Timing of Fertilization and the Sex Ratio of Offspring

James, William H.

doi:10.1016/b978-0-12-088860-3.50009-x

Cited by 18 publications

(12 citation statements)

References 68 publications

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“…Unlike the results of many previous studies, mainly among European, American, and some Asian populations (James 1983, the SSR of the higher birth order category was essentially as high as that of the group of lower birth order (Table 2). This pattern is even accentuated and is statistically highly significant for offspring of parents born before 1895, many of whom would have completed reproductive histories by 1941 (Table 3).…”

contrasting

confidence: 83%

Sex ratio of livebirths in Micronesia

Underwood

1995

American J Hum Biol

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A growing body of data extends Hunt's earlier findings from Yap to suggest a characteristic Micronesian pattern of highly masculinized secondary sex ratios. Using materials from an extensive family record register for pre-World War II Guam, it is now possible to examine parental age and birth order effects in a Micronesian population in which the overall sex ratio of livebirths to 3,406 formally wed and fertile couples was 109.6. In contrast to the results of most studies among Euroamerican groups, secondary sex ratios on Guam were significantly higher for higher order births and for paternal age at last recorded birth to older couples. This apparent anomaly is resolved, however, and James' hypothesis of human sex ratio determination is supported when universalistic assumptions of declinin coital frequencies with spousal age and marital duration are replaced by more appropriate and population-specific ethnodemographic information. © 1995 Wiley-Liss, Inc.

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contrasting

confidence: 83%

Sex ratio of livebirths in Micronesia

Underwood

1995

American J Hum Biol

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“…The mechanism of this effect on sex ratio is uncertain. Although the effect could possibly be operating through a third variable such as parental age, parity, or race (James, 1984a;1985), the evidence that changes in caloric supply are related to changes in the sex ratio within the same country argues against a mediating variable. By the same token, it is possible that caloric availability may be mediating the relationships that exist between sex ratio and parental age, parity, and race.…”

Section: Discussionmentioning

confidence: 99%

“…Fewer males are born to fathers with high levels of stress (Little, Rigsby, and Little, 1987;Schuster and Schuster, 1972). Couples with low coital rates are less likely to produce males (James, 1983;19876) (less fit males, either because of age or dominance status, are likely to have lower coital rates).…”

mentioning

confidence: 99%

“…Nevertheless, many factors known to be associated with variations in the sex ratio at birth appear to have adaptive value. Fewer males are born with increasing birth order (James, 1987a;James and Rostron, 1985;Ruder, 1985) or multiple births (Bulmer, 1970;James, 1975), perhaps because of greater sibling competition for resources. Fewer males are born with increased paternal age, and, to a lesser extent, with increased maternal age (James, 1987a;James and Rostron, 1985;Ruder, 1985).…”

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confidence: 99%

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Human sex ratio as it relates to caloric availability

Williams

Gloster

1992

Biodemography and Social Biology

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ABSTRACT:The relationship between human sex ratios at birth and caloric availability per capita was examined across different countries. Significant positive correlations were obtained between the amount of food a country had available and the percentage of male births. Furthermore, increases or decreases in a country's caloric availability were related to corresponding changes in that country's sex ratio. These results provide evidence of adaptive sex ratio biasing in humans. The physiological mechanism by which this effect operates is probably higher mortality rates for male embryos and fetuses as a result of nutritional deficiencies and associated stressors.

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“…A number of investigations show that the most likely influences are race and birth order, and possibly socioeconomic status and coital frequency (Teitelbaum, 1970(Teitelbaum, , 1972Peitelbaum & Mantel, 1971;James, 1983James, , 1984a.…”

Section: Introductionmentioning

confidence: 98%