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The co-existence of very short stature due to poor chronic environment in early life and obesity is becoming a public health concern in rapidly transitioning populations with high levels of poverty. Individuals who have very short stature seem to be at an increased risk of obesity in times of relative caloric abundance. Increasing evidence shows that an individual is influenced by exposures in previous generations. This study assesses whether maternal poor early life environment predicts her child's adiposity using cross sectional design on Maya schoolchildren aged 7-9 and their mothers (n = 57 pairs). We compared maternal chronic early life environment (stature) with her child's adiposity (body mass index [BMI] z-score, waist circumference z-score, and percentage body fat) using multiple linear regression, controlling for the child's own environmental exposures (household sanitation and maternal parity). The research was performed in the south of Merida, Yucatan, Mexico, a low socioeconomic urban area in an upper middle income country. The Maya mothers were very short, with a mean stature of 147 cm. The children had fairly high adiposity levels, with BMI and waist circumference z-scores above the reference median. Maternal stature did not significantly predict any child adiposity indicator. There does not appear to be an intergenerational component of maternal early life chronic under-nutrition on her child's obesity risk within this free living population living in poverty. These results suggest that the co-existence of very short stature and obesity appears to be primarily due to exposures and experiences within a generation rather than across generations., (Copyright © 2013 Wiley Periodicals, Inc.)

Objectives: Human growth data from Guatemalan school children were analyzed to test the hypothesis that the degree of sexual size dimorphism (SSD) in height is reduced for people living under more adverse environmental quality., Methods: The sample consists of 2,560 girls and 3,262 boys, 6-16.99 years of age, from the two major Guatemalan ethnic groups, Maya of very low socioeconomic status (SES) and Ladino of high, middle, and low SES. SES was estimated by questionnaire and ethnographic observation. All data are from the Longitudinal Study of Child Development of the Universidad del Valle de Guatemala. Significance of SSD was tested within each whole year age category (e.g., 6.0-6.9 years) by SES for Ladinos and Maya. Ethnic groups were then compared for each age category to determine whether the SSD values were significantly different between groups., Results: Statistically significant height SSD was found for 10 of the 11 age categories for the high SES Ladinos, 8 of the 11 age categories for middle SES Ladinos, 3 of the 11 low SES Ladino age categories, and 0 of the 11 very low SES Maya age categories. For all SES and ethnic groups SSD tended to decrease between 6 and 11 years of age and then increase after age 12 years., Conclusions: A poor quality environment for growth and development, as estimated by SES, was found to reduce or eliminate statistically significant SSD. Patterns of biological maturation before and after puberty also seem to contribute to age changes in SSD., (Copyright © 2013 Wiley Periodicals, Inc.)

Objectives: To test the hypothesis that leg length-relative-to-stature is a more sensitive indicator of nutrition and health than is total height (HT) or sitting height (SH) in a sample of 109 triads of urban Maya children (6.0-8.99 years), their mothers, and maternal grandmothers from Merida, Mexico., Methods: From September 2011 to June 2012, the following factors were obtained from all participants: (1) HT, SH, and leg length (LL); (2) the sitting height ratio (SHR = [SH × 100]/HT), relative leg length index (RLLI = [LL × 100]/height), and percentiles and z-scores of HT, SH, and LL were calculated; and (3) the percentages of stunting for children or very short ZHT for the adults, short ZSH, and short ZLL: HT-for-age, SH-for-age, or LL-for-age below the 5th percentile of the reference were calculated. Correlations were performed to examine the association between z-scores of HT, SH, and LL among three generations., Results: Stunting in children was 11% (short ZLL = 29%, short ZSH = 7%). Short ZHT was present in 71% of mothers (short ZLL = 54%, short ZSH = 50%) and 90% of grandmothers (short ZLL = 69%, short ZSH = 83%). Significant correlations in ZHT, ZSH, and ZLL were found in mother-to-child and grandmother-to-mother, with the strongest correlations for ZLL., Conclusions: These findings support the hypothesis for children and mothers. Based on ZLL, there is evidence that childhood and nutrition have improved somewhat for each younger generation. Persistent environmental adversity during growth resulted in growth deficits for LL and SH for the mothers and grandmothers., (Copyright © 2013 Wiley Periodicals, Inc.)

The Maya are the most populous and shortest in stature Native American ethnic group. The Maya provide us a good opportunity to study the dietetic characteristics of a group who experience nutritional dual burden (the combination of under and ovenutrition) at the individual, mother-child dyad and population level. The aim of this study is to describe general dietetic patterns of a sample of Maya mothers and children who experienced nutritional dual burden and were living in the city of Merida, Yucatan, Mexico. From February to July 2010 we applied food frequency questionnaires (FFQ) to 58 dyads of Maya mothers and their children (7-9 years old). The FFQ was developed by staff of the Department of Human Ecology at Cinvestav and included 78 foods, grouped in: cereals and tubers, foods of animal origin, leguminous vegetables, fats, fruits, vegetables, sugars, and daily products. The frequencies of consumption were classified in four levels: 1) no consumption, 2) low (1-2 days/week), 3) medium (3-4 days/week), high (5-7 days/week). The observed pattern suggests a low consumption of fruits and vegetables, a medium consumption of pork, eggs, oil and lard, and a high consumption of soda and whole milk. From these frequencies we extrapolated that the dietetic pattern is characterized by a low intake of fibre and micronutrients and high intake of fat and sugars, findings supported by previous National and regional studies. Our observations suggest that the studied group have a dietetic pattern that has moved away from a traditional Maya diet.

