Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.

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 Library of Excerpts

Asian or Oriental: Heterochronic Patterns

"Mongoloid women accordingly tend to be more paedomorphic than women of other groups. Not only do women of Mongoloid origin present more prominent and rounded foreheads, but the bones of the whole skull, and, indeed, the whole skeleton, are more delicately made. Mongoloids generally tend to be shorter, and have larger heads, including larger brains --- 150 cc by volume greater, on the average, than Caucasoids. The face is flatter, the jaws and palate smaller, the nose smaller and flatter at the root (the miscalled "bridge"), and the slight fold of skin over the median part of the eye (the epicanthic fold) is preserved. The body is less hirsute, and there are fetal traits. One result of this is the high frequency of beauty among mongoloid males and females, a beauty of great delicacy (see Table I, page 21). The differential action of neoteny has produced some peculiar effects. For example, among the highly neotenized Japanese the males upper and lower jaws have been reduced in size while the teeth have not. The result has created a disharmony in many males in the form of extreme crowding and malocclusion of the teeth." (Montagu, Ashley (1989) Growing Young N.Y.: McGraw Hill pp. 40)

"The differences in dizygotic twin frequency, and presumably ovulaton rate, are in the same direction as the differences in testis size. The frequencies of dizygotic twins are even higher (up to 49 per 1,000 births) among African blacks. ... Yoruba women, with the world's highest frequency of dizygotic twins, have higher FSH and LH levels at the time of ovulation than do Japanese women, who have the lowest frequency of dizygotic twins. This variation in female hormone levels may contribute to the distribution of the incidence of breast cancer, which is known to be related to oestrogen levels. Even after all other risk factors for breast cancer have been taken into account, the incidence among Japanese women remains inexplicably low. Perhaps this puzzel, the so-called 'Japanese factor' of (breast cancer, is related to the low double-ovulation frequencies and low hormone levels." Diamond, JM (1986) Variation in human testis size. Nature (London) 320: 488-489)

“Plasma gonadotropin levels throughout the regular menstrual cycle in 10 Japanese women were measured daily using radioimmunoassay. At the peak of ovulation, mean FSH levels were 17.6 +/- 7.9 mlU/ml and mean LH levels were 75.2 +/- 26.0 mlU/ml. At midcycle, the mean gonadotropin levels were significantly lower in Japanese women than in Nigerian womenwho, as reported by Nylander (1973), had a high frequency of twinning. It is, therefore, suggested that the low frequency of dizygotic twinning in Japanese women might be related to their low output of gonadotropin. “ (Soma H, Takayama M, Kiyokawa T, Akaeda T, Tokoro K (1975) Serum gonadotropin levels in Japanese women. Obstet Gynecol 46 (3): 311)

“Salivary testosterone levels are reported for 65 Nepalese males between the ages of 15 and 48 years who were drawn from 2 different ethnic populations (Tamang [Tibetans] and Kami [Hindu Aryans]) from the central highlands of Nepal. Subjects collected morning and evening saliva samples on five consecutive days in two contrasting seasons, the winter dry season and the summer monsoon season. Anthropometric indexes of acute and chronic nutritional status were also measured. Morning and evening salivary testosterone levels in the winter averaged 233 +/- 14 (SE) pmol/L and 166 +/- 8 pmol/L, respectively, for the Tamang and 249 +/- 14 pmol/L and 163 +/- 13 pmol/L, respectively, for the Kami. In the summer the corresponding values were 219 +/- 12 pmol/L and 156 +/- 8 pmol/L for the Tamang and 249 +/- 19 pmol/L and 147 +/- 12 pmol/L for the Kami. These levels are significantly lower than those reported for Western populations and close to those reported for other non-Western populations. The magnitude of diurnal variation in salivary testosterone levels and the absence of significant age variation are also comparable with observations made on other populations. Weak relationships were observed between testosterone levels and indexes of acute and chronic nutritional status in the winter only. The absence of pronounced variation in salivary testosterone levels between populations and the absence of strong associations between salivary testosterone levels and indexes of acute and chronic nutritional status contrast with the prominent ecological and interpopulation variation reported for salivary progesterone levels in women. Male gonadal function seems less sensitive to moderate energetic stress than female gonadal function, probably reflecting the fact that energy availability is less crucial to male reproductive success than to female reproductive success. Variation in testosterone level associated with chronic energetic stress may be an adaptive somatic response to avoid the maintenance costs of a large active metabolic mass with little direct impact on male fecundity.” (Ellison PT, Panter-Brick C (1996) Salivary testosterone levels among Tamang and Kami males of central Nepal. Hum Biol 68 (6): 955)

