Male Nipples

Gould, Stephen Jay.  “Male Nipples and Clitoral Ripples.”  Bully for Brontosaurus: Reflections in Natural History, 124–138.  W. W. Norton, New York.  1991.  An essay that first appeared in the magazine Natural History under the magazine's title "Freudian Slip," and was reprinted in this 1991 collection.  Gould argues that male nipples need no adaptive explanation, because they come from the same embryonic pathway as the female breast.  The article cites it as the classic modern treatment, which does not call male nipples bad design.

1. 1a.

   Page 124:  In a footnote on this page, Gould writes:  “Natural History magazine, published by a group of fine but slightly overcautious folks, first brought out this essay under their imposed title: "Freudian Slip." Not terrible; but not really descriptive either.” ↩

2. 1b.

   Page 125:  Erasmus Darwin's Zoonomia is quoted here through Gould, not from the 1794 original.  “In this long section, Erasmus considers only one potential exception to the principle of pervasive utility: "the breasts and teats of all male quadrupeds, to which no use can be now assigned."” ↩

3. 1c.

   Page 126:  “I have been fascinated (and, I confess, surprised) over the years to discover that no single item has evoked more puzzlement than the very issue that Erasmus Darwin chose as a primary challenge to his concept of pervasive utility— male nipples. I have received more than a dozen requests to explain how evolution could possibly produce such a useless structure.” ↩

4. 1d.

   Page 127:  “I do not doubt that the large size and sensitivity of the female breast should count as an adaptation in mammals, but the smaller male version needs no adaptive explanation at all. Males and females are not separate entities, shaped independently by natural selection. Both sexes are variants upon a single ground plan, elaborated in later embryology. Male mammals have nipples because females need them — and the embryonic pathway to their development builds precursors in all mammalian fetuses, enlarging the breasts later in females but leaving them small (and without evident function) in males.” ↩ ↩ ↩

5. 1e.

   Page 128:  “In my view of life, akin to Davis's concept of constraint and integration, male nipples are an expectation based on pathways of sexual differentiation in mammalian embryology.” ↩

Darwin, Charles.  On the Origin of Species by Means of Natural Selection.  John Murray, London.  1st edition.  1859.  The first edition of Darwin's book on how species arose by natural selection, published on 24 November 1859.  The article quotes its section on rudimentary organs, where Darwin treats male nipples as a leftover part that is evidence of descent from earlier forms.

1. 2a.

   Page 450:  “Organs or parts in this strange condition, bearing the stamp of inutility, are extremely common throughout nature.  For instance, rudimentary mammæ are very general in the males of mammals”. ↩ ↩

Shermer, Michael et al.  “These Truths Are Not Self-Evident.”  Scientific American 315(5):46–53.  Nov 2016.  A 2016 magazine feature in which five writers each defend a settled scientific finding: evolution, homeopathy, climate change, vaccines and alien visits.  It was printed under the title "5 Things We Know To Be True."  The article cites it as a popular 2016 list of "useless vestigial structures" that includes male nipples.

1. 3a.

   Section Evolution is the only reasonable explanation for the diversity of life on earth:  “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.” ↩ ↩

Coyne, Jerry A.  “Musings on Why Evolution is True (the book).”  Why Evolution Is True (blog).  Jul 19, 2024.  A blog post by Coyne about his book Why Evolution Is True.  The article cites it as his 2024 statement that male nipples are a feature a designer could have made better.

1. 4a.

   “And I haven't yet heard of an adaptive explanation for nipples in human males, our wisdom teeth, the developmental sequence of our kidney, or our transitory coat of hair in utero (the "lanugo"), but I'm sure that if you look hard enough on the Internet, you'll find IDers and creationists showing how these aren't really "senseless signs of history", but are actually adaptive.”  Later in the same paragraph, Coyne writes ("featurs" is his spelling):  “featurs that, if there was a god or a Designer, could have been designed better”. ↩ ↩

Moore, Keith L.  The Developing Human: Clinically Oriented Embryology.  Dar Al-Qiblah, Jeddah.  3rd edition.  1983.  A clinical textbook of human embryology by Keith L. Moore, a professor of anatomy at the University of Toronto, whose third edition came from W. B. Saunders in 1982.  This 1983 edition reprinted it with Islamic additions by Abdul-Majeed Azzindani, which the article does not use.  The article uses its dates for the early stages of the breast and of the sex organs.