Based on previous findings showing both better birth outcomes in migrant than in Spanish women and different rates of medical intervention according to mother's origin, we hypothesize that mode of delivery decisions to solve similar problems differ according to ethnic origin. Ethnic differences for maternal characteristics, medical intervention, and mode of delivery were evaluated in 16,589 births from a Maternity Hospital in Madrid (Spain). Multinomial logistic regression analysis was used to evaluate the effect of mother's ethnic origin on the mode of delivery, adjusting for mother's age, parity, gestational age, birth weight, and epidural anesthesia. Compared with the Spanish mothers, the risk of having a Caesarean section is significantly higher in Latin Americans and significantly lower for the Chinese. Both low birth weight and macrosomic deliveries are at higher risk for Caesarean section. The interventionist system characterizing Spain is being extended to all ethnic groups and, at the same time, different medical interventions are applied to similar problems depending on women's ethnic origin. Obstetric interventions might be contributing to the increasing trend of low birth weight and late preterm/early full term deliveries (37-38 weeks) observed in Spain. Behavioral and cultural values of the women and of the health care providers may contribute to systematic differences in labor management and mode of delivery.

This essay provides a brief history of the etymology and usage of the phrase 'secular change' followed by a description of secular changes in height and relative leg length in childhood, adolescence, and adulthood. Both positive and negative changes are described. Possible causes are reviewed, with an emphasis on nutrition, infection and social-economic-political (SEP) environments. The case of the Maya people living in Mexico, Guatemala, and the United States is given, which shows that intergenerational changes in stature and its components - leg length and upper body length - may occur in different directions and at different rates. The deleterious consequences of rapid catch-up growth after birth have been proposed as a hypothesis to explain the 150 years of positive secular change in height of populations in the richer nations. That hypothesis is found to be an incomplete explanation. Growth changes better track the rate of change in SEP factors. Epigenetic assimilation is a new hypothesis, which focuses on those epigenetic processes regulating gene expression, metabolic function, physiology, and behavior. Epigenetic assimilation shows promise to account for plasticity and intergenerational changes in human growth and development phenotypes., (Copyright © 2013 Nestec Ltd., Vevey/S. Karger AG, Basel.)

Background: Childhood stunting has been associated with an increased risk of obesity in adulthood, but the causes are unclear. This study hypothesizes that stunting significantly reduces both resting and activity energy expenditure., Aim: To assess and describe energy expenditure of low socio-economic Maya children and to determine whether stunting is independently related to energy expenditure after controlling for lean mass., Subjects and Methods: Thirty-three urban Maya children, 17 boys, aged 7-9 years, living in Merida, Mexico, were measured for height, weight and bioelectrical impedance analysis (BIA). Body composition was estimated from BIA. Energy expenditure was measured for one week using the Actiheart (combined heart rate and accelerometer)., Results: Stunting (height-for-age below the 5(th) percentile of NHANES III based references) affected 35% of these physically active children. Using multiple linear regression analysis, greater lean body mass predicted higher resting and activity energy expenditure. Stature was not a significant predictor of resting energy expenditure. A lower height-for-age z-score, but not stunting as a categorical variable, significantly predicted lower activity energy expenditure., Conclusion: The hypothesis that stunting reduces total energy expenditure (resting + active) in children is not supported. Rather, children with shorter stature and less lean body mass have lower total energy expenditure. Complex interactions between body size, body composition, and metabolic activity appear to elevate the risk for later life obesity in these Maya children.

Previous research links both low birth weight (LBW) and relative leg length (RLL) to a similar set of adult pathologies, including type II diabetes, coronary vascular disease, and some cancers. Historically, LBW has been frequently used as a broad indicator of the quality of the intrauterine environment, while RLL has been considered a sensitive measure of childhood environmental quality. While these observations have been taken to suggest that these measures reflect independent exposures at different life-stages, their mutual association with a similar set of later pathologies makes this assumption less certain than it may have previously seemed. Nationally representative data from the Third National Health and Nutrition Examination Survey (NHANES III) are used to test the hypothesis that LBW predicts reductions in the development of leg length relative to stature. After controls for important socioeconomic exposures that might confound measurement of such a relationship, we find statistical and biological evidence that variation in birth weight and variation in the development of leg length relative to stature (RLL) are independent. The results suggest that these two measures may represent independent information on prenatal and postnatal environmental quality., (Copyright © 2012 Wiley Periodicals, Inc.)