“The Chinese Hakka, Katanganese, Temne agriculturalists and Hong Kong Chinese University students have, as expected, not only more conforming Asch scores, stricter discipline, but also the expected lower incidence of “left-handedness” (3.4%, 1.5%, 0.59% and 0.83%, respectively). In contrast, the more independent Australian Arunta hunters, Chinese Boat-People, and Alaskan Eskimo have left-hand percentages of 10.5%, 9.4%, and 11.3%, respectively, thus confirming Hy. II. The sex differences in left-handedness also supported Hy. III, with the Hakka, Temne, Katanga and Chinese agricultural males being, respectively, 3.8%, 2.5%, 0.79%, and 2.7% left-handed, while the female incidence for these societies is, 0% of a total of 330 Ss.” (Dawson, J.L.M. (1974) Ecology, cultural pressures towards conformity and left-handedness: a bio-social approach. in J.L.M. Dawson , W.J. Lonner (eds.) Readings in Cross-cultural Psychology. Hong Kong: Hong Kong U. Press. p. 136)

"Although measurements of testis size by orchidometry in living subjects are difficult to standardize, they suggest smaller testes in Japanese and Korean men than in Caucasions. Weighing at autopsy is more accurate and showed that the size was twofold lower in two Chinese samples compared with a Danish sample. Differences in body size make only a slight contribution to these values." (Diamond, JM (1986) Variation in human testis size. Nature (London) 320: 488) [note: larger African testes supports promiscous origins hypothesis, yet if African testosterone levels are higher, it refutes inverse relationship between sperm and T production]

"We do have data from Japan that are highly suggestive. Here, for many centuries, fair skins have been under parental control and, other things being equal, parents seek attractive brides for their sons. As elsewhere, members of the upper classes tend to be the luckiest. This might be expected to lead to selection as the generations have gone by. Research which I conducted a few years ago (Hulse 1967) indicated that this has taken place, for upper-class high school students have the fairest skins and those of the lower class the darkest, while middle-class students are intermdiate in pigmentation. Furthermore, data from Greece (Friedl 1962) indicate that girls who are considered good-looking marry earlier than, and need not be supplied with as large a dowry as, their less-attractive sisters. Throughout southern Europe, the upper classes contain a disproportionate number of blondes and near-blondes. Sexuall preferences, though they may be based on social snobbery rather than aesthetic interest, are capable of shifting allele frequencies in human population." (Hulse, F.S. (1978) Group selection and sexual selection in human evolution. in Evolutionary models and studies (Hague) Meier, R., Otten, C.M., Abdel-Hameed, F. (eds.), Moulton Publisher, Paris. p. 33)

"The age-standardized incidence rate [carcinoma of the prostate] varies from a low of 2.7 / 100,000 among the Japanese in Osaka to a high of 77.0 / 100,000 among Afro-Americans in the San Francisco Bay area. A study of migrant workers showed that when people moved from an area of low cancer incidence to a high-incidence area their risk for the disease increased correspondingly, suggesting that factors other than genetic makeup of the population are involved." (Ahluvalia B, Jackson MA, Jones GW, Williams AO, Mamidanna SR, Rajguru S (1981) Blood hormone profiles in prostate cancer patients in high-risk and low-risk populations. Cancer 48: 2267)

