Seasonal variation in basal metabolic rates among the Yakut (Sakha) of Northeastern Siberia

OBJECTIVES

Previous research has shown that indigenous circumpolar populations have elevated basal metabolic rates (BMRs), yet few studies have explored whether metabolic rates increase during the winter. This study addresses this gap by examining seasonal variation in BMR and its associations with thyroid function and lifestyle factors among the Yakut (Sakha) of Siberia.

METHODS

Anthropometric dimensions, BMR, and thyroid hormone levels (free triiodothyronine [fT3], free thyroxine [fT4], thyroid-stimulating hormone [TSH]) were measured on two occasions (July/August, 2009 and January 2011) on a sample of 94 Yakut (Sakha) adults (35 men, 59 women) from the rural village of Berdygestiakh, Sakha Republic, Russia.

RESULTS

Seasonal changes in BMR varied by age. Younger Yakut adults (19-49 years) showed significant elevations in winter-time BMR of 6% (P < 0.05), whereas older individuals (≥50 years) showed modest declines (2%; n.s.). Both younger and older Yakut men and women showed increased respiratory quotients during the winter. FT3 and fT4 levels significantly declined during the winter in both younger and older Yakut men and women (P < 0.05). Lifestyle factors were significant predictors of BMR variation, particularly among older men and women.

CONCLUSIONS

Among the Yakut, increased wintertime BMR was observed among younger but not older adults, whereas all adults showed sharp reductions in free thyroid hormone levels during the winter. Among men, greater participation in subsistence activities was associated with increased BMRs and greater fat oxidation. Among women, variation in food use had the strongest impact on metabolic function.

Health and adult productivity: the relation between adult nutrition, helminths, and agricultural, hunting, and fishing yields in the Bolivian Amazon

OBJECTIVES

Infectious disease and nutritional stress have both been associated with reductions in adult work productivity and work capacity in the context of wage labor, but less research has investigated their effects among groups relying on more traditional subsistence practices of horticulture and foraging. In this article, we examine the relations among measures of adult nutritional status (BMI, skinfold measurements, and fat-free mass) and infection (presence of soil transmitted helminth infections) and measures of adult work productivity.

METHODS

As part of a larger panel study among Tsimane', a foraging-horticulturalist group in the Bolivian Amazon, health surveys, anthropometric information, and the quantity of products (both crops and game) brought into the household were collected for 320 Tsimane' adults over a four-month period in 2003. In addition, a single fecal sample was collected for a sub-sample of 86 adults.

RESULTS

Our analysis shows mixed associations between either BMI or the presence of parasitism and reported adult productivity. Muscularity was not clearly related to adult productivity. In contrast, body fatness (Skinfold z-score) was inversely associated with the average quantity of fish and game brought into the household, especially for men.

CONCLUSIONS

These findings suggest that the effects of adult infection and nutritional stress may be less clearly identified outside of the context of wage labor. Further research linking adult physical activity levels and metabolic rates to productivity in diverse contexts is needed.

Maintenance versus growth: investigating the costs of immune activation among children in lowland Bolivia

Immune function is a central component of maintenance effort, and it provides critical protection against the potentially life threatening effects of pathogens. However, immune defenses are energetically expensive, and the resources they consume are not available to support other activities related to growth and/or reproduction. In our study we use a life history theory framework to investigate tradeoffs between maintenance effort and growth among children in a remote area of Amazonian Bolivia. Baseline concentrations of C-reactive protein (CRP) were measured in 309 2- to 10-year olds as an indicator of immune activation, and height was measured at baseline and three months later. Elevated CRP at baseline predicts smaller gains in height over the subsequent three months, with the costs to growth particularly high for 2- to 4-year olds and for those with low energy reserves (in the form of body fat) at the time of immunostimulation. These results provide evidence for a significant tradeoff between investment in immunity and growth in humans, and highlight an important physiological mechanism through which maintenance effort may have lasting effects on child growth and development.

Rain, temperature, and child-adolescent height among Native Amazonians in Bolivia

BACKGROUND

Global climate change and recent studies on early-life origins of well-being suggest that climate events early in life might affect health later in life.

AIM

The study tested hypotheses about the association between the level and variability of rain and temperature early in life on the height of children and adolescents in a foraging-farming society of native Amazonians in Bolivia (Tsimane').

SUBJECT AND METHODS

Measurements were taken for 525 children aged 2-12 and 218 adolescents aged 13-23 in 13 villages in 2005. Log of standing height was regressed on mean annual level and mean intra-annual monthly coefficient of variation (CV) of rain and mean annual level of temperature during gestation, birth year, and ages 2-4. Controls include age, quinquennium and season of birth, parent's attributes, and dummy variables for surveyors and villages.

RESULTS

Climate variables were only related with the height of boys age 2-12. The level and CV of rain during birth year and the CV of rain and level of temperature during ages 2-4 were associated with taller stature. There were no secular changes in temperature (1973-2005) or rain (1943-2005).

CONCLUSION

The height of young females and males is well protected from climate events, but protection works less well for boys ages 2-12.

Ethnobotanical knowledge is associated with indices of child health in the Bolivian Amazon

Culture is a critical determinant of human behavior and health, and the intergenerational transmission of knowledge regarding the use of available plant resources has historically been an essential function of culture. Local ethnobotanical knowledge is important for health and nutrition, particularly in rural low-resource settings, but cultural and economic transitions associated with globalization threaten such knowledge. This prospective study investigates the association between parental ethnobotanical knowledge and child health among the Tsimane', a horticulturalist and foraging society in Amazonian Bolivia. Anthropometric data and capillary blood samples were collected from 330 Tsimane' 2- to 10-year-olds, and mothers and fathers were interviewed to assess ethnobotanical knowledge and skills. Comprehensive measures of parental schooling, acculturation, and economic activities were also collected. Dependent variables included three measures of child health: (i) C-reactive protein, assayed in whole-blood spots as an indicator of immunostimulation; (ii) skinfold thickness, to estimate subcutaneous fat stores necessary to fuel growth and immune function; and (iii) height-for-age, to assess growth stunting. Each child health measure was associated with maternal ethnobotanical knowledge, independent of a wide range of potentially confounding variables. Each standard deviation of maternal ethnobotanical knowledge increased the likelihood of good child health by a factor of >1.5. Like many populations around the world, the Tsimane' are increasingly facing the challenges and opportunities of globalization. These results underscore the importance of local cultural factors to child health and document a potential cost if ethnobotanical knowledge is lost.

