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A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

The differences between the two measurements are explained by the use of different tools. However, more consistent measurements were possible using the images of 3D reconstructed bone models. Therefore, 3D measurement can be a good alternative to measurement using 2D slice images.

People vary in the extent to which they embrace their society’s traditions, impacting a range of social and political phenomena. People also vary in the degree to which they perceive disparate dangers as salient and necessitating a response. Over evolutionary time, traditions likely regularly offered direct and indirect avenues for addressing hazards; consequently, via multiple possible pathways, orientations toward tradition and toward danger may have become associated. Emerging research documents connections between individual differences in traditionalism and variation in threat responsivity in general, and pathogen-avoidance motivations in particular. Importantly, because threat-mitigating behaviors can conflict with competing priorities, the precise associations between traditionalism and pathogen avoidance likely depend on contextually contingent costs and benefits. The COVID-19 pandemic requires individuals to make decisions about consequential and costly pathogen-avoidance behaviors that can clash with other priorities. The pandemic therefore provides a real-world setting in which to test the posited relationship between traditionalism and pathogen avoidance across socio-political contexts. Across 27 societies (N = 7,844), we find that costly COVID-19-avoidance behaviors positively correlate with greater endorsement of traditional norms and values in a majority of countries. Accounting for the conflict that arises in some societies between public health precautions and competing priorities, such as the exercise of personal liberties, reveals a consistent relationship between traditionalism and COVID-19 precautions across an even wider range of social and cultural contexts. These findings support the thesis that traditionalism is associated with an enhanced tendency to attend to hazards.

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