1. 5a.

   Page 437, figures 20-6:  The caption reads:  “Ventral view of an embryo during stage 13 (about 28 days), showing the mammary ridges.”  The text reads:  “These epithelial ridges appear during the fourth week, but disappear in humans except in the pectoral area.” ↩ ↩

2. 5b.

   Page 436:  “The mammary glands first begin to develop during the sixth week as solid downgrowths of the epidermis that extend into the underlying mesenchyme (Fig. 20-6C).” ↩ ↩

3. 5c.

   Page 437:  “The nipple forms during the perinatal period as the result of proliferation of mesenchyme underlying the areola, a circular area of skin around the nipple. The nipples are poorly formed and often depressed in newborn infants.” ↩ ↩

4. 5d.

   Page 437:  “The mammary glands in males normally undergo little postnatal development. Estrogen given to males tends to make their rudimentary mammary glands develop into the feminine type.” ↩

5. 5e.

   Page 271:  “Although the genetic sex of an embryo is determined at fertilization by the kind of sperm that fertilizes the ovum (see Chapter 2), there is no morphological indication of sex until the seventh week, when the gonads (future ovaries or testes) begin to acquire sexual characteristics.”  Page 274:  “Before the seventh week of embryonic life, the gonads of both sexes are identical in appearance and are referred to as indifferent gonads”. ↩ ↩

6. 5f.

   Page 281:  “Distinguishing sexual characteristics begin to appear during the ninth week, but the external genital organs are not fully formed until the twelfth week.” ↩

Zheng, Zhengui et al.  “Developmental basis of male nipple loss and retention in mammals.”  Research Square.  Oct 24, 2025.  A research preprint, version 1, that compares nipple development in male and female mice with guinea pigs, which keep their nipples.  It has not yet been peer reviewed by a journal, and its groups are small, three or four animals each.  The article uses it for the finding that deleting the androgen receptor in the tissue around the mammary bud gives male mice nipples.

1. 6a.

   Section Discussion:  In the quotation, T is testosterone and MG is mammary gland; the numbers are the preprint's reference markers.  “In human fetuses, T production is initiated at approximately 8 weeks of gestation, and the maximal T content in fetal testes is achieved between 10 and 15 weeks of fetal life 58 . The MG development in human fetuses starts around gestation day 28 and the nipple buds can be seen at the end of first trimester 6 .” ↩ ↩

2. 6b.

   Figure 3:  The legend reads:  “Note that male mice developed nipples after AR deletion in mammary mesenchyme (f, n=3), but no effect was observed after AR deletion from epithelium (h, n=4).”  Section Discussion:  “our results confirmed that only mesenchymal AR causes MG atrophy and nipple loss in male mice”. ↩ ↩ ↩

3. 6c.

   Section Abstract:  “This study compared mammary gland development and hormonal regulation between guinea pigs and mice and found that androgen receptor (AR) is exclusively present in the developing mammary glands of mice during sexual differentiation.” ↩

4. 6d.

   Section Introduction:  “Males of only a few species, such as rat ( Rattus norvegicus ), mouse ( Mus musculus ) and horse ( Equus caballus ) don't have nipples 3 – 5 .”  Section Results:  “Interestingly, only in several species, such as male mice and rats, does the MG atrophy during genital sexual differentiation.” ↩

5. 6e.

   Section Discussion:  “In addition, there is no evidence that AR and ERα mRNA and protein exist in developing MGs of human fetuses.” ↩

6. 6f.

   Section Discussion:  “Most male mammals possess nipples, with only a few species losing them during fetal development. In other words, the presence of nipples in male mammals is the evolutionary norm, while the loss of nipples during embryonic development in a few male species is the exception.” ↩

7. 6g.

   Section Results:  “At later stages, the MGs continue development in females but undergo atrophy in males after E15.5.” ↩

8. 6h.