Anthropometric variability in the USA: 1971-2002

AIM

The study analysed variability in physical stature, weight, and body mass index (BMI) in the USA during 1971-2002.

SUBJECTS

Subjects were non-Hispanic Blacks and Whites, 2-74 years of age from the National Health and Nutrition Examination Surveys (NHANES I-III and 1999-2002).

METHODS

The coefficient of variation and the standard deviation of the logarithm of stature, weight, and BMI were used to assess anthropometric variability for groups defined by age, race, sex, income, and survey year. Weighted ordinary least squares regressions were used to estimate the effect of socio-economic variables on anthropometric variability.

RESULTS

(a) The relation between age and variability in weight or BMI resembles an inverted U, (b) men have lower variability in BMI than women, (c) Blacks and the poor have greater variability in weight and BMI than Whites or than the non-poor, and (d) variability in anthropometric indices increased during 1971-2002. Results were robust to the measure of variability used and to the use of the mean and mean square of the anthropometric indicators as explanatory variables.

CONCLUSION

Since anthropometric indices correlate reliably with canonical indicators of well-being (e.g. income), growing variability in anthropometric indices, particularly among the Blacks and the poor, signals growing inequality in quality of life--a worrisome trend.

High-sensitivity C-reactive protein, adiposity, and blood pressure in the Yakut of Siberia

C-reactive protein (CRP), an acute-phase reactant and marker of inflammatory response, is known to be an important predictor of future cardiovascular mortality, independent of other risk factors. The purpose of this research was to investigate the association between CRP, adiposity, and blood pressure in the Yakut, an indigenous Siberian population undergoing rapid cultural change. We conducted a cross-sectional study of 265 healthy Yakut adults in six villages in rural northeastern Siberia. Plasma CRP was measured by high-sensitivity immunoturbidimetric assay. The median CRP value was 0.85 mg/l, with values for the 25th, 50th, and 75th percentiles of 0.30, 0.85, and 2.28 mg/l, respectively. CRP was positively associated with age (r = 0.19; P = 0.002), but not plasma lipids or smoking status. CRP was associated with measures of central adiposity and characteristics of the metabolic syndrome, particularly in women. We found significantly higher CRP across quintiles (Q) of waist circumference for women (difference = 0.7 mg/l; P = 0.035), but not men (difference = 0.36 mg/l; P = 0.515). CRP was significantly associated with systolic blood pressure in men (difference, Q1 vs. Q5 = 1.1 mg/l; P = 0.044) but not women (difference, Q1 vs. Q5 = 0.03 mg/l; P = 0.713) after adjusting for age, waist circumference, and smoking status. CRP in the Yakut was considerably lower than was reported for other populations. The low CRP levels may be explained in part by a low prevalence of abdominal obesity. Among the Yakut, the high physical-activity demands of a traditional herding lifeway likely play a role through high energy expenditure and maintenance of negative energy balance. Our findings underscore the need for further research on the metabolic activity of adipose tissue, blood pressure, and inflammatory activation in non-Western populations.

Health consequences of postsocialist transition: Dietary and lifestyle determinants of plasma lipids in Yakutia

The rapid social and cultural changes introduced by the collapse of the Soviet Union have resulted in important differences in cardiovascular health for indigenous Siberians. This study investigated diet and lifestyle determinants of plasma lipids in the Yakut, an indigenous Siberian herding population. The study used a cross-sectional design with data on 201 subjects in three urbanized towns and three rural communities in northeastern Siberia. Data on sociodemographic characteristics, dietary intake, and material lifestyle were collected, and lipids were analyzed from venous whole blood. Diet was analyzed using patterns of dietary intake based on principal components analysis of a dietary intake (food frequency) questionnaire. We identified three diet patterns: a traditional subsistence diet, a market foods diet, and a mixed diet. The effect of lifestyle on cardiovascular risk factors was measured using an ethnographically defined lifestyle index, with two orthogonal dimensions: subsistence lifestyle and modern lifestyle. Total cholesterol (TC) and low-density lipoprotein (LDL) were significantly higher among those consuming a traditional subsistence diet of meat and dairy products. A modern lifestyle was associated with lower TC and LDL but higher adiposity and higher risk of obesity. LDL and TC were higher in rural communities and lower in urbanized towns. The significantly higher lipid levels associated with a subsistence diet and indirectly with a subsistence lifestyle indicate the emergence of a significant health problem associated with the social and cultural changes occurring in Yakutia today. These findings underscore the need for dietary modification and promotion of physical activity among those most at risk for cardiovascular disease (CVD). Moreover, these results differ from those commonly seen in "modernizing" populations, in that elements of subsistence lifestyle are associated with an elevated rather than reduced risk of CVD. Such variable responses to lifestyle change emphasize the need to better understand the distinct social and historical events that may influence health changes among populations in transition.

