Hypotheses on the stability and variation of human sex ratios at birth

James, William H.

doi:10.1016/j.jtbi.2012.06.038

Cited by 36 publications

(39 citation statements)

References 44 publications

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“…This echoes findings from a smaller, survey-based sample in which a lower sex-ratio was found among mothers who did not live with a male partner before conception (Norberg 2004). However, the findings of the literature taken as a whole are mixed (Lazarus (2002);Grant (2009);James (2012)). …”

Section: Stressorssupporting

confidence: 71%

Civil conflict, gender-specific fetal loss, and selection: A new test of the Trivers–Willard hypothesis

Valente

2015

Journal of Health Economics

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A sizeable economics literature explores the effect of prenatal shocks on later health or socioeconomic status. Work in other disciplines, following the seminal contribution of Trivers & Willard (1973), suggests that prenatal shocks may increase fetal loss and reduce the number of boys relative to girls at birth. This has been largely ignored in the economics literature and could affect the interpretation of estimates of the effect of prenatal shocks and that of gender in other applied economics contexts. This paper analyzes the effect of in utero exposure to a shock -civil conflict in Nepal -on (i) fetal loss, and (ii) gender and (iii) health at birth. Maternal fixed effects estimates show that exposed pregnancies are more likely to result in a miscarriage and in a female birth, but exposed newborns are neither smaller nor more subject to neonatal mortality.JEL codes: I10, J13, O15

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Section: Stressorssupporting

confidence: 71%

Civil conflict, gender-specific fetal loss, and selection: A new test of the Trivers–Willard hypothesis

Valente

2015

Journal of Health Economics

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“…There are some suggestions in the literature that include the hormonal status of the parents at the time of conception, differential characteristics and sensibility of sperm of one sex, combination and presence of specific toxic substances (PAH, dioxin) 27 28. Although we have not evaluated the elemental composition of PM 10 , previous studies have characterised the composition of these particles from São Paulo city.…”

Section: Discussionmentioning

confidence: 98%

Follow-up of the air pollution and the human male-to-female ratio analysis in São Paulo, Brazil: a times series study

et al. 2013

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ObjectivesIn order to assess if ambient air pollution in urban areas could be related to alterations in male/female ratio this study objectives to evaluate changes in ambient particulate matter (PM10) concentrations after implementation of pollution control programmes in São Paulo city and the secondary sex ratio (SRR).Design and methodsA time series study was conducted. São Paulo’s districts were stratified according to the PM10 concentrations levels and were used as a marker of overall air pollution. The male ratio was chosen to represent the secondary sex ratio (SSR=total male birth/total births). The SSR data from each area was analysed according to the time variation and PM10 concentration areas using descriptive statistics. The strength association between annual average of PM10 concentration and SSR was performed through exponential regression, and it was adopted as a statistical significance level of p<0.05.ResultsThe exponential regression showed a negative and significant association between PM10 and SSR. SSR varied from 51.4% to 50.7% in São Paulo in the analysed period (2000–2007). Considering the PM10 average concentration in São Paulo city of 44.72 μg/m3 in the study period, the SSR decline reached almost 4.37%, equivalent to 30 934 less male births.ConclusionsAmbient levels of PM10 are negatively associated with changes in the SSR. Therefore, we can speculate that higher levels of particulate pollution could be related to increased rates of female births.

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“…Low sex ratios may arise due to a variety of other mechanisms (e.g. those that affect sex at conception) [30]. We, however, know of no other hypothesized mechanism for sex ratio variation that would predict its inverse relation with male infant mortality and LRS.…”

Section: Discussionmentioning

confidence: 99%

Culled males, infant mortality and reproductive success in a pre-industrial Finnish population

et al. 2015

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Theoretical and empirical literature asserts that the sex ratio (i.e. M/F) at birth gauges the strength of selection in utero and cohort quality of males that survive to birth. We report the first individual-level test in humans, using detailed life-history data, of the 'culled cohort' hypothesis that males born to low annual sex ratio cohorts show lower than expected infant mortality and greater than expected lifetime reproductive success. We applied time-series and structural equation methods to a unique multigenerational dataset of a natural fertility population in nineteenth century Finland. We find that, consistent with culled cohorts, a 1 s.d. decline in the annual cohort sex ratio precedes an 8% decrease in the risk of male infant mortality. Males born to lower cohort sex ratios also successfully raised 4% more offspring to reproductive age than did males born to higher cohort sex ratios. The offspring result, however, falls just outside conventional levels of statistical significance. In historical Finland, the cohort sex ratio gauges selection against males in utero and predicts male infant mortality. The reproductive success findings, however, provide weak support for an evolutionarily adaptive explanation of male culling in utero.

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Hypotheses on the stability and variation of human sex ratios at birth

Cited by 36 publications

References 44 publications

Civil conflict, gender-specific fetal loss, and selection: A new test of the Trivers–Willard hypothesis

Civil conflict, gender-specific fetal loss, and selection: A new test of the Trivers–Willard hypothesis

Follow-up of the air pollution and the human male-to-female ratio analysis in São Paulo, Brazil: a times series study

Culled males, infant mortality and reproductive success in a pre-industrial Finnish population

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