   Section Introduction:  “Except for fruit bats, MGs of most male mammals do not perform lactation, and the majority of male mammals don't have fully developed and functional MGs, but they do have nipples 1 , 2 .”  Reference 2 is Francis and others, "Lactation in male fruit bats," Nature 367:691–692, 1994. ↩

Kratochwil, K., and P. Schwartz.  “Tissue interaction in androgen response of embryonic mammary rudiment of mouse: identification of target tissue for testosterone.”  Proceedings of the National Academy of Sciences 73(11):4041–4044.  1976.  A laboratory experiment on mouse embryos that combined the gland's own cells (epithelium) with the surrounding tissue (mesenchyme), taken from normal and androgen-insensitive embryos, to see which tissue responded to testosterone.  Androgen-insensitive epithelium with normal mesenchyme responded, but normal epithelium with androgen-insensitive mesenchyme never did.  The article uses it to show that in male mice testosterone acts on the tissue around the mammary bud and destroys the bud.

1. 7a.

   Section Abstract:  “It is therefore concluded that only the mesenchyme of the mammary rudiment is the target tissue for testosterone, and that all changes in the gland epithelium, including its necrosis, are secondarily caused by testosterone-activated mesenchymal cells.” ↩ ↩

Hughes, Katherine.  “Development and Pathology of the Equine Mammary Gland.”  Journal of Mammary Gland Biology and Neoplasia 26(2):121–134.  2021.  A review of the horse udder that covers its anatomy, development, milk and disease, written by a veterinary researcher at the University of Cambridge.  It sums up published work rather than new experiments.  The article uses its anatomy section, which says the majority of male horses lack teats while some male donkeys and mules have teats on the sheath.

1. 8a.

   Section Gross Anatomy of the Mammary Gland:  “In contrast to male ruminants that have rudimentary mammary structures, the majority of male horses lack teats [ 11 ]. However, some male donkeys have teats on their sheath [ 12 ] and this is also the case in some mules (A. Mclean, personal communication) [ 11 ].” ↩ ↩

Tyndale-Biscoe, Hugh, and Marilyn Renfree.  Reproductive Physiology of Marsupials.  Cambridge University Press.  1987.  A book on the reproductive biology of marsupials, the pouched mammals.  The article uses it for what the authors say about when marsupial teats form and how the pouch and scrotum develop in unusual sex-chromosome cases.

1. 9a.

   Page 344:  “In all marsupials the teat anlagen are formed in genetically female young a few days after birth. Rarely they may form in males of some species, such as Didelphis, Monodelphis and Trichosurus illustrated by Bresslau (1912). The teats do not differentiate from a mammary line, as in Eutheria, but each begins as a separate anlage”. ↩ ↩

2. 9b.

   Page 122:  “In all except two of the intersexual marsupials referred to earlier in this Chapter (Fig. 3.2) each possessed either a pouch and mammary glands or a scrotum, and the structures were in most cases concordant with the sex-chromosome constitution.”  “If the pouch and scrotum are determined before gonadal function has been established and are not susceptible to steriod hormones thereafter, this suggests that the differentiation of the anlagen in the first few days after birth is genetically determined”.  "steriod" is the book's spelling.  The two exceptions were a Tasmanian devil and a tammar wallaby with half a pouch and half a scrotum. ↩

Griffiths, Mervyn.  The Biology of the Monotremes.  Academic Press, New York.  1978.  A book on the biology of the monotremes.  The article uses it for what Griffiths reports on nipples, areolae and mammary glands in the platypus and the echidna, in both sexes.

1. 10a.

   Page 6:  Griffiths quotes Home's 1802 report.  “Home (1802a) found "There is no appearance, that could be detected of nipples; although the skin on the belly of the female was examined with the utmost accuracy for that purpose."” ↩ ↩

2. 10b.

   Page 7:  “Apart from the fact that the areola is covered by fur* its structure is remarkably like that of the human nipple and areola.” ↩ ↩

3. 10c.

   Page 9:  “There have been reports of the presence of mammary glands in male platypuses but I have never been able to detect them.” ↩

4. 10d.

   Page 27:  “Tachyglossus males have mammary glands and areolae and it has been stated (Westling, 1889; Jacobson, 1961; Sharman, 1962) that they are as well developed as those of females. The facts are that at all seasons of the year the lobules are minute and hard to detect (Fig. 92A) but often a large fat pad is associated with them”. ↩ ↩

5. 10e.

