Height and sexual dimorphism of stature among human societies

In this study, which is concerned with the varying degrees of sexual dimorphism of stature between human societies, adult male and female height measurements and male-female height ratios – the measure of sexual dimorphism – from 216 societies are statistically compared with several variables: marriage practices, protein availability, the presence of milking herds, settlement size, and climate. Our results indicate that while greater mean male height is associated with polygynous marriage, marriage practices did not exert an influence on the degree of sexual dimorphism of stature. On the other hand, the results suggest that while sexual dimorphism in height has a strong genetic component, dietary factors can influence the degree of dimorphism.     

The decline in BMI among Japanese women after World War II

The body mass index (BMI) of the Japanese is significantly lower than is found in other high-income countries. Moreover, the average BMI of Japanese women is lower than that of Japanese men, and the age-specific BMI of Japanese women has decreased over time. The average BMI of Japanese women at age 25 decreased from 21.8 in 1948 to 20.4 in 2010 whereas that of men increased from 21.4 to 22.3 over the same period. We examine the long-term BMI trend in Japan by combining several historical data sources spanning eleven decades, from 1901 to 2012, to determine not only when but also how the BMI decline among women began: whether its inception was period-specific or cohort-specific. Our nonparametric regression analysis generated five findings. First, the BMI of Japanese women peaked with the 1930s birth cohort. This means that the trend is cohort-specific. Second, the BMI of men outpaced that of women in the next cohort. Third, the BMI of Japanese children, boys and girls alike, increased steadily throughout the 20th century. Fourth, the gender difference in the BMI trend is due to a gender difference in the weight trend, not the height trend. Fifth, these BMI trends are observed in urban and rural populations alike. We conclude that the BMI decline among Japanese women began with those who were in their late teens shortly after World War II.     

When do meadow vipers (Vipera ursinii) become sexually dimorphic? – ontogenetic patterns of sexual size dimorphisms

Contrary to an increasing number of papers that document sexual dimorphism in size (and/or shape) in adults, studies dealing with sex differences in newborn and juvenile snakes are surprisingly scarce. Data about ontogenetic shifts in sexual dimorphism are generally lacking and hence, it is unclear whether sex differences are set at birth or arise post‐natally. In this study, we analyzed patterns of sexual dimorphism in body size, head dimensions and tail length (TL) among newborn, subadult and adult meadow vipers (Vipera ursinii) from the Bjelasica Mt. in Montenegro. Patterns of sexual size dimorphisms differed among traits. There was no significant difference in head dimension of males and females, but adult snakes were sexually dimorphic in body size. Sexual differences in TL were evident since birth but changed in degree throughout ontogeny. Neonate meadow vipers presented highly significant inter‐litter variation in the sexual dimorphism of all traits we have measured. Such family effects may have an important influence on extent of inter‐sexual differences in snakes and should be included in analyses of sexual dimorphism.     

The relationship between early-life conditions in the home country and adult outcomes among child immigrants in the United States

We examine the impact of health and economic conditions at birth on the adult outcomes of child immigrants using the Children of Immigrants Longitudinal Study. Our sample consists of children from 39 countries who were brought to the United States before the age of 13. We estimate immigrant outcomes as a function of the infant mortality rate (IMR) and GDP per capita of their home country in the year of birth, controlling for birth-year, year-of-arrival and country-of-birth fixed effects, as well as demographic characteristics. IMR has a significant negative impact on English reading ability and GPA in middle school. IMR significantly decreases first job prestige, years of schooling, working hours and log earnings. Some of these effects appear to be working through the lower middle school GPA. IMR does not influence self-rated health or labor market participation in adulthood, and there is no statistically significant relationship between GDP per capita and adult outcomes. Detrimental effects of IMR are significantly lower for children who arrived younger and whose parents have high school degree or above. Our estimates are of economic significance: the impact of being born in 1975 versus 1976 in Nicaragua in terms of the impact of IMR on earnings is equal to the gender effect on earnings. Our results cannot be explained by selection on observables: the pre-migration characteristics of children and parents are not associated significantly with the health and economic conditions at birth. Also, several tests show that our results cannot be explained by potential selection on unobservables.     