Predictors of C-reactive protein in Tsimane' 2 to 15 year-olds in lowland Bolivia

Infectious disease is a major global determinant of child morbidity and mortality, and energetic investment in immune defenses (even in the absence of overt disease) is an important life-history variable, with implications for human growth and development. This study uses a biomarker of immune activation (C-reactive protein) to investigate an important aspect of child health among the Tsimane', a relatively isolated Amerindian population in lowland Bolivia. Our objectives are twofold: 1) to describe the distribution of CRP by age and gender in a cross-sectional sample of 536 2-15-year-olds; and 2) to explore multiple measures of pathogen exposure, economic resources, and acculturation as predictors of increased CRP. The median blood-spot CRP concentration was 0.73 mg/l, with 12.9% of the sample having concentrations greater than 5 mg/L, indicating a relatively high degree of immune activation in this population. Age was the strongest predictor of CRP, with the highest concentrations found among younger individuals. Increased CRP was also associated with higher pathogen exposure, lower household economic resources, and increased maternal education and literacy. The measurement of CRP offers a direct, objective indicator of immune activation, and provides insights into a potentially important pathway through which environmental quality may shape child growth and health.

Physical growth and nutritional status of Tsimane' Amerindian children of lowland Bolivia

This study examines patterns of growth and nutritional status of indigenous Tsimane' children under 9 years of age (n = 199 boys and 210 girls), based on a cross-sectional sample from 58 villages from the Beni Deparment of lowland Bolivia. Compared with US children, Tsimane' children are quite short, with linear growth tracking at or below the US 5th centile in both sexes. The prevalence of low height-for-age ("stunting;" HA Z-scores </=-2) is 52% in boys and 43% in girls. In contrast, weight-for-height in Tsimane' children approximates the US median, with the prevalence of low weight-for-height ("wasting"; WH Z-scores </=-2) being only 4% and 6% in boys and girls, respectively. Tsimane' boys and girls are leaner than their US peers, but their levels of body fatness are not so low as to indicate severe energy stress. Arm muscularity of Tsimane' children is similar to that of their US age peers, and this suggests that they are not experiencing acute protein malnutrition. Variation in measures of nutritional status of Tsimane' children is modestly correlated with village-level differences. Degree of isolation, as measured by distance to urban centers or to primary forest, was not a strong predictor of children's anthropometric status. Rather, in both boys and girls, nutritional status was most strongly associated with number of teachers in the village, a measure of access to education. Comparative analyses indicate that high levels of statural growth stunting are common among indigenous populations throughout lowland South America. This problem appears to be largely attributable to poor dietary quality (diets low in key micronutrients) and high disease loads. Further research is needed to identify the specific causes and potential interventions for the high rates of childhood growth stunting in this region.

An ecomorphological model of the initial hominid dispersal from Africa

We use new data on the timing and extent of the early Pleistocene dispersal of Homo erectus to estimate diffusion coefficients of early Homo from Africa. These diffusion coefficients indicate more rapid and efficient dispersals than those calculated for fossil Macaca sp., Theropithecus darti, and Mesopithecus pentelicus. Increases in home range size associated with changes in ecology, hominid body size, and possibly foraging strategy may underlay these differences in dispersal efficiency. Ecological data for extant primates and human foragers indicate a close relationship between body size, home range size, and diet quality. These data predict that evolutionary changes in body size and foraging behavior would have produced a 10-fold increase in the home range size of H. erectus compared with that of the australopithecines. These two independent datasets provide a means of quantifying aspects of the dispersal of early Homo and suggest that rapid rates of dispersal appear to have been promoted by changes in foraging strategy and body size in H. erectus facilitated by changes in ecosystem structure during the Plio-Pleistocene.

Neandertal energetics and foraging efficiency

Mechanical interpretations of Neandertal skeletal robusticity suggest extremely high activity levels compared to modern humans. Such activity patterns imply high energy requirements; yet it has been argued that Neandertals were also inefficient foragers. The present study addresses this apparent conflict by estimating energy needs in Neandertals and then evaluating those estimates in the context of energetic and foraging data compiled for contemporary human foragers and nonhuman primates. Energy demands for Neandertals were determined by first predicting basal metabolic rates (BMR) from body weight estimates using human standards developed by the World Health Organization [FAO/WHO/UNU (1985) Energy and Protein Requirements. Report of the Joint FAO/WHO/UNU Export Committee, Geneva: WHO]. Total daily energy expenditure (kcal/day) was then estimated assuming high levels of physical activity (i.e., 2--3 x BMR), comparable to those observed among subsistence-level populations today. These estimates of energy requirements (ranging from 3000--5500 kcal/day) were then used to determine Neandertal foraging efficiency assuming (1) minimal survival-level foraging returns, and (2) daily foraging times longer than those observed among any contemporary foraging group and comparable to a nonhuman primate. Even with these extremely conservative parameters, estimates of Neandertal foraging efficiency (approximately 800--1150 kcal/h foraged) were comparable to those observed among living hunter-gatherers. These results indicate that if Neandertals did have heavy activity levels, as implied by their skeletal robusticity, they would have required foraging efficiencies within the range observed among modern groups. Thus, Neandertals could have been either highly active or poor foragers, but they could not have been both.

Assessing the influence of physical activity on health and fitness

Increasing rates obesity and related chronic diseases in the United States and other parts of the world appear to be partly attributable to declining levels of physical activity. Given that adult obesity and chronic diseases often have their origins in childhood, there is a critical need to better understand how activity and fitness levels in childhood and adolescence shape health status in adulthood. The four papers in this series on physical activity draw on several longitudinal studies to examine the relationships between levels of physical activity and health-related fitness in childhood and adolescence to those in adulthood. These studies consistently demonstrate that adult activity levels and associated health outcomes are only modestly correlated with activity and fitness measures from childhood and adolescence. However, it appears that the methodological limitations in measuring activity levels may result in an underestimation of the importance of the influence of physical activity on health. Newer methods of measuring activity and energy expenditure offer to substantially improve our understanding of the influence of activity patterns on human health and fitness. Such information is necessary for promoting lifestyle changes that will reduce the risks of obesity and other chronic diseases.