"Bolk drew attention to the findings of Muller that the Malayans of Java have much smaller thyroid glands than do Causasoids, and that the pituitary gland is heavier is Caucasoids than in Malaysians. A similar difference exists between Chinese and Causasoids. Anatomist J. Shellshear also found that the thymus gland, situated at the front of the neck and passing into the upper part of the chest, persists among the Chinese, sometimes into old age. Shellshear regarded the persistence of the thymus as an expression of retarded development, a more general evidence of which he saw in the neotenous "childlike" appearance of the Chinese---a view which both Keith and Bolk were in full agreement. In recent years investigations of the thymus gland have revealed that it secretes a number of hormones, among them a growth-promoting substance called promine. Dr. Albert Szent-Gyorgi has shown that the thymus reaches its peak when growth of the body is fastest. In his studies on bovines, Szent-Gyorgi found that the thymus is somehow connected with youth, and that extracts injected into old animals make them behave as young ones. In this respect, he stated, promine is similar in its action to the "juvenile hormone," also known as the "Peter Pan hormone," found in insects that undergo metamorphosis into butterflies. In addition to producing a large number of lymphocytes, the thymus also produces a variety of hormones and plays an important role in the development of immunologic competence in fetus and child. There is also good evidence that maturation of fetal liver and splenic cells is dependent on an intact thymus. Removal of the thymus in newborn mice stunts their growth; thymus-derived serum (gamma globulin) injected into such animals causes them to grow faster, to maintain a higher weight average, and survive almost twice as long as thymectomized controls who have been given a neutral serum." (Montagu, Ashley (1989) Growing Young N.Y.: McGraw Hill pp. 47-8)

"Thirty pairs of dichotically presented CV syllables were administered to matched samples of Native American Navajo and Anglo subjects. While sex was not a significant factor, significant differences were evidenced in the performance of the Native American Navajo and Anglo subjects. As predicted, the Navajo subjects demonstated a left ear advantage compared to the traditional right ear effect found in the Anglo subjects. These results are discussed as they relate to linguistic processing and neuropsychological theory. ... Cllinical reports of aphasic Japanese subjects have shown them to have considerable variability in their writing of Kana and Kanji characters (6-9). The Kana symbols are phonetic representations of syllables, while the Kanji characters represent the legographic properties of the characters. Recent studies have investigated the capacity of the two cerebral hemispheres in normal Japanese subjects to differentiate and process these two types of written characters {10-12}. The results of these studies have indicated that the two cerebral hemispheres do differentially process Kana and Kanji characters. The Kana (phonetic) symbols seem to be processed in the left cerebral cortex while the Kanji (logograhic) characters are more reliably reported when projected to the right cerebral hemisphere. These results seem to be consistent whth the clinical observations noted in aphasic Japanese patients {6-9} and are intriquing for several reasons. First, reading these symbols in Japanese appears to require a more neurologically integrated effort than reading English, as it seems to involve the processing of symbols in both cerebral hemispheres rather than in the left cerebral cortex, which seems to be the case with English. Second, one could speculate that some mechanism must scan the characters and, based on their stimulus properties, shift attention transcallosally to the appropriate hemisphere. Finally, these studies suggest that cerebral function for written Japanese may be less fully lateralized in Japanese subjects as is traditionally reported in the contempory literature for English-speaking subjects. If this is indeed the case, there may be other populations in which language lateralization differs relative to our current understanding of neuropsychological asymmetries. There is some very limited evidence that lateralization for language in the Native American Hopi differs more dramatically than would be expected {13}. Using an analysis of EEG ratios, these investigators found a significant right cerebral hemisphere specialization for language processing in Hopi Indian children." (Scott, S., Hynd, G.W., Hunt, L. & Weed, W. (1979) Cerebral speech lateralization in the American Navajo. Neuropsychologia 17: 89)