Sexual dimorphism and allometry in primate ossa coxae

Five measurements were taken on the ossa coxae of 454 adult primates representing Ceboidea, Cercopithecoidea and Hominoidea. Sex differences in these variables and their relationships to overall body size and sexual dimorphism were tested by means of Student's t-test and regression analysis. The study attempts to clarify the nature of primate pelvic sexual dimorphism, including allometric effects, and more specifically, test the assertion made by Mobb and Wood (1977) that sexual dimorphism in body size in not an important determinant in pelvic sex differences. Variables that contribute to the size of the birth canal tend to be larger in females than males in all taxa studied except two. In these, Hylobates and Alouatta, there were no significant differences between the sexes for any of the five variables. In general, sexual dimorphism in variables contributing to the size of the birth canal was correlated (r ? 0.8) with sexual dimorphism in body size. Furthermore, the coefficients of allometry underlying pelvic sex differences were shown to be moderately correlated (r ? 0.5) with sexual dimorphism in size. The influence of other adaptive factors on primate pelvic sexual dimorphism are also briefly discussed.     

Effects of grandmothers' smoking in pregnancy on birth weight: intergenerational cohort study

Objective To investigate the influences on birth weight of maternal smoking during pregnancy across generations.Design Intergenerational cohort study.Participants Members of the 1958 birth cohort and their offspring and mothers.Setting England, Scotland, and Wales.Main outcome measure Birth weight.Results Information on grandmothers'' smoking during pregnancy was available for 9028 singleton offspring of 4302 female cohort members. Assuming heritable transmission through the intergenerational association, grandmothers'' smoking was predicted to result in a 34 g reduction (95% confidence interval -41 g to -28 g) in the birth weight of grandchildren. Random effects models showed a negative association between grandmothers'' smoking and birth weight of grandchildren (β regression coefficient -24 g, -50 g to 3 g), but this effect was eliminated after adjustment for maternal smoking (0 g, -26 g to 26 g).No association was evident among the offspring of non-smoking mothers (n = 6105; 14 g, -17 g to 46 g), and after adjustment for maternal birth weight, adult height and body mass index, grandmothers'' smoking was positively associated with the birth weight of grandchildren (45 g, 10 g to 80 g).Conclusion Deficits in mothers'' birth weight attributable to their mother smoking was not evident in the grandchildren.     

Floral morphometrics and the evolution of sexual dimorphism in Lycium (Solanaceae)

Plants of Lycium californicum, L. exsertum, and L. fremontii produce flowers that are either male-sterile (female) or hermaphroditic, and populations are morphologically gynodioecious. As is commonly found in gynodioecious species, flowers on female plants are smaller than those on hermaphrodites for a number of floral traits. Floral size dimorphism has often been hypothesized to be the result of either a reduction in female flower size that allows reallocation to greater fruit and seed production, or an increase in hermaphroditic flower size due to the increased importance of pollinator attraction and pollen export for hermaphroditic flowers. We provide a test of these two alternatives by measuring 11 floral characters in eight species of Lycium and using a phylogeny to reconstruct the floral size shifts associated with the evolution of gender dimorphism. Our analyses suggest that female flowers are reduced in size relative to the ancestral condition, whereas flowers on hermaphrodites have changed only slightly in size. Female and hermaphroditic flowers have also diverged both from one another and from ancestral cosexual species in several shape characteristics. We expected sexual dimorphism to be similar among the three dimorphic taxa, as gender dimorphism evolved only a single time in the ancestor of the American dimorphic lineage. While the floral sexual dimorphism is broadly similar among the three dimorphic species, there are some species-specific differences. For example, L. exsertum has the greatest floral size dimorphism, whereas L. fremontii had the greatest size-independent dimorphism in pistil characters. To determine the degree to which phylogenetic uncertainty affected reconstruction of ancestral character states, we performed a sensitivity analysis by reconstructing ancestral character states on alternative topologies. We argue that investigations such as this one, that examine floral evolution from an explicitly phylogenetic perspective, provide new insights into the study of the evolution of floral sexual dimorphism.     

