Recently, a metric approach to skeletal sex determination was published by Paiva and Segre which is based on the summation of two triangular areas defined by three distinct craniometric landmarks: Porion, Mastoidale, and Asterion. According to the authors, values for the total triangle > or =1447.40 mm(2) are characteristic for male crania, while values < or =1260.36 mm(2) are indicative of female skulls (95% confidence). In order to evaluate the method's validity, two sex- and age-documented samples of different provenience were analyzed (N=197). The results show that while the indicated measurements display significant sex differences, the technique is of little practical meaning where a single individual must be independently classified. It is hypothesized that differences in the expression of sexual dimorphism as well as a population-specific variability of the asterion location undermine the value of the mastoid triangle as a sex determinant.
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The observation that declines in the human secondary sex ratio (SSR) may be linked to stressful periconceptional periods has received considerable attention (Catalano [2003] Hum Reprod 18:1972-1975; Catalano et al. [2005] Int J Epidemiol 34:944-948, [2005] Hum Reprod 20:1221-1227, [2005] Paediatr Perinat Epidemiol 19:413-420). For the purpose of testing the external validity of this phenomenon, birth records from four German village genealogies (N = 1,048) were analyzed to study the impact of the French Revolutionary Wars (1787-1802) on the proportion of male births. All births were subdivided into three cohorts (prewar, 1787-1792; war, 1792-1797; and postwar, 1797-1802). Differences in SSR between cohorts achieved statistical significance (chi2= 7.695; df = 2; P = 0.021). In addition, changes in SSR before, during, and after the wars were monitored by risk analysis. Using the SSR of the prewar period as a control, the results of the war cohort failed to achieve statistical significance (regression coefficient, -0.257; ExpB= 0.773; P = 0.118), while the odds reduction of 32.3% in the postwar period proved to be statistically significant (regression coefficient, -0.390; ExpB= 0.677; P = 0.006). It is hypothesized that the experience of postwar economic hardship (attributable to lowered food availability paired with dietary changes) represents the most likely proximate cause. The study also finds evidence of a parental sex ratio manipulation strategy meant to offset the female-biased SSR after the wars. It is argued that from an evolutionary perspective both the decline in SSR in response to stress as well as parental manipulation of the tertiary sex ratio convey reproductive advantages.
The present research investigates the moderating role of the "child factor" in impression formation. 307 university students (148 males, 159 females) were asked to assess 14 traits related to physical attractiveness, resource accruing potential, and emotional stability. The stimulus person was either accompanied by a child or shown individually. As expected, targets depicted with children were believed to be more family-committed and to possess greater parenting skills. The child factor also favourably biased respondents' assessments in terms of honesty, faithfulness, and maturity. Women with children were assumed to be less ambitious, while men with children were believed to be more generous and possess higher status and financial security. All results are discussed within the greater evolutionary context of kin selection and the "good-parent process". It is hypothesized that the negative stereotyping of the voluntary childfree is a by-product of cues that infer prosocial behaviour--similar to those used in mate selection.
According to recent studies in evolutionary anthropology, firstborn daughters influence both parity progression and sibling survival by acting as so-called helpers at the nest. Based on 534 sets of household data from family reconstitution, the current analysis fails to show that offspring sex had any direct impact on maternal fertility, sibling survivorship, birth spacing, or reproductive span. Instead, the results indicate that fertility decisions were heavily affected by proximate factors such as child mortality and gender preferences. Families who had experienced child death were swift to substitute the loss with another pregnancy--a phenomenon known as replacement strategy. Similarly, a surplus of daughters acted as a strong impulse for parity progression, not because of potential helping effects but in an attempt to conceive additional sons. This is particularly apparent when the odds of grandmultiparity are considered.
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