   Page 28:  “Actually the mammary glands in male echidnas are small relative to those of females, as the mammary glands of men are relative to those of women.” ↩ ↩

6. 10f.

   Page 274:  “Mammary growth was also induced in the males by implantation of the ovarian hormones* but surprisingly the effects were far more marked than those seen in the females.” ↩

Clarke, A. et al.  “Clinical aspects of X-linked hypohidrotic ectodermal dysplasia.”  Archives of Disease in Childhood 62(10):989–996.  1987.  A clinical survey of boys with X-linked hypohidrotic ectodermal dysplasia, a disorder in which sweat glands are absent or reduced, and of their families, begun in 1985.  Letters to doctors led to contact with 56 families, and the team visited homes to examine the boys and possible carrier women.  The article uses its nipple figure, which counts absent nipples alongside simple and accessory ones.

1. 11a.

   Page 990:  “The boys had sparse scalp and body hair, only a few teeth which were peg shaped (figs 2 and 3), and diminished or absent eccrine sweat pores. The mean number of erupted teeth of the deciduous and permanent dentitions in the male subjects was six. Over 30% had abnormalities of the breasts (absent, simple, or accessory nipples)”. ↩ ↩

2. 11b.

   Page 995:  “They may require water to drink with meals and need artificial tears because of inadequate salivary and lachrymal secretion.” ↩

Wohlfart, Sigrun et al.  “Natural history of X-linked hypohidrotic ectodermal dysplasia: a 5-year follow-up study.”  Orphanet Journal of Rare Diseases 15:7.  2020.  A five-year follow-up of 25 children with genetically confirmed X-linked hypohidrotic ectodermal dysplasia, 19 boys and 6 girls aged 11 to 35 months when they joined, tracked through parent questionnaires, medical records and yearly examinations.  Its main finding is that several organs are affected early in childhood.  The article uses its table of nipple findings, where 5 of 19 boys had extra nipples or nipples of different size.

1. 12a.

   Table 3:  “Supernumerary nipple and/or nipples of different size”.  Male subjects "5 (26)", female subjects "0 (0)".  There were 19 boys and 6 girls, and the table has no row for absent nipples. ↩ ↩

van Bokhoven, Hans et al.  “Limb mammary syndrome: a new genetic disorder with mammary hypoplasia, ectrodactyly, and other hand/foot anomalies maps to human chromosome 3q27.”  American Journal of Human Genetics 64(2):538–546.  1999.  A genetics paper that describes a large Dutch family with severe hand or foot defects and underdeveloped mammary glands and nipples, and places the gene on chromosome 3q27 by linkage analysis.  The article uses it for the nipple finding, which the paper calls the most consistent defect of the syndrome.

1. 13a.

   Page 538:  Abstract:  “We report on a large Dutch family with a syndrome characterized by severe hand and/or foot anomalies, and hypoplasia/aplasia of the mammary gland and nipple. Less frequent findings include lacrimal-duct atresia, nail dysplasia, hypohydrosis, hypodontia, and cleft palate with or without bifid uvula.” ↩

2. 13b.

   Page 540:  “The most consistent defect was nipple hypoplasia/aplasia, which was seen in all affected individuals examined. Hand and/or foot anomalies and hypoplasia/aplasia of the mammary gland were also common features.”  The figure legends on pages 540–541 describe syndactyly of several fingers and toes. ↩ ↩

Marneros, Alexander G. et al.  “Mutations in KCTD1 cause scalp-ear-nipple syndrome.”  American Journal of Human Genetics 92(4):621–626.  2013.  A genetics paper that finds mutations in the KCTD1 gene in people with scalp-ear-nipple syndrome, which causes missing scalp skin, breast defects and ear anomalies.  Its introduction describes the breast defects as ranging from small or missing nipples (hypothelia or athelia) to missing breast tissue (amastia), and names syndactyly and nail dysplasia as less common findings.  The article uses it for the row on scalp-ear-nipple syndrome.

1. 14a.