The ethnographic record {e.g., A French Army Surgeon (1898/1972), a 30-year specialist in genitourinary diseases} makes reference to numerous anatomical distinctions which show a similar pattern of whites being between blacks and Orientals. These include the placement of female genitals (Orientals front and high; blacks back and low); angle and texture of erection (Orientals parallel to body and stiff, blacks at right angles to body and flexible); salient buttocks, breasts, and muscularity (Orientals least, blacks most); and size of genitalia (Orientals smallest, blacks largest). We averaged the ethnographic data on erect penis and found the means to approximate: Orientals, 4 to 5.5 in. in length and 1.25 in. in diameter; Caucasions, 5.5 to 6 in. in length and 1.5 in. in diameter; blacks, 6.25 to 8 in. in length and 2 in. in diameter. Women were proportionate to men, with Orientals having smaller vaginas and blacks larger ones, relative to Caucasians. Clitoral size differed in length: in European women, 1.2 in.; in African women, 2 in. variations were noted; in French West Indies, the size of the penis and vagina covaried with amount of black admixture; Arab men, who were often mixed with black, had larger penises than Europeans. Recent data show similar patterns. Measurements taken from living subjects as well as those at autopsy, show the size of testes is twofold lower in Asian men than Europeans (9 g vs 21 g), a difference too large to be accounted for entirely in terms of body size (Diamond, 1986; Short, 1984). Concomitantly, as mentioned, Asian women have lower ovulation rates than Caucasian women, as indexed by dizotic twin frequency, with the frequency per 1000 across several Asian populations being < 4, while for Caucasians it is 8, and for blacks 16 per 1000 (Bulmer, 1970; Diamond, 1986). Contrary to the general trend, Freeman (1934) observed that, at autopsy, American blacks had less heavy testes than American whites (13g vs 15g). Freeman (1934), however, did find that black women had heavier ovaries than white women. Subsequently Daniel, Fienstein, Howard-Peebles, and Baxley (1982) found no black-white difference in testicular volume among American adolescents, while Ajmani, Jain, and Saxena (1985) found larger scrotal circumference in Nigerians than Europeans (212.6 mm vs 195.1 mm or 8.37 in. vs 7.68 in.). A French Army Surgeon (1988/1972) also provided early observations that, in speed of sexual maturation, Orientals < whites< blacks. Several subsequent studies are confirmatory. In the United States, blacks are more precoscious than whites as indexed by age at menarche, first sexual experience, and first pregnancy (Malina, 1979). A national probability sample of American youth found that by age 12, 19% of black girls had reached the highest stages of breast and pubic hair development, compared to 5% of white girls (Harlan, Harlan, & Grillo, 1980), although the same survey found white and black boys to be similar (Harlan, Grillo, Coroni-Huntley, & Leaverton, 1979). Subsequently, Westney, Jenkins, Butts, and Williams (1984) found that 60% of 11-year-old black boys had reached the stage of acelerated penis growth in contrast to the white norm of 50% of 12 1/2-year-olds. This genital stage significantly predicted onset of sexual interest, with 2.2% of the black boys experiencing intercourse by age 11. While some surveys found that Oriental girls enter puberty as early as whites (Eveleth & Tanner, 1976), others suggest that in both physical development and onset of interest in sex, the Japanese, on the average, lag 1.5 to 2 years behind white Americans (Asayama, 1975). (Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal Research in Personality 21(4): pp. 536-7)"As can be seen in Table 2, the results showed that African adolescents are more sexually active than Europeans, who are more sexually active than Asians." (Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal Research in Personality 21(4): pp. 535)

"The rate of premarital intercourse is matched by that following marriage. We inspected a section on cross-cultural intercourse frequency in a review by Ford and Beach (1951) and categorized the tribal peoples listed into three main groups. The Oceanic and Amerindian peoples tended to a lower per week average (1-4), than U.S. whites (2-4), than Africans (3-10). Recent surveys support the same conclusion. For married couples in their 20's, the average frequency per week of intercourse for the Japanese approximates 2 (Asayama, 1975), for American whites 4, and for American blacks, 5 (Fisher, 1980)." (Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal Research in Personality 21(4): pp. 535)

"Conjecturing as to physiological mechanisms, one hypothesis implicates testosterone and other sex hormones. Freeman (1934) found differences in the weight of the hypophysis (pituitary) with blacks having the heaviest (800 mg), whites being intermdiate (700 mg), and Orientals the lightest (600 mg). The pituitary is directly involved with the release of gonadotropins which stimulate the testicles and ovaries in their functions (the release of testosterone, estradiol, and progesterone on the one hand, and sperm and eggs on the other)." (Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal Research in Personality 21(4): pp. 546)

"The issue of whether populations differ in brain size remains controversial. Cranial capacities were calculated from external head measurements reported for a stratified random sample of 6,325 U.S. Army personnel measured in 1988. After adjusting for the effects of stature and weight, and then, sex, rank, or race, the cranial capacity of men averged 1,442 and women 1,332 cm3; that of officers averaged 1,393 and enlisted personnel 1375 cm3; and that of Mongoloids averaed 1,416. Caucasoids 1.380, and Negroids 1,359 cm3. (Rushton, J.P. (1992) Cranial capacity related to sex, rank, and race in a stratified random sample of 6325 US military personnel. Intelligence 16 (3-4): pp. 401)

