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Changes in body height throughout extended historic periods are very complex and dynamic processes. Thispilot study aimed to investigate the pattern of longitudinal height z-scores changes in children before and after entering kindergarten. In summer 2016, we measured height and weight of 32 children from 4 groups of two kindergartens aged 3–6 years. All ages were centered according to the age of entry into the kindergarten. For each child we determined mean z-scores for height before and after entering the kindergarten, and assessed the variances for each kindergarten group. Twenty-two children targeted in height z-scores towards average height of their respective kindergarten group, 10 children did not. Due to the small numbers, the convergence in height variance however, remained insignificant (chi-squared independence test, p = 0.127). Additional studies with larger sample sizes are needed to confirm this pilot study.
Background: There is a common perception that tall stature results in social dominance. Evidence in meerkats suggests that social dominance itself may be a strong stimulus for growth. Relative size serves as the signal for individuals to induce strategic growth adjustments. Aim: We construct a thought experiment to explore the potential consequences of the question: is stature a social signal also in humans? We hypothesize that (1) upward trends in height in the lower social strata are perceived as social challenges yielding similar though attenuated upward trends in the dominant strata, and that (2) democratization, but also periods of political turmoil that facilitate upward mobility of the lower strata, are accompanied by upward trends in height. Material and methods: We reanalyzed large sets of height data of European conscripts born between 1856-1860 and 1976-1980; and annual data of German military conscripts, born between 1965 and 1985, with information on height and school education. Results: Taller stature is associated with higher socioeconomic status. Historic populations show larger height differences between social strata that tend to diminish in the more recent populations. German height data suggest that both democratization, and periods of political turmoil facilitating upward mobility of the lower social strata are accompanied by a general upward height spiral that captures the whole population. Discussion: We consider stature as a signal. Nutrition, health, general living conditions and care giving are essential prerequisites for growth, yet not to maximize stature, but to allow for its function as a lifelong social signal. Considering stature as a social signal provides an elegant explanation of the rapid height adjustments observed in migrants, of the hitherto unexplained clustering of body height in modern and historic cohorts of military conscripts, and of the parallelism between changes in political conditions, and secular trends in adult human height since the 19th century.
The anatomically modern human Homo sapiens sapiens is distinguished by a high adaptability in physiology, physique and behaviour in short term changing environmental conditions. Since our environmental factors are constantly changing because of anthropogenic influences, the question arises as to how far we have an impact on the human phenotype in the very sensitive growth phase in children and adolescents. Growth and development of all children and adolescents follow a universal and typical pattern. This pattern has evolved as the result of trade-offs in the 6-7 million years of human evolution. This typically human growth pattern differs from that of other long-living social primate species. It can be divided into different biological age stages, with specific biological, cognitive and socio-cultural signs. Phenotypic plasticity is the ability of an organism to react to an internal or external environmental input with a change in the form, state, and movement rate of activity (West-Eberhard 2003). The plasticity becomes visible and measurable particularly when, in addition to the normal variability of the phenotypic characteristics within a population, the manifestation of this plasticity changes within a relatively short time. The focus of the present work is the comparison of age-specific dimensional changes. The basic of the presented studies are more than 75,000 anthropometric data-sets of children and adolescence from 1980 up today and historical data of height available in scientific literature. Due to reduced daily physical activity, today's 6-18 year-olds have lower values of pelvic and elbow breadths. The observed increase in body height can be explained by hierarchies in social networks of human societies, contrary to earlier explanations (influence of nutrition, good living conditions and genetics). A shift towards a more feminine fat distribution pattern in boys and girls is parallel to the increase in chemicals in our environment that can affect the hormone system. Changing environmental conditions can have selective effects over generations so that that genotype becomes increasingly prevalent whose individuals have a higher progeny rate than other individuals in this population. Those then form the phenotype which allows optimum adaptation to the changes of the environmental conditions. Due to the slow patterns of succession and the low progeny rate (Hawkes et al. 1998), fast visible in the phenotype due to changes in the genotype of a population are unlikely to occur in the case of Homo sapiens sapiens within short time. In the data sets on which the presented investigations are based, such changes appear virtually impossible. The study periods cover 5-30 to max.100 years (based on data from the body height from historical data sets).