Caretakers, child care practices, and growth failure in highland Ecuador

Problems for child health have been attributed to child and sibling caretaking. Nevertheless, our data from highland Ecuador suggest an ambiguous relationship between growth failure and the practice of peer care. In a region where levels of chronic undernutrition as measured by stunting exceed 75 percent and fully one-quarter of children under five are underweight, analysis of structured observations of a sample of 28 children reveals no statistical association between growth indices and the practice of older children caring for younger children. Qualitative data, however, indicate that the practice can be a complication in specific cases where children already suffer compromised health. While the advantages or disadvantages associated with particular caretakers appear secondary to the risks attending inadequate diets or the broader environment of rural poverty, the potential for difficulties to emerge from peer care suggests that community day care provides a valuable alternative in this context.

Distribution of the 3' VNTR polymorphism in the human dopamine transporter gene in world populations

A polymorphism with a variable number of tandem repeats (VNTR) found in the 3' untranslated region of the human dopamine transporter gene (DAT1) was scored in unrelated individuals drawn from 10 geographically widely dispersed populations in order to assess this marker's usefulness in human population genetics. The populations that were analyzed in this study included 4 indigenous groups of Siberia, natives of North and South America, as well as Caucasian and Oceanic groups, most of which represented small-scale societies. A total of 5 DAT1 alleles were seen overall, but only in one Siberian population, the Altai-Kizhi, were all 5 present, and in the Native Americans of Colombia the locus was monomorphic. The most common allele, DAT1*10, ranged in frequency from 52% in Greeks to 100% in South Americans. The high frequency of the DAT1*10 allele (approximately 90%) among Mongoloid groups of north and east Asia distinguishes them from most Caucasian groups. The presence of the rare DAT1*7 allele in relatively high frequency (approximately 5%) among all Siberian groups suggests a close affinity with north Asian groups, especially Mongolians. The presence of the even rarer DAT1*13 allele in one Siberian population, the Altai-Kizhi, reflects this group's long historical contact with Mongolians. The results demonstrated that the DAT1 VNTR polymorphism is useful in investigating population relationships, and that rare alleles at this locus may be particularly valuable in understanding the extent of genetic affinity between neighboring groups and in situations where admixture is suspected. However, because of both the association and linkage of this VNTR locus with attention-deficit hyperactivity disorder (ADHD) in children, and its highly restricted polymorphism (usually 3 alleles) in most human groups, the possibility of selection constraints on the DAT1 gene cannot be ignored.

Nutrition, thyroid function and basal metabolism of the Evenki of central Siberia

Considerable research has shown that indigenous circumpolar populations have elevated basal metabolic rates (BMR). Such elevations are likely promoted by changes in thyroid hormone levels; however, to date, this link between thyroid function and variation in BMR has not been explicitly demonstrated in an indigenous northern group. Thus, the purpose of this paper is to examine 1) the influence of dietary and nutritional factors on variation in thyroid hormone levels, and 2) the influence of thyroid levels on BMR in a sample of indigenous Siberian herders (the Evenki). Measures of body size and composition, dietary intake, thyroid hormones (total and free T3 and T4), thyroid stimulating hormone (TSH) and BMR were obtained for 60 adult subjects (19 males; 41 females) ranging in age from 18-56 years. Thyroid hormone levels in the Evenki were significantly correlated with measures of dietary intake and body composition. Among men, total T3 levels were positively correlated with body weight and fat-free mass (FFM), and negatively correlated with percent body fat; free T4 levels were positively correlated with dietary energy, protein and fat consumption. Among wo-men, there were no clear associations between body composition and thyroid levels; however, dietary energy and protein intakes were po-sitively correlated with total T4 and free T3 levels, respectively. Variation in thyroid hormone levels was associated with differences in BMR. In both sexes, deviations from predicted BMR were positively correlated with free T4 levels. These results demonstrate a link between thyroid hormones and elevated BMR in an indigenous circumpolar population. Further, they show the importance of dietary and nutritional factors for influencing thyroid function and, in turn, metabolic rates among such northern groups.

The central Siberian origin for native American Y chromosomes

Y chromosomal DNA polymorphisms were used to investigate Pleistocene male migrations to the American continent. In a worldwide sample of 306 men, we obtained 32 haplotypes constructed with the variation found in 30 distinct polymorphic sites. The major Y haplotype present in most Native Americans was traced back to recent ancestors common with Siberians, namely, the Kets and Altaians from the Yenissey River Basin and Altai Mountains, respectively. Going further back, the next common ancestor gave rise also to Caucasoid Y chromosomes, probably from the central Eurasian region. This study, therefore, suggests a predominantly central Siberian origin for Native American paternal lineages for those who could have migrated to the Americas during the Upper Pleistocene.

Climatic influences on human body size and proportions: ecological adaptations and secular trends

This study reevaluates the long-standing observation that human morphology varies with climate. Data on body mass, the body mass index [BMI; mass (kg)/stature (m)2], the surface area/body mass ratio, and relative sitting height (RSH; sitting height/stature) were obtained for 223 male samples and 195 female samples derived from studies published since D.F. Roberts' landmark paper "Body weight, race, and climate" in 1953 (Am. J. Phys. Anthropol. 11:533-558). Current analyses indicate that body mass varies inversely with mean annual temperature in males (r=-0.27, P < 0.001) and females (r=-0.28, P < 0.001), as does the BMI (males: r=-0.22, P=0.001; females: r=-0.30, P < 0.001). The surface area/body mass ratio is positively correlated with temperature in both sexes (males: r=0.29, P < 0.001; females: r=0.34, P < 0.001), whereas the relationship between RSH and temperature is negative (males: r=-0.37, P < 0.001; females: r=-0.46, P < 0.001). These results are consistent with previous work showing that humans follow the ecological rules of Bergmann and Allen. However, the slope of the best-fit regressions between measures of body mass (i.e., mass, BMI, and surface area/mass) and temperature are more modest than those presented by Roberts. These differences appear to be attributable to secular trends in mass, particularly among tropical populations. Body mass and the BMI have increased over the last 40 years, whereas the surface area/body mass ratio has decreased. These findings indicate that, although climatic factors continue to be significant correlates of world-wide variation in human body size and morphology, differential changes in nutrition among tropical, developing world populations have moderated their influence.