   Section Introduction:  “SEN syndrome is characterized by aplasia cutis congenita (ACC) of the scalp, breast abnormalities that range from hypothelia or athelia to amastia, and minor anomalies of the external ears ( Figure 1 ).”  Figure 1:  From the figure legend.  “Less common findings include syndactyly and nail dysplasia”. ↩ ↩

Baldelli, Ilaria et al.  “Consensus based recommendations for diagnosis and medical management of Poland syndrome (sequence).”  Orphanet Journal of Rare Diseases 15:201.  2020.  A consensus statement by Italian specialists from several fields who know Poland syndrome.  Its experts reached agreement through a slightly modified Delphi process, a series of anonymous surveys, followed by a face-to-face meeting in October 2019.  The article cites it for the statement that the cause of Poland syndrome is unknown and that most cases are sporadic, meaning they occur with no family history.

1. 15a.

   Section Etiology and pathogenesis of PS:  “To date, the etiology and pathogenesis of PS are still unknown. Most PS cases are sporadic.” ↩ ↩

2. 15b.

   Section Background:  “A subset of PS patients also have hand malformations affecting the same side and commonly including brachydactyly with or without syndactyly of the central fingers”. ↩

Levin, Roy J., and Cindy Meston.  “Nipple/breast stimulation and sexual arousal in young men and women.”  Journal of Sexual Medicine 3(3):450–454.  2006.  A questionnaire study of 301 sexually experienced undergraduates, 148 men and 153 women, aged 17 to 29, with 95% between 18 and 22.  The article uses it as evidence that male nipples have a function, since about half of the men said nipple stimulation caused or enhanced their arousal.

1. 16a.

   Section Abstract:  “A short questionnaire about nipple/breast stimulation during sexual activity was administered to 301 (148 men; 153 women) sexually experienced undergraduates (age range 17-29 years, 95% between 18 and 22).”  “In regard to the men, 51.7% reported that nipple stimulation caused or enhanced their sexual arousal, 39% agreed that when sexually aroused such manipulation increased their arousal, only 17.1% had asked to have their nipples stimulated, and only 7.5% found that such stimulation decreased their arousal.” ↩ ↩

Robinson, J. E., and R. V. Short.  “Changes in breast sensitivity at puberty, during the menstrual cycle, and at parturition.”  British Medical Journal 1(6070):1188–1191.  1977.  A study of touch and pain thresholds on the nipple, areola and skin of the breast, in 11 boys and 11 girls aged 9 to 11, six men aged 23 to 28, six women aged 20 to 22 and four pregnant women.  It found no difference between the sexes before puberty, but after puberty the women's breasts were more sensitive to touch than the men's.  The article uses it for that difference, and Jerry Bergman's 2001 article lists it as reference 13.

1. 17a.

   Page 1189, section Sex differences:  “No significant differences could be detected in either the pain or two-point discrimination thresholds between the prepubertal boys and girls (fig 1). There was also no difference between the absolute pain thresholds of the breasts of adult men and women. When the two-point discrimination data for men and women were compared, however, all areas of the women's breasts were significantly more sensitive than the men's”.  The paper gives P < 0.01 for this difference.  Methods, same page: the men were six volunteers aged 23 to 28, each tested once. ↩ ↩

Kaneda, Y. et al.  “Neither gynecomastia nor galactorrhea is a common side effect of neuroleptics in male patients.”  Neuroendocrinology Letters 21(6):447–451.  2000.  A clinical survey from the University of Tokushima that examined 100 men on regular antipsychotic treatment and a normal comparison group for breast growth and milk secretion, and measured their hormones.  It found raised prolactin in the patients but no milk in anyone, which shows how hard the male gland is to bring into function.

1. 18a.

   Section Abstract, Results:  “(1) Palpable gynecomastia was present in 2% of the patient group, but not at all in the normal group. (2) Galactorrhea was not present in either patient or normal group. (3) The mean level of the serum prolactin in the group of patients without gynecomastia (n = 53) was significantly higher than that in the normal group (n = 35)”. ↩ ↩

Kunz, Thomas H., and David J. Hosken.  “Male lactation: why, why not and is it care?”  Trends in Ecology & Evolution 24(2):80–85.  Feb 2009.  A review by a bat ecologist and an evolutionary biologist of why male mammals do not lactate, the mechanisms that can make males produce milk, and the two fruit-bat species in which wild males have been found lactating.  The article uses it for how rare male milk is.