Objective: To understand age-sex variation of stature and upper arm length (UAL) and to estimate stature from UAL through prediction equations., Methods: A cross-sectional study was undertaken in 2006-2007 among 458 children (218 boys and 240 girls) aged 4.0 to 6.92 y of south Merida in Yucatan, Mexico., Results: The results show significant age variation (p < 0.001) of stature and upper arm length (UAL) in children. Boys show significantly higher mean stature and UAL compared to the girls. Relative proportion of upper arm length to stature is greater in boys. Interrelationship between stature and upper arm length exhibits significant association with respect to age and sex of children. Reconstruction of stature from upper arm length through regression analysis also gives good prediction models for separate and combined samples of both sexes with age. Regression coefficients for UAL predicting stature account for 0.90 or greater variance in the dependent variable (stature). The difference between reconstructed stature and the actual measurement is less than ±2.00 cm., Conclusions: UAL appears to be a reliable indicator to estimate stature in children aged 4.0 to 6.92 y old.

This paper focuses on the phenomenon of the nutritional dual-burden in the developing world. Nutritional dual-burden is defined as the coexistence of under-and-over nutrition in the same population/group, the same household/family, or the same person. In this paper we aim: a) to describe the different types of nutritional dual-burden, b) to identify the anthropometric indicators generally used to classify the nutritional dual-burden, c) to focus our attention on a dual-burden group (the Maya from Merida, Yucatan, Mexico), d) to illustrate problems in the categorization of the dual-burden, and e) to suggest possible health implications. Our results show that, for our sample, the prevalence of individual dual-burden among children is very low, but is very high among the mothers and for mother-child pairs (household dual-burden). Most importantly, the criteria used to assess the nutritional status of the individuals and of the families will play an important role in the estimated prevalence of nutritional dual-burden, and this will have practical impacts for health intervention programs.

In 1835, Edouard Mallet published a notable but today nearly forgotten study of the average height of Genevan conscripts. His individual data included 3029 conscripts born between 1805 and 1814, examined and measured between 1826 and 1835. Mallet's work was only the third auxological study to be based on a large sample of individual conscript data, the other two being those of Louis-René Villermé and Adolphe Quetelet, but as far as we know Mallet's was the first to note the law of normal distribution. Like Villermé and Quetelet, Mallet explained urban/rural and international differences in average height strictly in terms of environmental and economic determinants. In the recent past, references to Mallet's work have been rare, and limited to citations of his computed averages. We postulate that Mallet and his study deserve greater consideration for their contribution to the field of anthropometric history than they have yet received., (2011 Elsevier B.V. All rights reserved.)

Objectives: Body mass index (BMI) is used frequently to estimate adiposity levels in children and adults. However, the applicability of BMI to populations with high levels of stunting has been questioned. Stunted people can have disproportionately short legs, which may increase BMI without increasing body fat because of the relatively larger trunk compared with the legs., Methods: A sample of 57 urban Maya schoolchildren, aged 7-9 years (31 boys), and 53 adult women underwent anthropometric assessments and bioelectrical impedance analysis. Multiple linear regression was performed to determine whether the ability of BMI to predict adiposity indicators is altered by stunting and sitting height ratio (SHR). The adiposity indicators were waist circumference, sum of skinfolds, upper arm muscle area, upper arm fat area, and arm fat index., Results: BMI was the strongest predictor of all adiposity indicators and in most cases, explained more of the variance in adiposity of Maya children than Maya women. Abdominal adiposity was better predicted by BMI than peripheral adiposity in Maya women and Maya children. Stunting was significant in predicting adiposity in some models but never substantially changed the variance explained. SHR was never a significant predictor., Conclusions: The relationship between BMI and adiposity indicators is not changed by stunting status or body proportions in this short population of urban Maya children and women. BMI can be used as an indicator of adiposity for these children but not the women. It is recommended that BMI is used in conjunction with other estimates of body composition., (Copyright © 2011 Wiley-Liss, Inc.)

Logistics of using new measurement devices are important to understand when developing protocols. This paper discusses the logistics of using Actiheart physical activity monitors on children in an urban, tropical environment in a developing country. Actiheart monitoring of 36 children aged 7-9 years old was undertaken for 7 days in the city of Mérida, Yucatán, Mexico. The Actiheart proved fragile for children and difficult to mend in the field. The excessive sweating due to the tropical climate caused poor adherence of the electrode pads, requiring a pad change midway through and extra pads to be provided. Also extra time was needed to be allotted for increased instructions to participants and their mothers and for individual calibration. When collecting objectively measured physical activity data under harsh conditions, the protocol must accommodate local conditions and device limitations and allow increased time with participants to obtain good quality data., (Copyright © 2011 Wiley-Liss, Inc.)

The theme of the 2011 meetings of the German Anthropological Society, "Biological and Cultural Markers of Environmental Pressure", provides the entree to revisit one of Anthropology's most enduring canons - hunters and gathers are well-nourished and healthy. The Dobe !Kung foragers of the Kalahari Desert often serve as a model of hunter-gatherer adaptation for both extant and Paleolithic humans. A re-analysis of food intake, energy expenditure, and demographic data collected in the 1960s for the Dobe !Kung finds that their biocultural indicators of nutritional status and health were, at best, precarious and, at worst, indicative of a society in danger of extinction. Hunting and gathering is the lifestyle to which the human species was most persistently adapted, in terms of the biological, cultural, and emotional meanings of the word 'adapted.' However, the few remaining foraging groups studied in the 20th Century are unlikely to serve as the ideal models of that ancient way of life.