"Caucasian men have, on average, a larger cranial capacity than do their Mongoloid counterparts, whereas Mongoloid women have a larger cranial capacity than do Caucasian women. Negroid men and women have smaller cranial capacities than do Mongoloid and Caucasoid men and women." (Rushton, J.P. (1992) Cranial capacity related to sex, rank, and race in a stratified random sample of 6325 US military personnel. Intelligence 16 (3-4): pp. 405)

"The groups with the earliest median age for menarche (first mentrual period) are the well-off in Istanbul (age 12.3), Singapore (12.4) and Hong Kong (12.5), and Afro-Americans (12.5). Those with the latest menarche are in New Guinea and East Africa (15.5 to 18.0)." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 275)

"Asiatics, even those who are growing up under the best circumstances, are less tall at all ages than well-off Europeans and Africans. Chinese and Japanese mature as early or earlier than well-off Africans and considerably earlier than populations in Northwest Europe.....At puberty Asiatics have a different pattern of skeletal maturation from Europeans and Africans, increasing their rate of maturing more swiftly and reaching full skeletal maturity earlier." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 274)

"Chinese in Hong Kong have one of the earliest recorded medians (12.5 for well-off, 12.8 for middle class and 13.3 for poor) and Japanese are relatively early (12.9). New Zealand Maori are earlier (12.7) than New Zealand Europeans (13.0), both figures being derived from a full national survey (Fig. 167). Though Africans in Africa, even those apparently well-off, are relatively late (13.4, Uganda; 14.1, Nigeria), Afro-Americans are early, averaging 12.5 (Fig.167). People largely of European-African mixture in Cuba average 13.0 over the whole island, but about 12.6 in Havana. It seems likely, therefore, that in good environmental conditions Africans may be as early-maturing in this parameter as Asiatics and southern Europeans, and earlier than the peoples of Northern and Central Europe. Girls in the Near East have a relatively late menarche, with the exception of well-off girls in Istambul who at 12.3 have the earliest median of any population studied. Even the poor in Estanbul average 13.2 years. In India the well-off average about 12.8, and the poor up to 14.5. The people with the latest menarche are the Melanesians of New Guinea, having medians ranging from 15.5 to 18.4 years (Fig. 167). Menarche is delayed by chronic undernutrition. In the poor rural area of 'Appalachia' in the southern United Stated thirty undernourished Euro-American girls followed longitudinally had a mean menarcheal age of 14.4 years against 12.4 in the well-nourished controls (Dreizen, Spirakis & Stone, 1967). They were likewise delayed in skeletal maturation and shorter in height during childhood, though they reached the height of the controls at maturity. ... In the nineteenth century menarche occured on average around 15 years in England and in Norway and Finland at nearly 17 years (Tanner, 1966c). The trend shown in Fig. 168 (a) represents about 0.3 years per decade. There is some evidence that this trend is now stopping...." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 213-217)

"Afro-American girls have menarche some 0.3 years earlier than European-descended girls (12.5 compared to 12.8 years) and in both sexes dental and skeletal development is advanced in Afro-Americans (Garn et al., 1972a,b). Thus, part of their greater height is due to earlier maturation. Figs. 173 and 174 show the weight curves. Whereas Washington and London children are quite similar from 1 year until puberty, birth weights appear to be lower in African descendants when US samples adjusted for income, maternal age, parity and smoking and compared (Penchaszadeh et al., 1972). Hong Kong Chinese are lighter at every age. Thus they are lower in weight-for-height than London and Washington children, who are similar. In summary then, Afro-American children growing up under favorable conditions are a little taller and heavier than Europeans and Euro-Americans living in the same cities. This is partly or wholly because they are a little more advanced in maturity. Asiatics, on the other hand, under equally favourable circumstances are smaller despite being still further advanced in maturity." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 229)

