheritance of the trait, and for the authors' point that the extra toe restores the first digit lost during canine evolution.

1. 37a.

   Section Discussion, paragraph 4:  “In fact, even in Great Pyrenees, the association with Alx4Δ51 alleles is genetically ambiguous, whereas DC-1 or DC-2 associations are clearly Mendelian with an autosomal-dominant mode of inheritance.” ↩

Kollar, Edward J., and Christopher Fisher.  “Tooth induction in chick epithelium: expression of quiescent genes for enamel synthesis.”  Science 207(4434):993–995.  1980.  A laboratory experiment that combined chick epithelium, the outer tissue layer, with mouse molar mesenchyme, the underlying tissue that shapes a tooth, and grafted the pair inside the eye.  The authors report complete tooth crowns with cells that make enamel, and they say the results suggest that birds lost teeth through a change in tissue signals rather than by losing the enamel genes.  The article cites it as the laboratory result that birds still carry the genes for enamel, a claim later biologists questioned.

1. 38a.

   Section Abstract:  “Intraocular grafts of chick epithelium combined with mouse molar mesenchyme produced a variety of dental structures including perfectly formed crowns with differentiated ameloblasts depositing enamel matrix.  The results suggest that the loss of teeth in Aves did not result from a loss of genetic coding for enamel synthesis in the oral epithelium but from an alteration in the tissue interactions requisite for odontogenesis.” ↩

Marshall, Charles R. et al.  “Dollo's law and the death and resurrection of genes.”  PNAS 91(25):12283–12287.  1994.  A research paper on Dollo's law, the idea that evolution does not substantively reverse, which uses data on how much protein-coding genes tolerate change to estimate how long a silenced gene or developmental program can stay revivable.  It finds that revival is plausible over 0.5 to 6 million years, but not after more than 10 million years unless the gene keeps another function, and it judges the hen's teeth claim most likely an experimental artifact.  The article uses this time limit to test the loss of teeth in birds and the loss of legs in whales.

1. 39a.

   Section Abstract:  “we show that, in fact, there is a significant probability over evolutionary time scales of 0.5-6 million years for successful reactivation of silenced genes or "lost" developmental programs.  Conversely, the reactivation of long (> 10 million years)-unexpressed genes and dormant developmental pathways is not possible unless function is maintained by other selective constraints; the classic example of the resurrection of "hen's teeth" is most likely an experimental artifact, and the experimental reactivation of the Archaeopteryx limb developmental program has been shown to be a misinterpretation.” ↩ ↩

Meredith, Robert W. et al.  “Evidence for a single loss of mineralized teeth in the common avian ancestor.”  Science 346(6215):1254390.  2014.  A genome comparison across nearly all living bird orders that looked for broken copies of the genes used to make the enamel and dentin of teeth in other vertebrates.  The authors found shared broken genes, which indicate that the common ancestor of modern birds lacked mineralized teeth, and they estimate that this loss happened about 116 million years ago.  The article cites it for that date of about 116 million years ago for the loss of bird teeth.

1. 40a.

   Section Abstract:  “We performed comparative genomic analyses representing lineages of nearly all extant bird orders and recovered shared, inactivating mutations within genes expressed in both the enamel and dentin of teeth of other vertebrate species, indicating that the common ancestor of modern birds lacked mineralized teeth.  We estimate that tooth loss, or at least the loss of enamel caps that provide the outer layer of mineralized teeth, occurred about 116 million years ago.” ↩ ↩

Chen, YiPing et al.  “Conservation of early odontogenic signaling pathways in Aves.”  PNAS 97(18):10044–10049.  2000.  A laboratory study of chick embryos that checked whether the genes known to start tooth development in mice are switched on in the chick jaw.  The authors found the early genes Fgf8, Pitx2, Barx1 and Pax9 active, but Bmp4, Msx1 and Msx2 absent, and they suggest that the missing Bmp4 may explain why living birds stop tooth development early.  The article cites it for the finding that the early tooth signals remain in the chick jaw and can still be switched on.

1. 41a.

   Section Abstract:  “Similar to the mouse dental lamina, expression of Fgf8, Pitx2, Barx1, and Pax9 defines a potential chick odontogenic region.  However, the expression of three molecules involved in tooth initiation, Bmp4, Msx1, and Msx2, are absent from the presumptive chick dental lamina.”  “These results show that, although latent, the early signaling pathways involved in odontogenesis remain inducible in Aves and suggest that loss of odontogenic Bmp4 expression may be responsible for the early arrest of tooth development in living birds.” ↩ ↩

Harris, Matthew P. et al.  “The development of archosaurian first-generation teeth in a chicken mutant.”  Current Biology 16(4):371–377.  2006.  A research paper on the talpid2 chicken mutant, whose embryos form teeth.  The authors compared its tooth formation with that of an alligator and found teeth of the crocodile type forming in a bird embryo.  The article cites it as the better case of teeth returning in a bird, and the authors' model for how birds lost teeth is that a signaling center moved while the tissue kept the ability to form teeth.