Decomposing stature into its major components is proving to be a useful strategy to assess the antecedents of disease, morbidity and death in adulthood. Human leg length (femur + tibia), sitting height (trunk length + head length) and their proportions, for example, (leg length/stature), or the sitting height ratio (sitting height/stature x 100), among others) are associated with epidemiological risk for overweight (fatness), coronary heart disease, diabetes, liver dysfunction and certain cancers. There is also wide support for the use of relative leg length as an indicator of the quality of the environment for growth during infancy, childhood and the juvenile years of development. Human beings follow a cephalo-caudal gradient of growth, the pattern of growth common to all mammals. A special feature of the human pattern is that between birth and puberty the legs grow relatively faster than other post-cranial body segments. For groups of children and youth, short stature due to relatively short legs (i.e., a high sitting height ratio) is generally a marker of an adverse environment. The development of human body proportions is the product of environmental x genomic interactions, although few if any specific genes are known. The HOXd and the short stature homeobox-containing gene (SHOX) are genomic regions that may be relevant to human body proportions. For example, one of the SHOX related disorders is Turner syndrome. However, research with non-pathological populations indicates that the environment is a more powerful force influencing leg length and body proportions than genes. Leg length and proportion are important in the perception of human beauty, which is often considered a sign of health and fertility.

Decomposing stature into its major components is proving to be a useful strategy to assess the antecedents of disease, morbidity and death in adulthood. Human leg length (foot + tibia + femur), sitting height (trunk length + head length) and their proportions (for example the relative leg length in proportion to stature, and the sitting height ratio [sitting height/stature x 100], among others) are used as epidemiological markers of risk for overweight (fatness), coronary heart disease, diabetes and certain cancers. There is also wide support for the use of relative leg length as an indicator of the quality of the environment for growth during infancy, childhood and the juvenile years of development. Human beings follow a cephalo-caudal gradient of growth, the pattern of growth common to all mammals. A special feature of the human pattern is that between birth and puberty the legs grow relatively faster than other post-cranial body segments. For groups of children and youth, short stature due to relatively short legs (i.e. a high sitting height ratio) is generally a marker of an adverse environment. The development of human body proportions is the product of environmental x genomic interactions, although few if any specific genes are known. The short stature homeobox-containing gene (SHOX) is the first genomic region that may be relevant to human body proportions. For example, one of the SHOX related disorders is Turner syndrome. However, in most cases research has been showing that environment is a more powerful force to shape leg length and body proportions than genes. Leg length and proportion are important in the perception of human beauty, which is often considered a sign of health and fertility. There are a variety of cosmetic, fashion, and surgical interventions to enhance perceived or actual leg length.

In developing nations, obesity has increased dramatically in the last decade, but a high prevalence of stunting still coexists. The intergenerational influences hypothesis (IIH) is one explanation for this. We test the IIH regarding variation in maternal stature, mother's age at pregnancy, and infant birth weight in relation to risk for overweight and stunting in 206 Maya children (4-6 years old) from Mérida, Yucatan, Mexico. The Maya children are compared with growth references (Frisancho 2008: Anthropometric Standards: An Interactive Nutritional Reference of Body Size and Body Composition for Children and Adults. Ann Arbor, MI: The University of Michigan Press. 335 pp) for height, weight, and body mass index (BMI). Almost 70% of the mothers are shorter than 150 cm. Mothers' height and child's birth weight predict overweight. Children with a mother shorter than 150 cm are less than half as likely (OR = 0.44) to be overweight compared to children whose mothers are equal to or taller than 150 cm. Children with birth weights below 3,000 g are only a third as likely to be overweight (OR = 0.28) than their peers within the range of normal birth weight (3,000-3,500 g). Sex of the child, mother's height, and birth weight predict stunting. Girls are only 40% as likely as boys to be stunted. Children with a mother below 150 cm are 3.6 times more likely of being stunted. Children with birth weights below 3000 g are over 3 times more likely to be stunted relative to children with birth weights within the normal range. Mother's age at pregnancy is not a predictor of overweight or stunting. Our findings conform the IIH and with similar studies of populations undergoing nutritional/epidemiological transitions from traditional to globalized lifestyles.