"Skeletal maturation is slower in lower socio-economic groups compared with upper and middle groups. An example from Hong Kong is shown in Fig. 161; the middle groups were intermediate (Low et al., 1964). The characteristic Asiatic increase in rate at adolescence began a year earlier in the better-off boys and earlier still in the better-off girls (not shown in Fig. 161)." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 203)

"The greatest retardation in the populations considered here is found among the highland Quechua Amerindians. Delays of 14% to 58% (according to centre) in boys, and 11% to 91% in girls have been reported for the early childhood ossification centres. ... The comparisons discussed above, together with the older results (summarised in Tanner, 1962, p. 62), show that African children under good nutritional and environental circumstances are more advanced than Europeans in skeletal development from birth to adolescence. There are no data showing whether the advancement continues into adolescence, though it seems probable. Quite a different picture emerges for Asiatics, represented by Chinese and Japanese. Although similar during childhood to Europeans they become advanced at adolescence." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 206)

"The most interesting observation to be drawn from Figs. 101 and 102, however, is that while California Japanese boys are still slightly taller than the 1970 Japanese sedente boys, those measured in 1971 in California, who are mostly second and third generation (sansei), are not sensibly taller than those measured in 1956-7, who were first generation (nissei; that it, their parents were immigants). Thus there seems to be little recent further increase in height amongst the Japanese boys living in California. Perhaps the 1970 population is approaching its genetic size limits (see Chapter 9). There might, however, be some differences in social selection between the two California samples of which we are not aware. Greulich's study was done in the San Francisco Bay area and according to the author no special selection of subjects was made. Kondo & Eto's study was in the greater Los Angeles area, but their method of chooding children is not stated. As regards girls, all three Japanese populations are very similar until after puberty. Then California sansei (1971) girls continue to gain, ending up taller at 15, 16, and 17 years. The California Japanese studied in 1956-7 were considerably taller than the Japanese in Japan at that time (1953), even though they are not taller than the Japanese today." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 136)

"The populations themselves show no striking departures from the overall regression, however. By 16 years (Fig.131) boys' and girls' plots are clearly separated. This occured also in European populations, but not in African or Asiatic ones." [less dimorphic?] (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 169)

"However, there is a high population-specificity with respect to these glands: about half of Koreans and Japanese lack any apocrine glands at all in their armpits (Morris, 1985, p. 141). (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 169)

"Thus, the human penis shows high species-specificity as an elaborated genital structure. Penis size also varies moderately across populations, being largest among African populations, smaller among European populations, and smallest among East Asian populations, but with substantial overlap (Rushton, 1987, 1988b, 1989b). Penises are highly age-specific, attaining their full resting size only after puberty, and are highly courtship-specific, attaining their full erect size only under sexually arousing conditions. Thus, penises show all the hallmarks of a morphological trait elaborated somehow through sexual selection." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 185)

"The rate of monozygotic twinning is very much the same throughout the world: about 3 twin births per 1000. The dizygotic twinning rate, however, varies considerably. Thus, some older data showed that in Japan there was approximately 1 dizygotic twin birth out of 165, whereas in the northern countries of Ireland and Scotland the rate was about three times as high. The rates in northern Europe are generally of this order, and those in southern Europe are lower (Bulmer 1970). The highest twinning rates so far observed occur in West Africa, particularly among the Yoruba, especially in the vicinity of Ibaden, where the rate is about 1 in 18 births. In young Yoruba women of high parity the rate of twinning may be nearly 1 in 10 births. It is no surprise that twin dolls are a characteristic feature of Yoruba art. In the United States, Blacks (most of West African descent) have higher twinning rates, and Orientals have lower twinning rates than Caucasians (Bulmer 1970).