Demographic and socioeconomic determinants of variation in food and nutrient intake in an Andean community

Understanding the sources of variation in a community's diet is vital for development work, as well as being a source of anthropological and cultural insights. Previous surveys in the South American Andes suggest that nutrient deficiencies may be widespread; however, such interpretations have remained tentative since variance in Andean populations' diet has not been thoroughly examined. In this paper we consider the variation in diet due to variation in age, sex, and socioeconomic status and variation attributed to inter- and intraindividual variation in the diet. One to six days of dietary data (mean = 3.1) were collected via 24 h recalls from 221 residents of a small, rural community in highland Ecuador. The contribution of various food groups to the diet varied with land holdings and age but not sex. For example, animal-derived foods contribute more and tubers contribute less to the diet of the households with > or = 5 Ha, and sweets contribute more to the diet of children. The interindividual variation in energy and nutrient intake was low and the intraindividual variation high relative to developed countries. The consequence are twofold. First, because interindividual variability is low, group mean intake can be estimated relatively easily, facilitating group comparisons. Second, because intraindividual variation is high, individual nutrient intake cannot be easily estimated, which will decrease the ability to detect associations between nutrient intake and health measures. This knowledge of the sources of dietary variation can lead to better study and survey designs in the rural Andes and elsewhere in the developing world.

Underestimation of daily energy expenditure with the factorial method: implications for anthropological research

Under field conditions, total daily energy expenditure (TDEE) has generally been estimated using time allocation techniques (the factorial method). However, recent work suggests that the factorial method underestimates TDEE relative to newer, more accurate methods such as doubly labelled water (DLW) and heart-rate (HR) monitoring. This study compares estimates of TDEE obtained by the factorial and HR-monitoring methods for a sample of 61 indigenous (Evenki; 17 males, 44 females) and 32 nonindigenous ("Russian"; 10 males, 22 females) subjects from three communities in Central Siberia. Energy expenditures obtained from the two methods were significantly correlated (r = 0.495; P < 0.0001), but the factorial method significantly underestimated TDEE relative to the HR-monitoring technique (8.95 +/- 2.73 vs. 8.25 +/- 1.34 MJ/d; P < 0.005). Interpopulational analyses of data compiled from this and other studies indicate that the factorial method consistently underestimates TDEE relative to DLW and HR monitoring and that the magnitude of underestimation increases with expenditure levels. Indeed, among sedentary populations, factorial estimates of TDEE converge on those of the other methods, whereas at high activity levels the disparity is quite large. These results imply that the daily energy requirements of many subsistence-level populations have been underestimated, thus providing an overly favorable picture of energy balance. Moreover, it is likely that underrepresentation of TDEE is most problematic in rural societies of the developing world which tend to have high activity levels and great risk of malnutrition.

The China Productivity Project: results and conclusions

Experiments were conducted to determine what factors cause variation in individual work output (economic productivity). Forty-five young male Chinese cycle haulers from Beijing were assessed for physiological work capacity, size and body composition, health, nutritional status, cold resistance, household social environment, and motivation. Experiments were conducted in the laboratory as well as under actual working conditions; ethnographic observations were made in the household and on the job during the Beijing winter of 1992. Overall work motivation correlated to actual monthly distance/load measures of productivity the most strongly (r = 0.518), followed by physiological capacity estimated by heart rate:speed ratio during field experiments (r = -0.473). Alcohol consumption (a negative factor), household health, and carbohydrate intake were all moderate predictors. Maximum oxygen uptake showed lower correlation (r = 0.261), and among anthropometric values only relatively long lower legs were predictive (r = 0.298). Since many of these variable categories were relatively independent of each other, multiple regression analysis showed that together they explained 61.6% of the work output variance. Simultaneous prediction by FASEM (LISREL) is also very strong.

Recent fertility and mortality trends among aboriginal and nonaboriginal populations of central Siberia

We examine mortality and fertility patterns of aboriginal (primarily Evenki and Keto) and Russian (i.e., nonaboriginal) populations from the Baykit District of Central Siberia for the period 1982-1994. Mortality rates in the aboriginal population of Baykit are substantially greater than those observed in the Russians and are comparable to levels recently reported for other indigenous Siberian groups. Infant mortality rates average 48 per 1000 live births among Baykit aboriginals, three times greater than the Russians of the district (15 per 1000 births) and more than double the rates for Inuit and Indian populations of Canada. Similarly, crude death rates of the Baykit aboriginals are twice as high as those observed in either the Baykit Russians or the Canadian aboriginal populations (13 vs 6-7 deaths per 1000 individuals). Birth rates of the indigenous population of Baykit are higher than those of the Russians (33 vs. 15 births per 1000 individuals) but are comparable to those of Canadian aboriginal groups. Violence and accidents are the leading causes of adult male mortality in both ethnic groups, whereas circulatory diseases have emerged as the prime cause of death in women. The greater male mortality resulting from violence and accidents is a widely observed cross-cultural phenomenon. The emergence of circulatory diseases as a major mortality risk for women, however, appears to be linked to specific lifestyle changes associated with Soviet reorganization of indigenous Siberian societies. Marked declines in mortality and increases in fertility were observed in the Baykit aboriginal population during the mid to late 1980s with the government's implementation of anti-alcohol policies. The decline in mortality, however, was largely erased during the early 1990s, as the region became increasingly isolated and marginalized following the collapse of the Soviet Union. Demographic trends in the Baykit District suggest that because the indigenous groups have become more isolated, many are returning to a more traditional subsistence lifestyle.