The grandmother hypothesis (GH) of Hawkes et al. ([1998]: Proc Natl Acad Sci USA 95: 1336-1339) finds that selection for lower adult mortality and greater longevity allow for the evolution of prolonged growth in human beings. In contrast, other researchers propose that the evolution of the human childhood and adolescent stages of life history prolonged the growth period and allowed for greater biological resilience and longevity compared with apes. In this article, the GH model is reanalyzed using new values for some of its key variables. The original GH set the age at human feeding independence at 2.8 years of age (weaning) and used demographic data from living foragers to estimate average adult lifespan after first birth at 32.9 years. The reanalysis of the GH uses age 7.0 years (end of the childhood stage) as the minimum for human feeding independence and uses data from healthier populations, rather than foragers, to derive an estimate of 48.9 years for average adult life span. Doing so finds that selection operated to first shorten the infancy stage (wean early compared with apes), then prolong the growth period, and finally result in greater longevity. The reanalysis provides a test of the reserve capacity hypothesis as part of a multilevel model of human life history evolution., (2009 Wiley-Liss, Inc.)

The growth status of Mozambique adolescents was assessed to test the hypothesis that relative leg length is a more sensitive indicator of the quality of the environment than the total height. The sample comprised 690 boys and 727 girls, aged between 9 and 17 years, from Maputo. It is divided between those living in the Centre of Maputo and those living in the slums on the periphery of the city. Height, weight, and sitting height were measured and the sitting height ratio was calculated. The hypothesis that relative leg length is more sensitive than total stature as an indicator of environmental quality is not uniformly confirmed. Overall, mean stature is greater for the centre group than the slum group, but relative leg length as measured by the sitting height ratio does not differ. Compared with African-American references (NHANES II), all centre girls, 9- to 14-year-old slum girls, all slum boys, and the oldest centre boys show relatively shorter legs. These findings show that within the Mozambique sample, relative leg length is not sensitive enough to distinguish the quality of the living environment. Mozambique was a colony of Portugal until 1975. Civil unrest and warfare characterized the late Colonial period and the postindependence period until a peace settlement was concluded in 1992. It is possible that all socioeconomic status groups within the country suffered sufficiently to reduce relative leg length compared with the better-off African-American reference sample. Possible genetic influences on relative leg length are also discussed.

Overweight and obesity have developed into major illnesses in most Western societies and significantly contribute to the financial burden of modern public health systems. Almost daily, new therapeutic proposals are published in the lay press, and also the scientific literature has increased dramatically in recent years. E.g., when searching MEDLINE (1966 - May 2008 (1)), the key word "obesity" meanwhile appears in more than 108,000 articles. Primary focus however, is put upon aspects of treatment, neglecting the role of taste and appetite regulation. Combining keywords like "obesity + treatment" results in over 50.000 citations, "obesity + diet" in over 23.000, "obesity + energy + expenditure" in over 13.000 citations (even "obesity + gastric + bypass" still evoke 2.600 citations), whereas "obesity + appetite + regulation" result in some 3.000, "obesity + NPY" - neuropeptid Y being one of the major chemical stimulators of appetite - evoke some 500 and "obesity + Arc + nucleus" - the arcuate nucleus being the anatomical centre of appetite regulation - no more than 370 scientific publications. The apparent scarcity of literature about taste and appetite regulation and the amazing lack of interest in neuronal information processing in overweight and obesity, has prompted the authors to brainstorm new aspects of the world-wide derailment of weight control.

Human beings growing-up in adverse biocultural environments, including undernutrition, exposure to infection, economic oppression/poverty, heavy workloads, high altitude, war, racism, and religious/ethnic oppression, may be stunted, have asymmetric body proportions, be wasted, be overweight, and be at greater risk for disease. One group of researchers explains this as a consequence of "developmental programming" (DP). Another group uses the phrase "predictive adaptive response" (PAR). The DP group tends to view the alterations as having permanent maladaptive effects that place people at risk for disease. The PAR group considers the alterations at two levels of adaptation: (1) "short-term adaptive responses for immediate survival" and (2) "predictive responses required to ensure postnatal survival to reproductive age." The differences between the DP and PAR hypotheses are evaluated in this article. A life history theory analysis rephrases the DP versus PAR debate from disease or adaptation to the concept of "trade-offs." Even under good conditions, the stages of human life history are replete with trade-offs for survival, productivity, and reproduction. Under adverse conditions, trade-offs result in reduced survival, poor growth, constraints on physical activity, and poor reproductive outcomes. Models of human development may need to be refined to accommodate a greater range of the biological and cultural sources of adversity as well as their independent and interactive influences., (Copyright (c) 2007 Wiley-Liss, Inc.)

Nutritional transition, urbanization, and physical inactivity are primary factors responsible for the worldwide epidemic of overweight/obesity (OW/OB). However, these factors fail to explain the epidemic of OW/OB in developing countries and in recent-migrants to developed countries. Among these, OW/OB is associated with short/stunted stature and coexists with undernutrition at much higher rates than is statistically expected. Changes in metabolic pathways toward reduced fat oxidation and increased metabolism of carbohydrate may explain, in part, this phenomenon. Also, intergenerational consequences of malnutrition and poor health of the mothers may lead to impaired phenotypes in their offspring. We propose a novel methodology to assess the history of early life malnutrition by assessing the sitting height ratio of the mothers. The degree of "short leggedness" reflects undernutrition when the mother was an infant/child. Collectively, behavioral, environmental, metabolic and intergenerational components of early life undernutrition may provide a more satisfactory explanation for later life obesity.