Sexual dimorphism in northern temperate spiders: implications for the differential mortality model

We examined sexual size dimorphism in 627 species from 123 genera and 32 families of northern temperate spiders from Great Britain and Ireland with different life histories, using phylogenetically independent contrasts. Web-building and non-web-building, sit-and-wait predators were compared with non-web-building, active hunting spiders. After accounting for phylogenetic effects, we find no evidence of differences in sexual size dimorphism in northern temperate spiders with differing life history/predatory strategies. We discuss the implications of our findings for the generality of the differential mortality hypothesis (Vollrath & Parker, 1992) with respect to spiders with different predatory modes from different habitats and environments. This recent theory proposed that extreme sexual dimorphism in spiders resulted from differential adult mortality as a consequence of different adult life histories. We conclude that this model cannot explain the less extreme dimorphism found in temperate spiders.     

Factors influencing the degree of sexual size dimorphism within and among calanoid copepod species

Populations of Diaptomus leptopus (Copepoda: Calanoida) and other calanoid copepods exhibit varying degrees of sexual size dimorphism. We examined whether intraspecific or interspecific variation in dimorphism could be explained by allometry, and we examined the relationship between adult size attained and development rate to determine any relationship between the two. We compared the degree of sexual size dimorphism in D. leptopus and in other calanoid copepods inhabiting temporary and permanent habitats. Allometry did not explain variation in sexual size dimorphism within or among populations or among species. Permanence of habitat affected the degree of dimorphism: dimorphism was greater within and among species inhabiting temporary environments. Non-significant differences in development rate were found among populations and significant differences were found between sexes of D. leptopus when reared under identical laboratory conditions: males developed more rapidly than females but there was no general relationship between development rate and adult size. Potential adaptive hypotheses to explain the differences between populations inhabiting temporary and permanent habitats are discussed.     

The health transition and biological living standards: Adult height and mortality in 20th-century Spain

This paper seeks new insights concerning the health transition in 20th century Spain by analyzing both traditional (mortality-based) and alternative (anthropometric-based) health indicators. Data were drawn from national censuses, vital and cause-of-death statistics and seven National Health Surveys dating from 1987 to 2006 (almost 100,000 subjects aged 20–79 were used to compute cohort height averages). A multivariate regression analysis was performed on infant mortality and economic/historical dummy variables.Our results agree with the general timing of the health transition process in Spain as has been described to date insofar as we document that there was a rapid improvement of sanitary and health care related factors during the second half of the 20th century reflected by a steady decline in infant mortality and increase in adult height. However, the association between adult height and infant mortality turned out to be not linear. In addition, remarkable gender differences emerged: mean height increased continuously for male cohorts born after 1940 but meaningful improvements in height among female cohorts was not attained until the late 1950s.     

Sex-specific trait architecture in a spider with sexual size dimorphism

Sexual dimorphism, or sex-specific trait expression, may evolve when selection favours different optima for the same trait between sexes, that is, under antagonistic selection. Intra-locus sexual conflict exists when the sexually dimorphic trait under antagonistic selection is based on genes shared between sexes. A common assumption is that the presence of sexual-size dimorphism (SSD) indicates that sexual conflict has been, at least partly, resolved via decoupling of the trait architecture between sexes. However, whether and how decoupling of the trait architecture between sexes has been realized often remains unknown. We tested for differences in architecture of adult body size between sexes in a species with extreme SSD, the African hermit spider (Nephilingis cruentata), where adult female body size greatly exceeds that of males. Specifically, we estimated the sex-specific importance of genetic and maternal effects on adult body size among individuals that we laboratory-reared for up to eight generations. Quantitative genetic model estimates indicated that size variation in females is to a larger extent explained by direct genetic effects than by maternal effects, but in males to a larger extent by maternal than by genetic effects. We conclude that this sex-specific body-size architecture enables body-size evolution to proceed much more independently than under a common architecture to both sexes.     