Comparative primate energetics and hominid evolution

There is currently great interest in developing ecological models for investigating human evolution. Yet little attention has been given to energetics, one of the cornerstones of modern ecosystem ecology. This paper examines the ecological correlates of variation in metabolic requirements among extant primate species, and uses this information to draw inferences about the changes in energy demands over the course of human evolution. Data on body size, resting metabolism, and activity budgets for selected anthropoid species and human hunter-gatherers are used to estimate total energy expenditure (TEE). Analyses indicate that relative energy expenditure levels and day ranges are positively correlated with diet quality; that is, more active species tend to consume more energy-rich diets. Human foragers fall at the positive extremes for modern primates in having high expenditure levels, large ranges, and very high quality diets. During hominid evolution, it appears that TEE increased substantially with the emergence of Homo erectus. This increase is partly attributable to larger body size as well as likely increases in day range and activity level. Assuming similar activity budgets for all early hominid species, estimated TEE for H. erectus is 40-45% greater than for the australopithecines. If, however, it is assumed that the evolution of early Homo was also associated with a shift to a more "human-like" foraging strategy, estimated expenditure levels for H. erectus are 80-85% greater than in the australopithecines. Changing patterns of resource distribution associated with the expansion of African savannas between 2.5 and 1.5 mya may been the impetus for a shift in foraging behavior among early members of the genus Homo. Such ecological changes likely would have made animal foods a more attractive resource. Moreover, greater use of animal foods and the resulting higher quality diet would have been important for supporting the larger day ranges and greater energy requirements that appear to have been associated with the evolution of a human-like hunting and gathering strategy.

Differences between observed and predicted energy costs at rest and during exercise in three subsistence-level populations

Estimates of daily energy expenditure are important for many areas of research in human ecology and adaptability. The most common technique for estimating human energy expenditure under field conditions, the factorial method, generally relies on activity-specific energy costs derived from published sources, based largely on North American and European subjects. There is concern that such data may not be appropriate for non-Western populations because of differences in metabolic costs. The present study addresses this concern by comparing measured vs. predicted energy costs at rest and during sub-maximal exercise in 83 subjects (52 males, 31 females) from three subsistence-level populations (Siberian herders and highland and coastal Ecuadorian farmers). Energy costs at rest (i.e., lying, sitting and standing) and while performing a standard stepping exercise did not significantly differ among the three groups. However, resting energy costs were significantly elevated over predicted levels (+ 16% in men, + 11% in women), whereas exercising costs were comparable to predicted values (-6% in men, + 3% in women). Elevations in resting energy needs appear to reflect responses to thermal stress. These results indicate that temperature adjustments of resting energy costs are critical for accurately predicting daily energy needs among traditionally living populations.

Population distributions of APOE, APOH, and APOA4 polymorphisms and their relationships with quantitative plasma lipid levels among the Evenki herders of Siberia

We examined the distributions of seven polymorphic sites in three apolipoprotein genes (APOE, APOA4, and APOH) and their relationships with quantitative lipid levels (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) among the Evenki reindeer herders of central Siberia. The polymorphism data reveal several distinctive features that differentiate the Evenki from white populations: the near absence of the APOE*2 allele, the highest ever recorded frequency of the APOH*3 allele, the complete absence of the APOA*2 allele at codon 360, and significantly different frequencies at three other APOA4 polymorphic sites. Our analyses of the relationships of common apolipoprotein polymorphism and plasma lipid levels also revealed interesting results. The well-established positive association between the APOE*4 allele and LDL cholesterol level reported in white populations was not seen in the Evenki despite a comparable frequency of the APOE*4 allele. Because the Evenki have significantly lower cholesterol levels than Westernized whites, this difference in allelic effect probably reflects gene-diet interaction, which modulates the effect of APOE polymorphism on LDL cholesterol. At the APOA4 locus the HincII polymorphism at codon 127 shows a significant impact on plasma triglyceride variation in the Evenki sample: The HincII - allele was associated with higher triglyceride levels than the HincII + allele. Our data indicate that both the genetic and the environmental factors conventionally associated with cardiovascular disease risk in Western societies are different in the Evenki.

Growth differences between children of highland and coastal Ecuador

This study examines patterns of growth in height and weight among children (< 60 months) of highland and coastal agricultural communities of Ecuador. Highland children are significantly shorter, but not significantly lighter than their coastal peers. Linear growth rates (cm/6 months) are comparable between the two samples. Growth rates for body weight (kg/6 m) are similar in highland and coastal boys, whereas highland girls display larger weight gains than their coastal counterparts. In both regions, linear growth is compromised to a much greater extent than growth in body weight, and growth faltering for both height and weight is most pronounced between birth and 24 months of age. The similarity in growth rates between the highland and coastal samples suggests that high altitude hypoxia plays a relatively small role in shaping growth during the first five years after birth. Rather, it appears that most of the disparity in height between the two samples can be attributed to differences established by 6 months of age. The pattern of growth retardation seen in both regions during the first 24 postnatal months is similar to that observed among impoverished populations throughout the world and is likely associated with the influence of nutritional and disease stressors. After 2 years of age, little or no "catch up" growth is seen in height, whereas improvements in weight gain are more pronounced, especially among highland girls. Ongoing research is investigating the nutritional and socio-economic correlates of growth within each region.

