FOUNDATIONS FOR SEX 



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the normal diploid would be expected to 

 lead to the complex changes. Mongolism is 

 influenced by age of the mother and prob- 

 ably to some extent by her inheritance. It 

 is to be expected that the other trisomies 

 may show parallel relations. Other trisomies 

 may be expected although, as the chromo- 

 somes increase in size, a group of them will 

 have less opportunity to survive because of 

 loss of balance with the rest of the diploid 

 set. Thus far most of these conditions af- 

 fect the sex phenotypes. This is in accord 

 with the results in Drosophila. Changes in 

 the balance of the X chromosomes are less 

 often lethal than the gain or loss of an auto- 

 some. Other animals show like effects. In 

 plants, loss or gain of a chromosome, al- 

 though generally detrimental, often causes 

 less severe restrictions on life. Harmful ef- 

 fects are observed but do not cause early 

 deaths. This may be because many aneu- 

 ploids are within what are presumably 

 polyploid plant species. 



Ford (1960) has collected the data on 13 

 different phenotypes that could come under 

 suspicion of chromosomal etiology as ex- 

 amined by a number of workers. Careful 

 cytologic examination of patients suffering 

 from one or another of these diseases has 

 shown that the idiograms were normal in 

 both number and structure of the chromo- 

 somes. The disease conditions were: 

 acrocephalosyndactyly, arachnodactyly 



(Marfan's syndrome), chondrodystrophy, 

 Crouzon's disease, epiloia, gargoylism, Gau- 

 cher's disease, hypopituitary dwarfism, 

 juvenile amaurotic idiocy, Laurence-Moon- 

 Biedl syndrome. Little's disease, osteogene- 

 sis imperfecta, phenylketonuria, and anen- 

 cephalic types. To this list Sandberg, Koepf , 

 Crosswhite and Hauschka (1960) have now 

 been added neurofibromatosis, Lowe's syn- 

 drome, and pseudohypoparathyroidism. 



F. SEX RATIO IN MAN 



Sex ratio studies on human and other ani- 

 mal populations have always been large in 

 volume. The period since 1938 is no excep- 

 tion. Geissler's (1889) data on family sex 

 ratios, containing more than four million 

 births, have been reviewed and questions 

 raised by several later analysts. Edwards 

 (1958) has reanalyzed the clata from this 

 population and considered these points and 



reviewed the problems in the light of the 

 following questions: (1) Does the sex ratio 

 vary between families of the same size? (2) 

 Do parents capable of producing only uni- 

 sexual families exist? (3) Can the residual 

 deviations in tlie data be satisfactorily ex- 

 plained? Probability analyses were based 

 on Skellam's modified binomial distribution, 

 a special case of the hypergeometrical. The 

 following conclusions were drawn. The 

 probability of a birth being male varies 

 between families of the same size among 

 a complete cross-section of this 19th century 

 German population. There is no evidence 

 for the existence of parents capable of pro- 

 ducing only unisexual families. With the 

 assumption that proportions of males vary 

 within families, the apparent anomalies in 

 the data appear to be explicable. These 

 studies have a bearing on the variances ob- 

 served in further work dealing with family 

 differences such as that of Cohen and Glass 

 ( 1959) on the relation of ABO blood groups 

 to the sex ratio and that of Novitski and 

 Kimball (1958) on birth order, parental age, 

 and sex of offspring. Novitski and Kim- 

 ball's data are of basic significance, for the 

 interpretations are based on a large volume 

 of material covering a one-year period in 

 which improved statistical techniques were 

 utilized in the data collection, in showing 

 that within these data sex ratio variation 

 showed relatively little dependence on age 

 of mother, whereas it did show dependence 

 on age of father, birth order, and inter- 

 actions between them. These observations 

 have direct bearing on the larger geographic 

 differences observed in sex ratios as dis- 

 cussed by Russell (1936) and have recently 

 been brought to the fore through the studies 

 of Kang and Cho (1959a, b). If these data 

 stand the tests for biases, they are of signifi- 

 cance in showing Korea to have one of the 

 highest secondary sex ratios of any region, 

 113.5 males to 100 females, as contrasted 

 with the American ratio of about 106 males 

 to 100 females. Of similar interest is the 

 lower rate of twin births, 0.7 per cent in 

 Korea vs. about 1 per cent in Caucasian 

 populations and the fact that nearly two- 

 thirds of these tW'in births in Korean peoples 

 are identical, whereas those in the Cauca- 

 sian groups are only about half that num- 

 ber. The reasons for these differences must 