The association of adolescent socioeconomic position and adult height: Variation across racial/ethnic groups

Numerous studies have demonstrated the association of childhood socioeconomic position and adult height. Many have suggested the use of adult height as a marker of overall childhood well-being. However, few studies have examined the relationship between child/adolescent socioeconomic position and adult height in a racially/ethnically diverse cohort. Using the National Longitudinal Study of Adolescent Health, we examined the association of child/adolescent SEP (maternal education and maternal report of household income) and measured adult height in a diverse cohort of US adolescents/young adults. We found a positive gradient effect of maternal education on height in the overall population and in White and Mixed race males and females; no such gradient existed in Hispanic, Asian, or Black males or females. Only in Mixed race females was household income positively associated with height. These findings emphasize the need to recognize differential effects of socioeconomic status on height in different racial/ethnic and gender subpopulations.     

Kin and birth order effects on male child mortality: three East Asian populations, 1716–1945

Human child survival depends on adult investment, typically from parents. However, in spite of recent research advances on kin influence and birth order effects on human infant and child mortality, studies that directly examine the interaction of kin context and birth order on sibling differences in child mortality are still rare. Our study supplements this literature with new findings from large-scale individual-level panel data for three East Asian historical populations from northeast China (1789–1909), northeast Japan (1716–1870), and north Taiwan (1906–1945), where preference for sons and first-borns is common. We examine and compare male child mortality risks by presence/absence of co-resident parents, grandparents, and other kin, as well as their interaction effects with birth order. We apply discrete-time event-history analysis on over 172,000 observations of 69,125 boys aged 1–9 years old. We find that in all three populations, while the presence of parents is important for child survival, it is more beneficial to first/early-borns than to later-borns. Effects of other co-resident kin are however null or inconsistent between populations. Our findings underscore the importance of birth order in understanding how differential parental investment may produce child survival differentials between siblings.     

Quantitative genetics of costly neonatal sexual size dimorphism in squirrel monkeys (Saimiri boliviensis)

Offspring size is often an intimate link between the fitness of parents and offspring. Among mammals, neonate mass is also related to adult levels of dimorphism and intrasexual competitive mating. We describe the sex‐specific genetic architecture of neonate mass in captive squirrel monkeys (Saimiri boliviensis), a small Neotropical primate. Best fitting quantitative genetic models show strong maternal genetic effects with little difference between sexes offering limited opportunity for neonatal dimorphism to respond to observed or hypothetical selection. Heritabilities that are approximately zero also imply it is unlikely that neonatal dimorphism can evolve as a correlated response to selection on adult size. However, male mass is also more dependent on maternal condition (age and parity) making dimorphism plastic. Finally, we hypothesize that large maternal genetic effects reflect income breeding and tightly synchronized seasonal reproduction in squirrel monkeys, both of which require strong maternal control of offspring growth and timing of birth.     

Causes of sex‐biased adult survival in ungulates: sexual size dimorphism,mating tactic or environment harshness?

Using both a conventional and a phylogenetic approach, we tested whether sexual size dimorphism, mating tactic and environmental conditions influenced the between-sex differences in adult survival among 26 populations of polygynous ungulates. As a general rule, male survival was both lower and more variable among species than female survival. Whatever the method we used, sexual size dimorphism had no direct influence on male-biased mortality. In food-limited environments, the survival of males relative to that of females was lower than in good environments, suggesting a cost of large size for males facing harsh conditions. On the other hand, the survival of males relative to that of females tended to increase with sexual size dimorphism in good environments, indicating that large size may be profitable for males facing favourable conditions. Lastly, we found that the between-sex differences in adult survival did not vary with sexual size dimorphism in harem-holding or tending species, but tended to increase with sexual size dimorphism in territorial species. Our analyses indicate that sexual size dimorphism does not lead directly to a decrease in male survival compared to that of females. Thus, environmental conditions rather than the species considered could shape between-sex differences in adult survival observed in ungulate populations.     