Population relationships among historical and modern indigenous Siberians based on anthropometric characters

A comparison of anthropometric data recently collected from a modern population of Evenki and data collected from a group of Evenki at the turn of the century by the Jesup expedition (Boas 1903) reveals a pattern of significant changes over this time period. The modern Evenki exhibit larger sitting height and biacromial breadth but smaller bizygomatic and nasal breadth and a shorter face. Although the differences in the postcranial characters might be attributable to improvements in health and nutrition over time, those of the head and face might also indicate increased gene flow, perhaps from European populations. The comparative analysis of the anthropometric data was expanded to a multivariate approach by use of canonical variate analysis. This analysis was performed using data from the 10 populations sampled during the Jesup expedition along with the data from a sample of modern Evenki. In general, a pattern of relationships emerged, reflecting known population interactions and linguistic affiliations to a certain extent. However, the sample of modern Evenki differed substantially from all the other samples in the analysis. Although such a separation of the modern Evenki from this set of historical Siberian populations may be the result of a secular trend; it is also highly probable that it reflects new patterns of gene flow resulting from interactions and events associated with Russian colonial expansion and in this century the establishment of the Soviet state.

Comparison of the heart rate-monitoring and factorial methods: assessment of energy expenditure in highland and coastal Ecuadoreans

Accurate estimates of total daily energy expenditure (TDEE) are critical to studies of the nutritional adaptation of human populations. This study compared the standard factorial method with the recently developed flex-HR technique in a sample of 32 adults (16 males, 16 females) from rural, agricultural communities of highland and coastal Ecuador. Although energy expenditures obtained from the two methods were highly correlated (r = 0.759, P < 0.0001), the 1985 FAO/WHO/UNU factorial method significantly underestimated TDEE relative to the heart rate-monitoring technique (10.27 +/- 2.54 compared with 11.91 +/- 3.96 MJ/d, P < 0.001). The degree of underestimation was greater in males, who had higher energy expenditures. Similarly, underestimation was greater in the highland farmers, who were studied during a period of heavy agricultural work. The differences in energy expenditure estimates translated into a 10% difference in estimated energy adequacy. Additional research is needed to identify the potential sources of bias in the factorial method and to further develop other techniques for accurately estimating energy expenditure under field conditions.

VNTR DNA variation in Siberian indigenous populations

The VNTR loci D7S104, D11S129, D18S17, D20S15, and D21S112 in three indigenous Siberian populations were analyzed to determine the populations' genetic structure. Using the Kolmogorov-Smirnov test, we found that the Siberian indigenous populations of Surinda and Sulamai are separated at the D11S129 locus (p < 0.05). However, the population of Poligus is genetically homogeneous compared with the villages of Sulamai and Surinda. Principal component plots for the sets of VNTR loci cluster the Siberian groups together, reflecting the homogeneity of these populations. An analysis of mean per locus heterozygosity versus the distance from the centroid of distribution suggests gene flow into Sulamai but little genetic exchange with Surinda and Poligus. Ultimately, the VNTR data reflect the genetic distinctiveness of the Kets and the Evenki.

Household-level strategies for protecting children from seasonal food scarcity

Although it has been widely argued that children are most severely affected during periods of food scarcity, there is little quantitative data to support this claim. The present study uses dietary intake and anthropometric data from the Andean community of Nuñoa, Peru to evaluate age-related differences in the impact of and responses to seasonal variation in food availability. Children ages 12 years and under experience smaller seasonal fluctuations in energy intake and have a more adequate pre-harvest diet than adults. Anthropometric measures (weight-for-age and skinfold thicknesses) also indicate better nutritional status in children. Protection of children against severe pre-harvest stress is important because (1) they are more vulnerable to nutritional deprivation and (2) they make substantial contributions to household production. Gender differences, however, are not apparent as nutritional adequacy is comparable in males and females. Protection of children against nutritional stress represents just one of a suite of adaptive responses to limited pre-harvest food availability exhibited within this population.

What did our ancestors eat?

Over the millennia various hominoids and hominids have subsisted on very different dietaries, depending on climate, hunting proficiency, food-processing technology, and available foods. The Australopithecines were not browsers and fruit-eaters with very high intakes of vitamin C; rather they were scavengers of kills made by other animals. The hominids who followed did include some cold-climate hunters of large game, but the amount of animal protein decreased with the advent of grain-gathering and decreased further with the introduction of cereal agriculture, with a concomitant decrease in body size. From what we know about food adequacy, preparation, and storage, the notion that the postulated "primitive" diet was generally adequate, safe, and prudent can be rejected. Over evolutionary time, many of our ancestors ate poorly, especially during climate extremes, and they were often at risk for vitamin deficiencies, food-borne diseases, and neurotoxins. Until the advent of modern processing technologies, dirt, grit, and fiber constituted a large part of most early diets.

Nutritional determinants of high-altitude growth in Nuñoa, Peru

Data on nutritional intake and patterns of physical growth in the rural Andean community of Nuñoa, Peru (elevation 4,000 m), are described and compared to data previously collected from this location. Food consumption data and selected anthropometric measures were obtained from a sample of 33 households. Estimates of caloric intake from this study are very similar to those obtained in Nuñoa during the mid- and late 1960s. However, within the present sample, upper income (i.e., middle class) individuals have significantly higher caloric intakes than those of the lower income group and also appear to have an improved diet relative to individuals of 20 years ago. Anthropometric data show that children of the upper socioeconomic status (SES) group are significantly taller and heavier than the lower SES group children. Moreover, the children of the wealthier families are taller and heavier than the children measured 20 years ago at the same location, whereas the poorer children are not. These results indicate that nutritional factors have significantly contributed to the extreme pattern of slow growth previously reported for children of Nuñoa and, moreover, demonstrate how social and environmental forces interact to create differential levels of stress that contribute to variation in biological well-being.