1. 19a.

   Section Abstract:  “Mammals are characterised by their ability to provision offspring with milk, but lactation is normally restricted to females. … Until quite recently, there was no evidence for male lactation in wild mammals, but it has now been reported in two species of Old World fruit bats.” ↩ ↩

Johnson, Ruth E., and M. Hassan Murad.  “Gynecomastia: pathophysiology, evaluation, and management.”  Mayo Clinic Proceedings 84(11):1010–1015.  2009.  A clinical review by two doctors at the Mayo Clinic that describes the causes of benign growth of male breast tissue and a step-by-step diagnostic approach.  The authors rate the evidence for diagnosis and treatment as low to very low quality.  The article cites it to show that gynecomastia, a benign growth of the same retained tissue, is common.

1. 20a.

   Section Opening section:  “The prevalence of asymptomatic gynecomastia is 60% to 90% in neonates, 50% to 60% in adolescents, and up to 70% in men aged 50 to 69 years.” ↩ ↩

American Cancer Society.  Key Statistics for Breast Cancer in Men.  Jan 13, 2026.  A statistics page from the American Cancer Society, last revised 13 January 2026, that gives its estimates of breast cancer in men in the United States for 2026.  The article uses those estimates to show the cancer cost of the retained male breast tissue.

1. 21a.

   “The American Cancer Society estimates for breast cancer in men in the United States for 2026 are: About 2,670 men will be diagnosed with invasive breast cancer. About 530 men will die from breast cancer.”  “For men, the average lifetime risk of getting breast cancer is about 1 in 755.” ↩ ↩

Sarfati, Jonathan.  “Male nipples prove evolution?”  Creation Ministries International.  Feb 1, 2006.  A feedback reply, dated 1 February 2006, by Jonathan Sarfati of Creation Ministries International to readers' questions about male nipples.  The article cites it for the claim that male nipples are the result of an efficient plan of embryonic development, which is called design economy.

1. 22a.

   Section Reply to "Did Adam have nipples?":  “Quite possibly, since nipples are especially sensitive and are a source of sexual stimuli. Since they have a function, they are consistent with a design explanation.” ↩ ↩

2. 22b.

   Section Reply to "Evolution theory on the other hand easily explains male nipples":  “How so? The only explanations consistent with evolution are that humans evolved from an all-female species, or that males once helped to breast-feed their babies.” ↩

3. 22c.

   Section Closing reply:  “But even if male nipples had no known use, there is another important reason why they exist in today's males. That is, they are the result of an efficient plan of embryonic development. Human embryos are sexually dimorphic at first (i.e. contain characteristics of both sexes), because they all have basically the same genetic information, and this information is expressed as efficiently as possible as the embryo develops. This is design economy.” ↩

Mitchell, Tommy.  “Why Do Men Have Nipples?”  Answers in Genesis.  Jul 1, 2011.  A feedback reply from Answers in Genesis arguing that male nipples are a vestige of embryology, not of evolution.  The article cites it for the view that male nipples show design, and for the claim that they are a source of sexual stimulation.

1. 23a.

   “The creation model provides a much better explanation for the presence of nipples in males. Male nipples are not a vestige of evolution but are instead a vestige of embryology. They in no way diminish the abilities of the creator God, but are actually another example of His wisdom. Nipples in males are actually an evidence of "design economy."”  Later in the same reply:  “It should be noted that male nipples are not useless, as has been suggested. They are very sensitive and are a source of sexual stimulation.” ↩ ↩

2. 23b.

   “The mammary duct system and the associated nipple is likewise the same in both genders, developing during the sixth week.” ↩

3. 23c.

   “Actually, evolution posits that mammals evolved from reptiles and that the divergence of male and female took place first in reptiles. Why then would another divergence occur as humans began to evolve? In reality, if evolution were true, then it could be argued that male nipples are still developing and that men should be able to breast-feed in the future!” ↩

Bergman, Jerry.  “Is the human male nipple vestigial?”  TJ (now Journal of Creation) 15(2):38–41.  Aug 2001.  A creationist journal article arguing that the male nipple is not vestigial, because it is richly supplied with nerves and has a sexual function.  The article quotes it for the timing argument, that men keep nipples because the nipple starts forming before the male hormone signal, and for the claim that male and female nipples are equally sensitive.