It has long been claimed that Homo sapiens is the only species that has language, but only recently has it been recognized that humans also have an unusual pattern of growth and development. Social mammals have two stages of pre-adult development: infancy and juvenility. Humans have two additional prolonged and pronounced life history stages: childhood, an interval of four years extending between infancy and the juvenile period that follows, and adolescence, a stage of about eight years that stretches from juvenility to adulthood. We begin by reviewing the primary biological and linguistic changes occurring in each of the four pre-adult ontogenetic stages in human life history. Then we attempt to trace the evolution of childhood and juvenility in our hominin ancestors. We propose that several different forms of selection applied in infancy and childhood; and that, in adolescence, elaborated vocal behaviors played a role in courtship and intrasexual competition, enhancing fitness and ultimately integrating performative and pragmatic skills with linguistic knowledge in a broad faculty of language. A theoretical consequence of our proposal is that fossil evidence of the uniquely human stages may be used, with other findings, to date the emergence of language. If important aspects of language cannot appear until sexual maturity, as we propose, then a second consequence is that the development of language requires the whole of modern human ontogeny. Our life history model thus offers new ways of investigating, and thinking about, the evolution, development, and ultimately the nature of human language.

The prevalence of obesity among both adults and children in the U.S. has risen to all time highs in the past two decades. We propose that an increase in the marginal rate of time preference has contributed to increasing obesity. More people are consuming more calories than they expend because they have become less willing to trade current pleasure for potential future health benefits. Accordingly, this paper explores the association between body mass index (BMI) and time preference. We use the National Longitudinal Survey of Youth (NLSY79) to test our hypothesis that time preference and BMI are positively related. We find some evidence that there is such a positive association among black and Hispanic men and black women.

It is hypothesized that recent trends in US and worldwide obesity are, in part, related to an increase in the marginal rate of time preference, where time preference refers to the rate at which people are willing to trade current benefit for future benefit. The higher the rate of time preference, the larger is the factor by which individuals discount the future health risks associated with current consumption. Data from the United States, as well as international evidence, suggest that a relationship between these two variables is plausible. The authors encourage researchers to explore the possible link between obesity and time preference, as important insights are likely to result.

Human body size and body proportions are interpreted as markers of ethnicity, 'race,' adaptation to temperature, nutritional history and socioeconomic status. Some studies emphasize only one of these indicators and other studies consider combinations of indicators. To better understand the biocultural nature of human size and proportions a new study of the growth of Maya-American youngsters was undertaken in 1999 and 2000. One purpose of this research is to assess changes in body proportion between Maya growing up in the US and Maya growing up in Guatemala. Height and sitting height of 6-12-year-old boys and girls (n=360) were measured and the sitting height ratio [sitting height/height]x100, a measure of proportion, was calculated. These data are compared with a sample of Maya of the same ages living in Guatemala and measured in 1998 (n=1297). Maya-American children are currently 10.24 cm taller, on average, and have a significantly lower sitting height ratio, (i.e. relatively longer legs, averaging 7.02 cm longer) than the Guatemala Maya. Maya-American children have body proportions more like those of white children in the US than like Maya children in Guatemala. Improvements in the environment for growth, in terms of nutrition and health, seem to explain both the trends in greater stature and relatively longer legs for the Maya-Americans. These findings are applied to the problem of modern human origins as assessed from fossil skeletons. It has been proposed that heat adapted, relatively long-legged Homo sapiens from Africa replaced the cold adapted, relatively short-legged Homo neandertalensis of the Levant and Europe [J Hum Evol 32 (1997a) 423]. Skeletal samples of Maya adults from rural Guatemala have body proportions similar to adult Neandertals and to skeletal samples from Europe with evidence of nutritional and disease stress. Just as nutrition and health status explains the differences in the body proportions of living Maya children, these factors, along with adaptation to climate, may also explain much of the differences between the Neandertal and African hominid samples.

Immigration from developing countries to the US generally increases access to health care and clean water, but it also introduces some unhealthy lifestyle patterns, such as diets dense in energy and little regular physical activity. We present a transdisciplinary model of child health and examine the impact of immigration on the physical growth and health of Maya children in Guatemala and the US. Maya-American children are much taller and have longer legs, on average, than their counterparts in Guatemala. This suggests that immigration to the US improves their health. However, the Maya-American children also are much heavier than both Guatemalan Maya and White American children, and have high rates of overweight and obesity. Quantile regression analysis indicates that Maya are shorter except in the upper tail of the stature distribution, and have higher Body Mass Index (BMI) in the tails, but not in the middle of the BMI distribution. Leisure time spent in front of a television or computer monitor tends to raise BMI in the middle and lower tail of the distribution, but not in the upper tail.