Protection of children from seasonal nutritional stress in an Andean agricultural community

Patterns of seasonal variation in energy intake among small scale farmers (n = 112 individuals) of the highland community of Nuñoa, Peru are examined. Marked seasonal fluctuations in energy consumption are demonstrated with average daily energy intakes being lowest during the last few months before harvest (January-April) when locally produced foods are in shortest supply. However, seasonal energy reduction does not affect all sectors of the population equally. Children (aged 12 years and under) show the least seasonal change in energy intake and appear to be protected from energy stress during the pre-harvest period. This pattern contradicts the generally held view that children are most severely affected under conditions of food scarcity because resources must be preferentially allocated to adult males. Hence, these results emphasize the need to examine further variation in responses to nutritional stress among human populations. It appears that such variation may be dependent upon (1) the nature of the subsistence economy, and (2) aspects of division of labour within populations.

Biosocial responses to seasonal food stress in highland Peru

This paper examines patterns of seasonal variation in food consumption and responses to food stress in the highland community of Nuñoa, Peru. Dietary and anthropometric data collected from January through August of 1985 on a sample of 26 households (127 individuals) are analyzed. This study finds sharp seasonal differences in energy intake (pre-harvest = 1150 calories/day; post-harvest = 1519/day; p less than 0.01) associated with variation in the availability of locally-produced products (e.g., tubers and cereals). Seasonal energy reduction, however, does not uniformly affect all sectors of this population. Children experience little seasonal change in energy intake and have a more adequate pre-harvest diet and better nutritional status than adults. The responses used to "protect" children from energy stress and minimize the overall impact of seasonal food scarcity on this community include: 1) reduction of pre-harvest household caloric needs through emigration of adolescent and adult males, 2) preferential allocation of food to children during the pre-harvest period, 3) seasonal reduction of activity levels and the year-round use of children for many productive activities, and 4) seasonal changes in meal patterns that minimize post-prandial energy loss during periods of stress. Evaluation of similar data from other anthropological populations underscores the diversity of responses to seasonal change in food availability. Moreover, these data indicate that the protection of children from seasonal energy stress is more common than previously thought. Variation in adaptive responses to food stress appears to be dependent upon 1) the nature of the subsistence economy, 2) the relative contributions of children and adults to household production, and 3) the demographic structure of the population.

Reflections on the face of Japan: a multivariate craniofacial and odontometric perspective

Craniofacial variables for modern and prehistoric Japanese were subjected to multivariate analysis to test the relationships of the people of Japan with mainland Asian and Oceanic samples. The modern Japanese are tied to Koreans, Chinese, Southeast Asians, and the Yayoi rice agriculturalists who entered Japan in 300 B.C. Together they make up a Mainland-Asia cluster of related populations. The prehistoric Jomon foragers, the original inhabitants of the Japanese archipelago, are the direct ancestors of the modern Ainu, who made a recognizable contribution to the warrior class--the Samurai--of feudal Japan. Together, they are associated with Polynesians and Micronesians in a Jomon-Pacific cluster of related populations. Jomon-to-Ainu tooth size reduction proceeded at the same rate as that observable in the post-Pleistocene elsewhere in the Old World.

Applications of the pattern variability index (sigma z) to the quantification of dysmorphogenesis in the hand

We have generated percentiles for the pattern variability index (sigma z) of the hand in 1,088 normal infants, children, and adults and have analyzed pattern variability indices for 820 individuals representing 50 congenital malformation syndromes with respect to the normal percentiles. The majority of the affected individuals exhibited elevated sigma z values for the hand, some vastly in excess of normal, while such syndromes as Down, Turner, and the Prader-Willi syndrome were low rather than high in pattern variability of the hand.

Evolution of P3 morphology in Australopithecus afarensis

The Australopithecus afarensis dental sample exhibits a wide range of variation, which is most notable in the morphology of the lower third premolar (P3). P3 morphology in the A. afarensis sample ranges from the primitive sectorial extreme in AL 128-23 to the derived, bicuspid (molarized) extreme in AL 333w-1. In this paper, the degree and patterning of variation of the 20 known A. afarensis P3s are examined and the evolutionary implications are discussed. Initially, a series of dental and mandibular metric criteria are evaluated to determine whether this sample may be analyzed as a single species. From the metrics, it is clear that the single species hypothesis cannot be rejected. Next, a series of morphological criteria is devised to measure P3 molarization. Taken as a whole, the A. afarensis P3 sample displays more variation than a sample of modern hominoids (Pan troglodytes) and shows a slight trend toward increased molarization through time. When separated by sex, the A. afarensis sample still displays greater variation than the chimpanzee sample; however, only the male A. afarensis specimens show a trend toward increased molarization. Additionally, the male A. afarensis P3s are more molarized than the female, a pattern that is seen as well (though less markedly) in the chimpanzee sample. The trend toward increased molarization over time indicates selection for grinding in A. afarensis. The sexual differences parallel those seen in the postcrania (cf. Stern and Susman: Am. J. Phys. Anthropol. 60:279-318, 1983), as the females tend to retain the primitive condition, while the males display the derived morphology. Consequently, a model of sexual differences in niche exploitation, with the females exploiting a more arboreal environment, would seem to be supported by both the dental and postcranial evidence.

Methods for measuring the strength of discriminable drug effects

Drug discriminations can be used to investigate a variety of preclinical psychopharmacological issues. These discriminations are based on the so-called "discriminable" or "discriminative stimulus" effects of drugs. In order to conduct some types of drug discrimination studies, it is helpful or necessary to know the amount or degree of discriminability of the various drugs employed. This paper describes several methods for determining the degree of discriminability of drugs, and evaluates these methods primarily using data obtained by training rats to discriminate drug vs. no drug in a shock-escape T-maze task. The results suggest that useful indices of degree of discriminability can be computed from the rapidity with which drug discriminations are learned. Indices based on average accuracy during acquisition were found to be somewhat superior to indices based on sessions to criterion.