1. 42a.

   Section Abstract:  “We compare the formation of teeth in the talpid2 mutant with that in the alligator and show the formation of decidedly archosaurian (crocodilian) first-generation teeth in an avian embryo.” ↩

2. 42b.

   Section Abstract:  “We propose an epigenetic model of the developmental modification of dentition in avian evolution; in this model, changes in the relative position of a lateral signaling center over competent odontogenic mesenchyme led to loss of teeth in avians while maintaining tooth developmental potential.” ↩

Biello, David.  “Mutant Chicken Grows Alligatorlike Teeth.”  Scientific American.  Feb 22, 2006.  A news report by David Biello, a contributing editor at Scientific American, on the Harris study of the talpid2 chicken mutant.  It explains that the mutant embryos form tooth-like structures, and that a virus copying the mutation's signals made normal chickens grow teeth briefly, which were then reabsorbed.  The article cites it for the lethal nature of the trait and for that virus experiment in normal embryos.

1. 43a.

   “This trait is lethal, meaning that such mutants are never born, but some incubate in eggs as long as 18 days.” ↩

2. 43b.

   “"They don't make a molar," explains development biologist John Fallon, who oversaw Harris's work.  "What they make is this conical, saber-shaped structure that is clearly a tooth.  The other animal that has a tooth like that is an alligator."” ↩

3. 43c.

   “Harris proved this by engineering a virus to mimic the molecular signals of the mutation and caused normal chickens to briefly develop teeth that were then reabsorbed into the beak.” ↩

Wieland, Carl.  “Chickens with teeth.”  creation.com.  Creation Ministries International.  Jul 24, 2006.  A web commentary by Carl Wieland of Creation Ministries International on a 2006 study in Current Biology of a chicken mutant with tooth-like structures in its beak.  Wieland argues that the teeth come from genetic information already present in the created kind, not from a new evolutionary gain.  The article uses it as the creationist reply to that study, and the reply accepts that the teeth come from genes that were switched off.

1. 44a.

   “The authors reported that a mutant chicken turns out to have had tooth-like structures in its beak.  It also had serious limb defects and died shortly after it was hatched.” ↩

2. 44b.

   Section What does it show?:  “Stripped of evolutionary assumptions, it shows that the gene pool of the chicken's created kind included the capacity to generate teeth.” ↩

3. 44c.

   Section What does it show?:  Wieland quotes CMI's own 1999 Creation magazine item.  “the loss or "switching off" of genes expressing the development of a tooth, like the "loss" of wings in some birds, or of eyes on fish in caves, is not an indication of how the information for such structures arose by natural means.  "Devolution" would be a better term.” ↩

4. 44d.

   Section What does it show?:  “But in reality, toothed birds in the fossil record also have the same type of teeth, which fits creationist expectations just as well.” ↩

Gish, Duane T.  “Evolution and the Human Tail.”  Impact.  Institute for Creation Research.  Mar 1, 1983.  A short reply by Duane Gish, vice president of the Institute for Creation Research, in the institute's Impact publication, to a 1982 case report by Fred D. Ledley, 'Evolution and the human tail: a case report,' New England Journal of Medicine 306(20):1212–1215.  Gish quotes Ledley's own words that the appendage had no vertebrae and was not at the end of the spine, and argues from them that it was not a tail.  The article uses it for that answer, and notes that Gish's claim that inherited tails have 'never been known to occur' goes beyond the evidence.

1. 45a.

   Page 1213:  Gish is quoting Ledley's 1982 article here.  “When the caudal appendage is critically examined, however, it is evident that there are major morphologic differences between the caudal appendage and the tails of other vertebrates.  First of all, the caudal appendage does not contain even rudimentary vertebral structures.… Secondly, the appendage is not located at the caudal terminus of the vertebral column.  It is possible that this structure is merely a dermal appendage coincidentally located in the caudal region.  This possibility cannot be excluded.” ↩

2. 45b.

   Section Case Description:  Describes Ledley's patient.  “It was located adjacent to the sacrum and was offset from the mid-line about 1/2 inch.  The appendage had a soft fibrous fatty core and was covered with skin of normal texture.” ↩

3. 45c.

   Section Alternative Explanations:  “If this caudal appendage were due to a mutation, the mutant gene would be passed on to offspring and would eventually be reexpressed in some of those offspring.  This has never been known to occur.  The anomaly is thus not due to a mutation but to some disarrangement that occurred during embryological development.” ↩

Menton, David N.  “The Human Tail and Other Tales of Evolution.”  answersingenesis.org.  Answers in Genesis.  Jul 29, 2017.  An essay by David N. Menton, first published in St. Louis MetroVoice 4(1) in January 1994, later featured in Essays on Origins: Creation vs. Evolution and republished by Answers in Genesis in 2017.  It answers Fred Ledley's 1982 case report of a baby with a 'human tail' by arguing that the growth was a fatty outgrowth of skin and not a tail.  The article uses it for the claim that no human appendage has any tail features, and disputes that claim where muscle is concerned.

