234 Or at least it needs its Leydig cells. The testosterone synthesis pathway can be upset at many points. Luteinising hormone is needed for proper Leydig cell growth. Mutations in the luteinising hormone receptor gene (152790) cause Leydig cell hypoplasia and so pseudohermaphroditism (Kremer 1995 and Laue et al. 1996). Then various mutations can disrupt the testosterone biosynthetic pathway (Besser and Thorner, 1994). Some of these cause a group of syndromes known as the congenital adrenal hyperplasias (CAH) (e.g. 201910) since they affect not only testosterone synthesis but the synthesis of other steroids by the adrenal gland as well and have, accordingly, widespread physiological effects. Good examples of testoterone synthesis mutations are those in the 17-? hydroxysteroid dehydrogenase gene (605573) (Russell et al. 1994; Geissler et al. 1994).
235 Such girls are, it is often said, exceptionally feminine. Androgen insensitivity syndrome (300068) caused by mutations in the testosterone receptor gene (313700). For the height of testosterone receptor-null people see Quigley et al. (1992). For the identical twin flight attendants see Marshall and Harder (1958); for the French model see Netter et al. (1958).
236 Alexina/Abel and Marie/Germain were both isolated cases. Montaigne, the humanist, attributed Marie/Germain’s sex change to sublimated sexual desire; Pare, the (evidently Vesalian) surgeon, thought that the exertion of the chase had caused Marie’s genitals to fall out. Montaigne (1580; 1958) p.38; Paré (1573; 1982) p.31. For the Dominican Republic guevedoche see Imperato-McGinley et al. (1974); for the Papua New Guinea kwolu-aatmwol see Imperato-McGinley et al. (1991). The mutated gene in all these cases has either been shown, or else is presumed to be, 5-?-reductase (264600; 607306).
238 When I said that the route to femininity. For infant female pseudohermaphroditism caused by deficiency in aromatase (107910) see Shozu et al. (1991); for the adult aromatase deficiency see Conte et al. (1994) and Morishima et al.(1995). For aromatase excess (shortness, gynecomastia in boys, large breasts in girls) due to dominant gain-of-function mutations, see Stratakis et al. (1998).
240 Spotted hyenas are unsympathetic creatures. See Neaves et al. (1980); Glickman et al. (1992); Licht et al. (1992); Holekamp et al. (1996) and Frank (1997) for spotted hyena endocrinology, genitalia and social structure. Moles (Talpa) also have a kind of female pseudohermaphroditism – although they actually have ovotestes, so could be said to be true hermaphrodites.
242 In The symposium. Plato, The symposium pp.59–65 (trans. W. Hamilton. 1951. Penguin Books, Harmondsworth, UK). For sexual relations of the guevedoche and kwolu-aatmwol see Imperato-McGinley et al. (1991) and Herdt (1994).
CHAPTER VIII: A FRAGILE BUBBLE
247 Our species has, since 1758. Bendyshe (1865) gives a summary and English translation of Linnaeus’ anthropological works; Pearson et al. (1913) and Broberg (1983) discuss Homo troglodytes. Lindroth (1983) discusses Linnaeus’ intellectual roots in medieval thought.
251 His French rival Buffon. For an account of Geneviève see Buffon (1777)Addition à Particle qui a pour titre, Variétés dans l’espèce humaine, Supplement à l’histoire naturelle volume 4 pp.371–454.
253 We are a polychrome species. For a general review of pigmentation genetics see Sturm et al. (1998). The most common form of albinism is oculocutaneous albinism type 1 or OCA1 (203100), which is due to recessive mutations in the tyrosinase gene (606933). Albinism with grey eyes is oculocutaneous albinism type 2 or OCA2 (203200), due to recessive mutations in the P gene (Durham-Pierre et al. 1994; Stevens et al. 1997).
254 In 1871, en route to his encounter with the Aka. See Schweinfurth (1878) volume 2 pp.100–1 for his account of albinos in Africa, and Woolf and Dukepoo (1969) for albinos among the Hopi.
255 Those children would have fascinated Buffon. For the history of Marie Sabina see Buffon (1777) p.557. Pearson et al. (1913) and Dobson (1958). For some of the other eighteenth-century piebalds see Blanchard (1907). For Lisbey’s history see Pearson (1913). Pearson’s insistence on this rather forced account of the inheritance of piebaldism stems, again, from his opposition to the Mendelian theory of inheritance.
261 Molecular devices are required. Piebald trait, white forelock and bilateral hypopigmentation of the limbs and trunk (172800) is caused by dominant mutations in c-Kit (164920) which encodes a receptor tyrosine kinase. c-Kit’s ligand is steel (Sl) in mouse, but no human disorder has been identified with mutations in this gene. c-Kit and its ligand are thought to help in guiding the migration of the presumptive melanocytes. The other piebald syndromes often only cause white forelock but are associated with deafness or megacolon. These are Waardenburg’s syndromes types I through IV (193500, 193510, 602229), caused by dominant mutations in Pax3, Sox10 and MITF (Tassabehji et al. 1992; Watanabe et al. 1998). These genes are transcription factors needed for specification of melanocyte lineages (Goding 2000). All these syndromes manifest variably, all are caused by dominant mutations; homozygotes are probably lethal.
261 What gives us our skin colours? Africans differ from Europeans, and East Asians are known to differ in the structure and density of their melanosomes (Szabó et al. 1969; Toda et al. 1972), but very little is known about the genetics – except for a hint it might have something to do with the P gene (Sturm et al. 1998). See Linnaeus (1758) pp.20–1 for his diagnosis of the human species; a translation is given by Robins (1991) p.171.
262 For nearly half a century. The history of race-classification in South Africa is discussed by Posel (2001). Rita Hoefling’s story is told by Joseph and Godson (1988).
265 Life growth hormone, melanotropins. Red hair and obesity are caused by mutations in POMC (176830), a gene that encodes the ?-MSH and ACTH precusor (Krude et al. 1998).
266 Yet not all redheads are fat. Red hair (266300) caused by recessive mutations in the MC1R gene (155555) (Robbins et al. 1993; Valverde et al. 1995; Smith et al. 1998; Flanagan et al. 2000; Healy et al. 2001). Besides the general plausibility arguments that I have given as to whether red hair has been selected or not (Darwin 1871, 1981 volume 2 pp.316–405; Robins 1991 pp.59–72) and is therefore properly thought of as a mutation or polymorphism, there are also elaborate statistical tests which can sometimes detect historical patterns of selection. Such tests have been applied to MC1R, but they are inconclusive (Rana et al. 1999; Harding et al. 2000).
268 Pale, and proud of it. For a detailed discussion of the pre-PRC history of Chinese anthropology and eugenic thought see Dikötter (1992, 1997, 1998). For a study of Ainu hairiness see Harvey and Broth well (1969).