SEXUAL SIZE DIMORPHISM AS A CORRELATED RESPONSE TO SELECTION ON BODY SIZE: AN EMPIRICAL TEST OF THE QUANTITATIVE GENETIC MODEL

We artificially selected for body size in Drosophila melanogaster to test Lande's quantitative genetic model for the evolution of sexual size dimorphism. Thorax width was used as an estimator of body size. Selection was maintained for 21 generations in both directions on males only, females only, or both sexes simultaneously. The correlated response of sexual size dimorphism in each selection regime was compared to the response predicted by four variants of the model, each of which differed only in assumptions about input parameters. Body size responded well to selection, but the correlated response of sexual size dimorphism was weaker than that predicted by any of the variants. Dimorphism decreased in most selection lines, contrary to the model predictions. We suggest that selection on body size acts primarily on growth trajectories. Changes in dimorphism are caused by the fact that male and female growth trajectories are not parallel and termination of growth at different points along the curves results in dimorphism levels that are difficult to predict without detailed knowledge of growth parameters. This may also explain many of the inconsistent results in dimorphism changes seen in earlier selection experiments.     

Long‐lived and heavier females give birth earlier in roe deer

In seasonal environments, parturition of most vertebrates generally occurs within a short time‐window each year. This synchrony is generally interpreted as being adaptive, as early born young survive better over the critical season than late born young. Among large herbivores, the factors involved in driving among‐ and within‐individual variation in parturition date are poorly understood. We explored this question by analyzing the relative importance of attributes linked to female quality (longevity, median adult body mass and cohort), time‐dependent attributes linked to female condition (reproductive success the previous year, relative annual body mass and offspring cohort (year)), and age in shaping observed variation in parturition date of roe deer. A measure of quality combining the effects of female longevity and median adult body mass accounted for 11% of the observed among‐individual variation in parturition date. Females of 2 yr old give birth 5 d later than older females. Our study demonstrates that high quality (heavy and long‐lived) females give birth earlier than low quality females. Temporally variable attributes linked to female condition, such as reproductive success in the previous year and relative annual body mass, had no detectable influence on parturition date. We conclude that parturition date, a crucial determinant of reproductive success, is shaped by attributes linked to female quality rather than by time‐dependent attributes linked to female condition in income breeders (individuals that rely on current resource intake rather than on accumulated body reserves to offset the increased energy requirements due to reproduction) such as roe deer.     

Season of birth affects short- and long-term survival

Recent research findings have highlighted the importance of early life conditions as risk factors for adult diseases and therefore determinants of subsequent survival. Given that individuals born during different seasons in seasonal environments experience different early-developmental conditions, an analysis of the effects of the season of birth on survival is considered an effective approach in clarifying the influence of early life conditions on survival in later life. In the present study, we analyzed the long-term effects of early developmental conditions in a historical population in which both nutritional levels and the burden of infectious diseases showed a seasonal variation. Using a semi-computerized linkage process, we were able to match birth and death data for 4,646 individuals born between 1634 and 1870 in the village of Es Mercadal (Minorca Island, Spain). To determine ecological differences associated with the season of birth, we first evaluated the association between season of birth and early life survival. This analysis helped us to determine seasonal variations in early life conditions such as infectious burden and nutritional levels. The season of birth had a significant effect on long-term survival in the birth cohort 1800-1870: summer births had a lower risk of death after age 15. We explain these results in terms of lower susceptibility to degenerative diseases in adult years due to superior in utero nutrition for summer births. These findings support the fetal origin hypothesis which states that the early life environment plays a key role in shaping the subsequent phenotype and risk of adult disease.