1. 46a.

   “All true tails have bones in them that are a posterior extension of the vertebral column.  Also, all true tails have muscles associated with their vertebrae, which permit some movement of the tail.  Ledley conceded that there has never been a single documented case of an animal tail lacking these distinctive features, nor has there been a single case of a human caudal appendage having any of these features.” ↩

DeWitt, David A.  “Setting the Record Straight on Vestigial Organs.”  answersingenesis.org.  Answers in Genesis.  May 28, 2008.  A 2008 Answers in Genesis essay by David A. DeWitt that answers Laura Spinney's New Scientist article 'Five Things Humans No Longer Need', which lists five human organs as vestigial.  DeWitt goes through each organ and argues that the coccyx has a function, and that the 'tails' some babies are born with are fatty tumors.  The article uses it for the claim that these growths have no bones or muscles, and disputes that claim on muscle.

1. 47a.

   Section The Tailbone:  “But these so called tails are not really tails at all and instead are a type of fatty tumor.  There are no bones or muscles in them at all, and thus, it cannot truly be considered a vestigial organ.” ↩

Egnor, Michael.  “The Myth of Human "Tails": A Physician and Surgeon's Perspective.”  Evolution News (now Science and Culture Today).  May 23, 2014.  A 2014 reply by Michael Egnor, a professor of neurosurgery and pediatrics at Stony Brook who argues for intelligent design, to Karl Giberson's reference to human 'tails', which Egnor calls junk science.  Egnor says he has operated on at least five such children, and that their appendages are congenital lesions, usually a sinus tract linked to a fatty lump at the base of the spine, with the spinal cord tethered in over 50% of cases.  The article calls it the best-informed reply on the design side, and notes that it concedes the muscle that Menton and DeWitt deny.

1. 48a.

   “I have operated on quite a few children (at least five) with what Giberson, a physicist, would call a "tail."”  “The appendage many contain regions of primitive muscle, fat, nerves, blood vessels, etc., but not vertebrae.”  The page prints "many" for "may". ↩

2. 48b.

   “A child with a sacral appendage is no more a reversion to an animal with a tail than a child with phocomelia is a reversion to a seal or a child with severe holoprosencephaly (which can be associated with a single midline eye) is a reversion to the mythical Cyclops.” ↩

Smith, Calvin, and Carl Wieland.  “Human tails? 'Atavistic tails' and evolution.”  creation.com.  Creation Ministries International.  Feb 20, 2015.  A Creation Ministries International article by Calvin Smith and Carl Wieland, published 20 February 2015 and updated 30 April 2015, that draws on medical papers about human 'tails'.  It argues that these growths are birth defects, not throwbacks to an animal ancestor, and that the terms 'true tail' and 'pseudo tail' are misleading.  The article uses it for its account of the anatomy and for its claim that doctors agree these are birth defects, which it says overstates the case.

1. 49a.

   Section What are these 'tails'?:  “In medical literature some are referred to as 'true tails' (which contain muscle, can move and are located extending from the coccyx) and others are termed 'pseudo tails' (which are generally flaccid and can be located in a variety of places).  This terminology itself (based on evolutionary assumptions) is one of the challenges for creationists arguing against evolutionists about this claim.” ↩

2. 49b.

   Section Harmless leftovers?:  “Modern doctors familiar with this sort of condition seem unanimous in their description of human tails as being the result of birth defects.” ↩

Luskin, Casey.  “Human tails.”  discovery.org.  Discovery Institute.  May 22, 2014.  A 2014 series by Casey Luskin of the Discovery Institute, collected as one article, that replies to the physicist Karl Giberson's statement of the Darwinian view of human 'tails'.  It discusses a 1998 study by Lu and colleagues in Pediatric Neurology, which links human tails to spinal dysraphism and other developmental problems.  Luskin argues for intelligent design and is not a young-earth creationist.  The article uses it because its claim that no human tail has vertebrae is followed by a case report, which Luskin himself quotes, that calls a pseudotail a prolongation of the coccygeal vertebra.

1. 50a.

   “In other words, if humans have a bony tail, it's not a "true tail" — it's a "pseudotail" because of other abnormalities, but if it's a "true tail, it contains no bone, cartilage, notochord, or spinal cord.  And no human tail contains vertebrae.” ↩

2. 50b.

   “But what about "pseudotails" — can't they contain bone?  Yes, sometimes they can, but pseudotails don't contain vertebrae (as all other mammalian tails do)”.  The next paragraph quotes a case report:  “The pseudotail is an anomalous prolongation of the coccygeal vertebra, lipoma, teratoma, chondrodystrophy, or parasitic fetus.” ↩