Migration of Maya refugees to the United States since the late 1970s affords the opportunity to study the consequences of life in a new environment on the growth of Maya children. The children of this study live in Indiantown, Florida, and Los Angeles, California. Maya children between 4 and 14 years old (n = 240) were measured for height, weight, fatness, and muscularity. Overall, compared with reference data for the United States, the Maya children are, on average, healthy and well nourished. They are taller and heavier and carry more fat and muscle mass than Maya children living in a village in Guatemala. However, they are shorter, on average, than children of black, Mexican-American, and white ethnicity living in Indiantown. Children of Maya immigrants born in the United States tend to be taller than immigrant children born in Guatemala or Mexico. Families that invest economic and social resources in their children have taller children. More economic successful families have taller children. Migration theory and political economy theory from the social sciences are combined with plasticity theory and life history theory (parental investment) from biology to interpret these data.

Social mammals have three basic stages of postnatal development: infant, juvenile, and adult. Some species also have a brief female post-reproductive stage. The human life cycle, however, is best described by five stages: infant, child, juvenile, adolescent, and adult. Women in both traditional and industrial societies may also have a long post-reproductive stage. Analyses of bones and teeth of early hominids who died as subadults suggest that the evolution of the new life stages of childhood and adolescence are not of ancient origin. The current human pattern evolved after the appearance of Homo erectus. It is possible that evidence for the existence of the post-reproductive stage for women will also be recoverable from the fossil record because the hormonal changes associated with menopause have profound effects on bone density and histology of tubular bones. It is hypothesized that the new life stages of the human life cycle represent feeding and reproductive specializations of the genus Homo. © 1996 Wiley-Liss, Inc., (Copyright © 1996 Wiley-Liss, Inc.)

The rate of growth in height and the timing of adolescent growth events are analyzed for two samples of Guatemalan children. One sample includes Mayan school children, 33 boys and 12 girls between the ages of 5.00 to 17.99 years, living under poor conditions for growth and development. The second sample includes ladino children, 78 boys and 85 girls of the same age range, living under favorable conditions for growth. The Preece-Baines model I function is used to estimate mean values for rates and timing of childhood and adolescent growth events for the two groups. Significant statistical contrasts (t-tests) of these means show Mayan boys reach the age of "take-off" (TO; the onset of the adolescent growth spurt) 1.45 years later, achieve peak height velocity (PHV) 1.68 years later, and continue growing for about 2.0 years longer than do the ladino boys. Despite the Mayan boys' increased duration for growth they grow significantly more slowly than the ladinos. Mayan boys are 6.60 cm shorter than ladinos at the age of TO and are estimated to be 7.71 cm shorter than the ladinos at adulthood. Mayan girls reach the age of TO 0.93 years later than do the ladina girls, but the two groups do not differ in the age at PHV or the age at adulthood. The mean height of Mayan girls is significantly less than that of ladinas at the age of TO (6.5 cm), and this difference increases to an estimated 11.14 cm at adulthood. Possible causes of these ethnic and sex-related differences in amounts and rates of growth are discussed in relation to hypotheses about the genetic and environmental determinants of human development.

The Preece-Baines model I function, adapted for use with a personal computer, is applied to the longitudinal growth records of Guatemalan children and adolescents of high socioeconomic status. The fit of the Preece-Baines function to the Guatemalan data is compared with those of published analyses of the function fitted to the growth of British, Belgian, urban and rural Indian, Australian Aborigine, and African children. Guatemalan, British, and Belgian samples share generally favorable environments for human development and show few differences in the amount and velocity of growth, or in the timing of growth events. Urban Indians live under relatively good environmental conditions and are similar to Guatemalans in the timing of growth events, but grow more slowly and grow less than the Guatemalans, British, or Belgians. Rural Indian, Australian, and African samples live in environments that delay or retard growth, and these last-named three samples grow more slowly, delay the onset of the adolescent growth spurt, and achieve smaller adult height than the Guatemalans. Parameters of the Preece-Baines model are compared between all samples and show that there are several alternate paths in the rate of growth and the timing of adolescent growth events that may be taken from childhood to adulthood., (Copyright © 1990 Wiley-Liss, Inc., A Wiley Company.)

Three longitudinal samples of Guatemalan schoolchildren are compared for amounts and rates of growth in height, weight, and bone age. The samples include children of two ethnic backgrounds: Ladinos, Spanish-speaking people of, generally, Western cultural orientation; and Indians, people of Mayan cultural descent. The Indians are of very low socioeconomic status (SES) and attend a public school in a rural village. The Ladinos come from two SES groups living in Guatemala City, one of high SES attending a private school and the other of low SES attending a public school. Graphical and statistical analyses show that for all samples of boys and girls there are generally, significant differences between samples (high SES>low SES>Indian) for amounts of growth in height, weight, and bone age. Boys show significant differences in rates of growth between samples, with the high SES sample growing more rapidly than the two low SES samples. Girls show significant differences in the rate of growth in height, but not in the rate of growth in weight or bone age. For Both boys and girls, rates of growth in height and weight differ more between samples than does rate of Skeltal development. These results demonstrate that (1) SES-related deficits in growth are cumulative during childhood and early adolescence, that (2) rates of growth for boys are, generally, more sensitive to the influence of SES than are the growth rates of girls, and that (3) childhood growth deficits of low SES children of low SES children are likely to carry over into adulthood., (Copyright © 1989 Wiley-Liss, Inc., A Wiley Company.)