"Teng et al. (1976) pointed out that cases of pathological left-handedness will constitute a higher proportion of the population of all left-handers in countries such as China where there is strong social pressure to be right-handed. They found that twinning was associated with both decreased right-handedness and reduced college entrance is a large Taiwanese population, which is consistent withthe view that there is an excess of left-handedness among twins due to the influence of pathological factors. This suggests that if we could find some independent way of discriminating between pathological and natural left-handers in Wesern cultures (see p.95), we might be able to obtain clearer evidence for different distributions of handedness in twins and singletons. However, against this view is Annett's (1985) finding of a significant excess of left-handers among twins as compared to singletons even when probable pathological left-handers (those scoring more than two standard deviations below the mean on a test of manual dexterity) were excluded from consideration." (Bishop, D.V.M. (1990) Handedness and Developmental Disorder. MacKeith, Manchester pp. 36)

"There is also a high rate of neural tube defects in many populations in which dizygotic twinning is common, as it is in Ireland and Scotland. In China, where the rate of dizygotic twinning is very low, neural tube defects occur about one-tenth as frequently as in Ireland (Ghosh et al. 1981). It is very possible that the rate of twin conceptions is higher than is generally appreciated, since in some cases one fetus may die and be reaborbed. The rate of twinning has been falling in recent years in Europe, as has the rate of neural tube defects, data for which no satisfactory explanation has yet been found." (Geschwind & Galaburda 1987: 140-41, Cerebral Lateralization)

"Buttock size also shows moderate population-specificity, being fairly small among East Asian populations and larger among European and African populations. Among the Kalahari bushwomen and the Hottentots, female buttock size is particularly exaggerated into a condition known as "steatopygia"; this condition bears no clear relation to any ecological requirement for fat storage." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 203)

"After adjustment for age, Quetelet's index, and physical activity, levels of testosterone (total, free, and bioavailable) were higher for Asians born in Asia versus for those Asians born in North America, whereas levels of SHBG and DHT were similar in both groups (Table 4). On the other hand, the DHT: testosterone ratio was lower in Asians born in Asia compared to those born in North America. However, none of the differences between Asians born in North America and those born in Asia were statistically significant." (Wu, A.H., Whittemore, A.S., Kolonel, L.N., John, E.M., Gallagher, R.P., West, D.W., Hankin, J., Teh, C.Z., Dreon, D.M., & Paffenbarger, R.S.Jr. (1995) Serem androgens and sex hormone-binding globulins in relation to lifestyle factors in older African-American, white, and Asian men in the United States and Canada. Cancer Epidemiology, Biomarkers & Prevention 4(7): pp. 739)

"Less than 1% of Japanese school-children were reported by Komai and Fukuoka (1934) to use the left and for writing, but incidences of left-handed throwing, cutting with scissors, striking a match, and kicking a football (5-8.5%) were comparable to those found for English children today (Chapter 10). Chinese children were found to use the left hand rarely for eating (1.5% or writing (.7%) in Taiwan but more often (6.5%) in the United States (Teng, Lee, Yang, & Chang, 1976). A population sample of parents and children in Hawaii is especially interesting because differences in incidences of left-handed writing were found between parents of different ethnic origin (Japanese versus European) but not between their children, presumably because of an easing of social sanctions against left-handedness in Japanese families living in Hawaii (Ashton, 1982). A difference between generations, with more left-handers among children than parents, has been found in all studies of the families of university students (Tables 3.6 and 16.7). It was also found for both ethnic groups in Ashton's (1982) sample, which was not university-based. A questionnaire given to Londoners attending a dental hospital for treatment found about 10% left-handed writers in younger respondents (15-44 years) but only about 3% in older respondents (55-64 years) (Fleminger, Dalton, & Standage, 1977). Burt (1937) reported incidences of 3-4% in his studies in his schools of 1913 and 1923, at about the time the older Londoners were at school. Studies of trends in adult populations in the United States (Porac, Coren & Duncan, 1980) and in Australia (Brackenbridge, 1981) have documented falling incidences of left-handedness with increasing age." (Annett, Marian (1985) Left, Right, Hand and Brain: The Right Shift Theory London: Lawrence Erlbaum pp. 68-9)

"There is no reason to believe, on present evidence, that the distribution of L-R skill differs between Oriental and Western samples (Ashton, 1982), or that there are differences in extent of right shift." (Annett, Marian (1985) Left, Right, Hand and Brain: The Right Shift Theory London: Lawrence Erlbaum pp. 258)