1. 24a.

   Page 38, section Abstract:  “The claim that the human male nipple is vestigial, or rudimentary, is shown to be erroneous. The male nipple develops as a result of sexual differentiation, and is designed to produce sexual dimorphism.” ↩

2. 24b.

   Page 38:  “The male nipple is equally as sensitive as the female nipple.”  Bergman's footnote 15 for this sentence is M. Stoppard, The Breast Book (1996), a popular guide.  Bergman's references 9–14 on nerve supply and sensitivity include Robinson and Short 1977. ↩ ↩

3. 24c.

   Page 39:  “Men have nipples because they have already started to develop at the time when the male hormonal signal to differentiate is activated.” ↩ ↩

Javed, Asma, and Aida Lteif.  “Development of the Human Breast.”  Seminars in Plastic Surgery 27(1):5–12.  2013.  A review of how the human breast develops, written by two doctors in the pediatric endocrinology division of the Mayo Clinic.  It notes that most of what is known about the fetal breast comes from studies of rodents, and it goes through the prenatal, infant and pubertal stages.  The article uses it for the dates of the early breast stages and for the point that boys and girls do not differ at birth or in nipple size before puberty.

1. 25a.

   Section First Trimester:  “As early as 4 to 6 weeks of gestation, mammary-specific progenitor cells may be seen.”  “Around day 35 of gestation, proliferation of paired areas of epithelial cells in the epidermis of the thoracic region occurs.” ↩

2. 25b.

   Section Third Trimester:  “The surrounding areola is formed by the ectoderm during the fifth month of gestation.” ↩

3. 25c.

   Section Infant Breast:  “Soon after birth, the nipples become everted from proliferation of the underlying mesoderm”. ↩

4. 25d.

   Section Infant Breast:  “At birth, the breast is usually palpable in the newborn with varying amounts of tissue and no significant difference between the genders.”  Section Development of the Mammary Gland at Puberty:  “Sexually dimorphic development of the breast first begins at puberty”. ↩

5. 25e.

   Section Pubertal Male Breast Development:  “Until pubic hair stage 3, boys and girls do not differ in nipple diameter.” ↩

MedTerms Medical Dictionary.  Nipple absence definition.  MedicineNet.  Apr 27, 2011.  A medical dictionary entry that defines nipple absence and describes ectodermal dysplasia, a group of hereditary conditions with abnormal skin, sweat glands, eyes and teeth.  The article traces the common list of symptoms that come with missing nipples back to this entry.

1. 26a.

   “Athelia tends to occurs on one side (unilaterally) in children with the Poland sequence and on both sides (bilaterally) in certain types of ectodermal dysplasia.”  “Ectodermal dysplasia is not one but a number of hereditary conditions usually characterized by the abnormal development of skin, absence of sweat glands, dry eyes and abnormal development of teeth”.  "tends to occurs" is the page's wording. ↩

Bamshad, M. et al.  “The spectrum of mutations in TBX3: genotype/phenotype relationship in ulnar-mammary syndrome.”  American Journal of Human Genetics 64(6):1550–1562.  1999.  A genetics study that lists the TBX3 mutations found in families with ulnar-mammary syndrome and sets each family's clinical findings beside its mutation in a table.  It reports new mutations in all eight newly reported families and finds no obvious difference in symptoms between mutations that swap one building block of the protein and those that delete or shift part of the gene.  The article uses its table, which shows absent or hypoplastic (underdeveloped) areolae, the dark skin around the nipple, and underdeveloped breasts in these families.

1. 27a.

   Table 1, pages 1551–1552:  The "Breasts" column has entries including.  “Hypoplasia (B)”.  “Absent areola (B)”.  “Hypoplastic areola (B)”.  The apocrine columns include.  “Absent”.  axillary hair and perspiration.  B means both sides.  Page 1550:  Abstract, page 1550:  “Ulnar-mammary syndrome (UMS) is a pleiotropic disorder affecting limb, apocrine-gland, tooth, hair, and genital development.” ↩

Bamshad, M. et al.  “Mutations in human TBX3 alter limb, apocrine and genital development in ulnar-mammary syndrome.”  Nature Genetics 16(3):311–315.  1997.  A genetics paper that reports mutations in the human TBX3 gene causing ulnar-mammary syndrome, a rare condition that affects many parts of the body, in two families.  The article uses the abstract to describe how far the syndrome reaches across the limbs, sweat glands, teeth and genitals.