Longitudinal data from a study of child development in Guatemala City were used to describe the influence of socioeconomic status and sex on physical and cognitive growth status. The correlation between the growth status variables was also analyzed. The sample included 144 Guatemalan children, 46 of low SES, 52 of middle SES, and 46 of high SES. The children were students in 5 urban primary schools. 3 physical variables, height, weight, and skeletal age, were measured annually from first to sixth grade. Two cognitive variables, general intelligence and reading ability, were measured in grades 1, 3, 4, or 5. Significant differences between SES groups existed for all variables. However, the differences in each grade were greater for the cognitive measures than for the physical measures. Compared with high SES children, middle SES boys and low SES boys and girls experienced significantly greater delayed growth in height than in weight or skeletal age. It is possible that these height delays may result in a permanent reduction in stature. The only consistently significant sex-related difference was for skeletal age; girls were more mature than boys in each grade. When SES was statistically controlled, there was no significant correlation between physical and cognitive growth status for girls and only a few moderate but statistically significant correlations for boys.

The distribution of subcutaneous fat at the triceps and subscapular skinfold sites is described for four groups of children living in Guatemala. These groups are high socioeconomic status (SES) children of Ladino (mixed Spanish and Indian) ancestry, high SES children of European ancestry, low SES Ladino children, and very low SES Indian children. The method of Healy and Tanner (1981) is used, employing regression and principal components analysis of log transformed skinfold values to divide "fatness" into two uncorrelated variables: size (amount of fat) and shape (fat pattern). Significant differences exist between groups in size, with lower SES groups having less fat than higher SES groups. No significant difference in fat pattern exists between the high SES Ladino and high SES European children. Significant differences do exist between the high SES groups and the low SES groups. The relative amount of subscapular fat increases from the high SES Ladinos and high SES Europeans, to the low SES Ladinos, to the very low SES Indians. In the high SES European and high SES Ladino samples, girls have significantly more arm fat than boys. There is no significant difference in fat patterning between boys and girls in the two low SES samples. Finally, the relative amount of subscapular fat tends to increase with age in all four samples. These results indicate that fatness and fat patterning are independent anatomical characteristics, SES influences fat patterning; low SES children of both Ladino and Indian ancestry show greater reductions in arm fat than in trunk fat compared to high SES children, sexual dimorphism in fat patterning is SES dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Monthly increments of height for a sample of 164 Guatemala City school children are analyzed for the presence of a seasonal pattern in rates of growth. It is found that pre and post adolescent children follow a seasonal pattern of growth but adolescent children do not. It is suggested that the results are due to an effect of seasonal changes in ultraviolet light availability and the synthesis of vitamin D3 as mediated by the level of maturation of each child.

Monthly increments of weight growth for a sample of 246 Guatemala City private school children are analyzed for the presence of a seasonal pattern in rates of growth. Neither a seasonal pattern nor any other periodic rhythm is found. It is observed that a significantly greater number of children aged 5.0 to 6.9 years experience their minimum annual growth rate during the dry season, with up to 60% of them losing or not gaining weight in any one month. Patterns of diet, exercise and disease cannot explain this trend. A possible association between minimum weight growth and maximum growth in height is discussed.

Schooling is considered by many researchers and agencies as an important contributor to individual and national development for populations living in the less developed countries. Accordingly, programs to increase school enrollment and continuation from grade to grade are being developed for many of these countries. This paper investigates the relationship of physical growth status (height, weight, and body composition), grade in school, and age to school continuation for a sample of Indian children living in a village near Guatemala City. It was found that physical growth status, a reflection of health and nutritional status, does not predict school continuation. A child's age and current grade in school do predict continuation. Most children leave school after reaching 9 years of age or after completing the second grade. It is suggested that children may learn enough to satisfy their parents' expectations by this age or grade. Also, the child's economic value to his or her family may be a significant reason for school drop-out.

Three groups of children, those of European parentage, those of Guatemalan parentage, and those of mixed European-Guatemalan parentage were measured for height, weight, and skeletal maturity. The children were born between 1945 and 1965, they were all of high socioeconomic status, and they all attended the same private school in Guatemala City. At 7 years, the boys of the European group were significantly taller than boys of the Guatemalan group. European and mixed European-Guatemalan girls were significantly taller than Guatemalan girls. These results are maturity independent. The influence of skeletal age was removed statistically by analysis of covariance. Girls of the mixed group were significantly heavier than girls of European and Guatemalan groups. Mixed group girls also had more significantly advanced skeletal ages than European girls. When the patterns of size and maturity status are analyzed by sex, there is evidence for a relatively greater environmental influence on the boys and a relatively greater genetic influence on the girls. Dividing the data into two birth year cohorts, 1945 to 1955, and 1956 to 1965, does not provide evidence for secular trends in growth or maturation. These results are similar to those from studies in developed nations that report an end to the secular trend for the "well off" population of those countries.