[from abstract] "Clinically apparent prostate cancer occurs more commonly among Caucasians living in Western countries than in Chinese in the Far East. Prior studies demonstrated diminished facial and body hair and lower levels of plasma 3 alpha-androstanediol glucuronide and androsterone glucuronide in Chinese than in Caucasian men. Based upon these findings, investigators postulated that Chinese men could have diminished 5 alpha-reductase activity with a resultant decrease in prostate tissue dihydrotestosterone levels and clinically apparent prostate cancer. An alternative hypothesis suggests that decreased 3 alpha-androstanediol glucuronide and androsterone glucuronide levels might reflect reduced production of androgenic ketosteroid precursors as a result of genetic or environmental factors. The present study examined 5 alpha-reductase activity, androgenic ketosteroid precursors, and the influence of genetic and environmental/dietary factors in groups of Chinese and Caucasian men. We found no significant differences in the ratios of 5 beta-:5 alpha-reduced urinary steroids (a marker of 5 alpha-reductase activity) between Chinese subjects living in Beijing, China, and Caucasians living in Pennsylvania. To enhance the sensitivity of detection, we used an isotopic kinetic method to directly measure 5 alpha-reductase activity and found no difference in testosterone to dihydrotestosterone conversion ratios between groups. Then, addressing the alternative hypothesis, we found that the Caucasian subjects excreted significantly higher levels of individual and total androgenic ketosteroids than did their Chinese counterparts. To distinguish genetic from environmental/dietary factors as a cause of these differences, we compared Chinese men living in Pennsylvania and a similar group living in Beijing, China. We detected a reduction in testosterone production rates and total plasma testosterone and sex hormone-binding levels, but not in testosterone MCRs in Beijing Chinese as a opposed to those living in Pennsylvania. Comparing Pennsylvania Chinese with their Caucasian counterparts, we detected no significant differences in total testosterone, free and weakly bound testosterone, sex hormone-binding globulin levels, and testosterone production rates. Taken together, these studies suggest that environmental/dietary, but not genetic, factors influence androgen production and explain the differences between Caucasian and Chinese men." (Santner SJ, Albertson B, Zhang GY, Zhang GH, Santulli M, Wang C, Demers LM, Shackleton C, Santen RJ (1998) Comparative rates of androgen production and metabolism in Caucasian and Chinese subjects. J Clin Endocrinol Metab 83(6):2104-2109)

"A number of investigators have studied the effects of malnutrition on tooth eruption (Graham & Morales, 1963; Cifuentes & Alvarado, 1973; Neill et al., 1973; Truswell & Hansen, 1973). Infants who are small-for-dates have a delayed eruption. Eruption is delayed also in triplets and higher order multiple births. Possibly infants with severe protein-calorie malnutrition are delayed, but if so, the effect is considerably less on dentition than it is on weight, height or skeletal development (Meredith, 1973; Robinow, 1973). Hong Kong Chinese infants (Billewicz, Thomson, Baber & Field, 1973) do not differ significantly in deciduous eruption times from Newcastle British (Billewicz et al., 1973) or New Guineans (Bailey, 1964b)(Fig. 163; Appendix Table 107). Generally, Australian Aborigines, Bengalis, Hindus, Nigerian villagers and Gambians (not shown in Fig. 163) have slightly delayed eruption. The two Nigerian samples are interesting in showing environmental contrasts (Enwonwu, 1973). Both groups are Yoruba, but one comes from the group of Ibadan privileged that we have examined before in other parameters of growth, and the second in derived from the rural villages of Osgere and classed as underprivileged. The well-off group has by far the most advanced eruption, not only compared with the villagers, but with all the groups shown in Fig. 164. These Nigerian data throw some doubt on the wisdom of using number of erupted primary teeth as a guide to chronological age in tribal groups where age is not known. This has been advocated by various authors (Bailey, 1964b, Brook & Barker, 1973; Malcolmm 1973; Billewicz, 1973) on the grounds that it is less affected by sex, race and poor nutrition than any other indicator." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 207-8)

"Whereas there are no clear differences between ethnic groups in the age of eruption of deciduous teeth, there are marked ones in the permanent dentition (Figs. 165 and 166; Appendix Table 109). Most investigators agree that the peoples of New Guinea, together with Africans in Africa and the United States, are the most advanced." (Eveleth, P.B. & Tanner, J.M. (1976) Worldwide Variation in Human Growth: Cambridge Univ. Press, London p. 210)



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