1. 28a.

   Section Abstract:  “Ulnar-mammary syndrome is a rare pleiotropic disorder affecting limb, apocrine gland, tooth and genital development. We demonstrate that mutations in human TBX3, a member of the T-box gene family, cause ulnar-mammary syndrome in two families.” ↩

van Bokhoven, Hans et al.  “p63 gene mutations in EEC syndrome, limb-mammary syndrome, and isolated split hand–split foot malformation suggest a genotype-phenotype correlation.”  American Journal of Human Genetics 69(3):481–492.  2001.  A genetics paper that looks for changes in the p63 gene in three related conditions, named in its title, and asks whether particular changes go with particular symptoms.  The article uses it for the gene behind limb-mammary syndrome, which two small families carry in a changed form.

1. 29a.

   Section Abstract:  “The original family with LMS (van Bokhoven et al. 1999 ) had no detectable p63 mutation, although it clearly localizes to the p63 locus in 3q27. In two other small kindreds affected with LMS, frameshift mutations were detected in exons 13 and 14, respectively.” ↩

Mabini, R. et al.  “Galactorrhea and gynecomastia in a hypothyroid male being treated with risperidone.”  Psychiatric Services 51(8):983–985.  Aug 2000.  A single clinical case report of milk secretion and breast growth in a man with an underactive thyroid who was taking the antipsychotic risperidone.  The article uses it as an example of the drug and disease causes of male lactation.

1. 30a.

   Section Title:  “Galactorrhea and gynecomastia in a hypothyroid male being treated with risperidone”. ↩

Franks, R. H.  “Vestigial organs: an idea destructive to medical science and our health.”  Creation 10(2):22–24.  Mar 1988.  A magazine article arguing that the idea of vestigial organs has harmed medical science and health.  Creation magazine printed it in March 1988, and creation.com has republished it online.  The article quotes it on male nipples, where the author argues that male breast tissue is an example of sexual homology, not a vestige.

1. 31a.

   Section Nipples:  “Many evolutionists reason that since male humans do not suckle the young, male breasts are vestigial. Would this mean that we are descended from some (unknown) mammal in which the male suckled the young? More informed evolutionists actually agree with the creationist that this is an example of sexual homology and has nothing to do with vestigial structures.” ↩

Menton, David N.  “Vestigial Organs: Evidence for Evolution?”  The New Answers Book 3.  Master Books.  Edited by Ken Ham.  2010.  Chapter 24 of The New Answers Book 3, edited by Ken Ham and published by Master Books in 2010.  The Answers in Genesis web version is dated 7 July 2014.  The article cites it for the claim that the male mammary gland is a vestige that can only be explained by embryology, not evolution.

1. 32a.

   Section Male Breast Tissue and Nipples:  “Vestigial mammary glands in males can only be understood in terms of embryology—not evolution. Mammary glands begin to develop in both males and females in the sixth week of gestation.”  Later in the same section:  “The male mammary gland is clearly a rudimentary or vestigial structure, but even the mammary gland of the nonlactating female might be considered vestigial.” ↩

Sanders, Lita.  “Badly designed arguments: 'vestigial organs' revisited.”  Creation Ministries International.  Nov 25, 2011.  A reply by Lita Sanders, who was born Cosner, of Creation Ministries International to a reader's list of organs said to be useless.  The article cites it for the point that male nipples are full-sized, with blood vessels and nerves, and then says that this proves less than it seems, since any patch of skin has both.

1. 33a.

   Section Male nipples:  “The existence of male nipples is attributable to design economy—both boy and girl babies develop from a common blueprint, with hormones controlling the development of sex-specific traits. It is unclear whether male nipples are useless, however. They're full-sized, equipped with blood vessels and nerves—in other words, they have everything a functioning organ has. The most commonly-cited possible purpose for them is sexual stimulation.” ↩