American journal of human biology : the official journal of the Human Biology Council
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1975 marked the end of a 20-year period of human biology research on physical environment. The focus then shifted from climatic adaptation to problems of nutrition, disease, and stress. However, many questions about human environmental patterns, especially in reference to their evolution, were abandoned rather than resolved. ⋯ Contrasts in environmental behaviors when comparing northern cultures such as Inuit, Athabaskan, and Norse are particularly instructive. Adaptations to life in the cold may ultimately reveal their secrets through biocultural research design modeling of environmental research. With both practical and theoretical gains still wide open, the field needs renewed attention from human biology.
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Comparative Study
Catch-up reproductive maturation in rural Tonga girls, Zambia?
To compare the timing of reproductive maturation among urban and rural Tonga girls in Zambia, anthropometric measures and Tanner stages of breast development were obtained. Subjects were 774 (282 rural, 492 urban) girls ages 6-18. Results indicate that rural girls are shorter and have smaller triceps and subscapular skinfolds than their urban counterparts. ⋯ These results suggest that rural girls progress through puberty more rapidly than the urban girls despite their later start. This finding of maturational catch-up contrasts with earlier urban/rural comparisons of girls as well as previous results among Gwembe boys, for which later pubertal onset is associated with longer duration of pubertal maturation. While the mechanism remains unclear, biocultural explanations suggest preferential feeding during adolescence as a source for rural girl's maturational catch-up.
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A fundamental evolutionary problem faced by organisms is how to allocate energy to somatic and reproductive functions in ways that optimize fitness. Given that energy is limited in all environments, energy allocation necessarily involves physiological tradeoffs between such factors as growth and reproduction, reproduction and condition, and current reproduction and future survival. Ultimately, the "decisions" that are made about energy allocation among growth, survival, and reproduction determine life history patterns and trajectories of organisms. ⋯ The results corroborate predictions from life history theory and have applied public health implications. In particular, It is suggested that policies such as lactation advocacy that encourage enhanced energy allocation to reproduction in order to promote child health may have the unintended result of compromising maternal well-being, particularly in nations of the developing world. Consequently, it is recommended that nutritional support of mothers be implemented in concert with lactation promotion.
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Thicknesses of subcutaneous fat tissue at 13 sites (triceps, biceps, forearm, subscapular, abdomen, suprailiac, axilla, chest, quadriceps, suprapatellar, hamstrings, posterior calf, medial calf), and muscle tissue at nine sites (triceps, biceps, forearm, subscapular, abdomen, quadriceps, suprapatellar, hamstrings, posterior calf) were determined by using the B-mode ultrasound technique. Subjects were 36 young (18-29 years) and 44 middle-aged women (45-64 years). Body density averaged 1.047 ± 0.007 g · ml-1 (SD) for the young, and 1.022 ± 0.005 g · ml-1 for the middle-aged women. ⋯ J. Hum. Biol. 9:247-255, 1997. © 1997 Wiley-Liss, Inc.
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There are two main questions about the sequence of emergence of the permanent teeth in humans: 1) Why is there so much variation in sequence within human populations? (2) What is the adaptive or evolutionary significance of emergence sequence? Here, the human condition is considered by comparing us to other living primates and to our evolutionary past and considered in the light of Schultz's hypothesis that sequence of tooth emergence is adapted to rate of postnatal growth (Schultz AH. In JM Tanner (ed.) Human Growth, pp 1-20, 1960). Frequencies of individual pairwise sequences (e.g., M1 I1 vs. ⋯ Trends observed across these catarrhine primates suggest that sequence and variability in sequence can be understood by a simple model of adaptation of tooth emergence to growth rate. As rate of postnatal growth slows, molars drift to later positions in sequence, either by always emerging late in sequence, or by varying in the direction of late emergence. "Augmented sequences" (sequences written with notations about variability) are important in recognizing evolutionary trends; further, they often alter perception of similarities and differences among taxa. Although samples are small, Australopithecus africanus resembles the rapidly developing genera Macaca and Pan more than it resembles Homo sapiens. © 1994 Wiley-Liss, Inc.