Distribution by Scientific Domains

Selected Abstracts

The costs and benefits of fast living

ECOLOGY LETTERS, Issue 12 2009
Karen E. Rose
Abstract Growth rates play a fundamental role in many areas of biology (Q. Rev. Biol., 67, 1992, 283; Life History Invariants. Some Explorations of Symmetry in Evolutionary Biology, 1993; Philos. Trans. R. Soc. Lond. B Biol. Sci., 351, 1996, 1341; Plant Strategies, Vegetation Processes, and Ecosystem Properties, 2002; Trends Ecol. Evol., 18, 2003, 471; Q. Rev. Biol., 78, 2003, 23; J. Ecol., 95, 2007, 926.) but the cost and benefits of different growth rates are notoriously difficult to quantify (Q. Rev. Biol., 72, 1997, 149; Funct. Ecol., 17, 2003, 328). This is because (1) growth rate typically declines with size and yet the most widely used growth measure , relative growth rate or RGR (conventionally measured as the log of the ratio of successive sizes divided by the time interval) , is not size-corrected and so confounds growth and size, (2) organisms have access to different amounts of resource and (3) it is essential to allow for the long-term benefits of larger size. Here we experimentally demonstrate delayed costs and benefits of rapid growth in seven plant species using a novel method to calculate size-corrected RGR. In control treatments, fast-growing plants benefited from increased reproduction the following year; however, fast-growing plants subjected to an experimental stress treatment (defoliation) showed strongly reduced survival and reproduction the following year. Importantly, when growth was estimated using the classical RGR measure, no costs or benefits were found. These results support the idea that life-history trade-offs have a dominant role in life-history and ecological theory and that the widespread failure to detect them is partly due to methodological shortcomings. Ecology Letters (2009) 12: 1379,1384 [source]

Early neural activity and dendritic growth in turtle retinal ganglion cells

Vandana Mehta
Abstract Early neural activity, both prenatal spontaneous bursts and early visual experience, is believed to be important for dendritic proliferation and for the maturation of neural circuitry in the developing retina. In this study, we have investigated the possible role of early neural activity in shaping developing turtle retinal ganglion cell (RGC) dendritic arbors. RGCs were back-labelled from the optic nerve with horseradish peroxidase (HRP). Changes in dendritic growth patterns were examined across development and following chronic blockade or modification of spontaneous activity and/or visual experience. Dendrites reach peak proliferation at embryonic stage 25 (S25, one week before hatching), followed by pruning in large field RGCs around the time of hatching. When spontaneous activity is chronically blocked in vivo from early embryonic stages (S22) with curare, a cholinergic nicotinic antagonist, RGC dendritic growth is inhibited. On the other hand, enhancement of spontaneous activity by dark-rearing (Sernagor & Grzywacz (1996)Curr. Biol., 6, 1503,1508) promotes dendritic proliferation in large-field RGCs, an effect that is counteracted by exposure to curare from hatching. We also recorded spontaneous activity from individual RGCs labelled with lucifer yellow (LY). We found a tendency of RGCs with large dendritic fields to be spontaneously more active than small-field cells. From all these observations, we conclude that immature spontaneous activity promotes dendritic growth in developing RGCs. [source]

Nestling coloration is adjusted to parent visual performance in altricial birds irrespective of assumptions on vision system for Laniidae and owls, a reply to Renoult et al.

Abstract We have recently published support to the hypothesis that visual systems of parents could affect nestling detectability and, consequently, influences the evolution of nestling colour designs in altricial birds. We provided comparative evidence of an adjustment of nestling colour designs to the visual system of parents that we have found in a comparative study on 22 altricial bird species. In this issue, however, Renoult et al. (J. Evol. Biol., 2009) question some of the assumptions and statistical approaches in our study. Their argumentation relied on two major points: (1) an incorrect assignment of vision system to four out of 22 sampled species in our study; and (2) the use of an incorrect approach for phylogenetic correction of the predicted associations. Here, we discuss in detail re-assignation of vision systems in that study and propose alternative interpretation for current knowledge on spectrophotometric data of avian pigments. We reanalysed the data by using phylogenetic generalized least squares analyses that account for the alluded limitations of phylogenetically independent contrasts and, in accordance with the hypothesis, confirmed a significant influence of parental visual system on gape coloration. Our results proved to be robust to the assumptions on visual system evolution for Laniidae and nocturnal owls that Renoult et al. (J. Evol. Biol., 2009) study suggested may have flawed our early findings. Thus, the hypothesis that selection has resulted in increased detectability of nestling by adjusting gape coloration to parental visual systems is currently supported by our comparative data. [source]

Social semantics: how useful has group selection been?

Abstract In our social semantics review (J. Evol. Biol., 2007, 415,432), we discussed some of the misconceptions and sources of confusion associated with group selection. Wilson (2007, this issue) claims that we made three errors regarding group selection. Here, we aim to expand upon the relevant points from our review in order to refute this claim. The last 45 years of research provide clear evidence of the relative use of the kin and group selection approaches. Kin selection methodologies are more tractable, allowing the construction of models that can be applied more easily to specific biological examples, including those chosen by Wilson to illustrate the utility of the group selection approach. In contrast, the group selection approach is not only less useful, but also appears to frequently have negative consequences by fostering confusion that leads to wasted effort. More generally, kin selection theory allows the construction of a unified conceptual overview that can be applied across all taxa, whereas there is no formal theory of group selection. [source]


Article first published online: 24 SEP 200
Carmona, R.1, Kraemer G. P.2, Zertuche, J. A.3, Chanes, L.4, Chopin, T.5, Neefus C.4,6 & Yarish, C.1 1Dept. of Ecol. and Evol. Biol., University of Connecticut, One University Place, Stamford, CT 06901, USA; 2Department of Environmental Sciences, State University of New York, Purchase, NY 10577 USA; 3IIO, Universidad Autonoma de Baja California. Ensenada,B.C., Mexico; 4DGETI-CBTis41, Mexico; 5CCSA, Dept. of Biol., University of New Brunswick, Saint John, N.B., E2L 4L5, Canada; 6Department of Plant Biology, University of New Hampshire, Durham, NH 03824, USA Finfish mariculture along the Northeast US coast continues to develop into a strong industry. At a regional level, mariculture can be a significant contributor to nutrient loading in coastal waters. Since macroalgae are able to concentrate nutrients and grow at high rates, they can be an useful tool for alleviating this problem. In addition, seaweed mariculture is by itself a multi-billion dollar industry, with the red alga Porphyra (nori) valued at over $US 1.8 billion. Local species and strains of Porphyra from the Northeast U.S.A. are being studied to determine their capacity as nutrient scrubbers under different nutrient and temperature conditions. P. purpurea was grown under two N sources (NO3- vs. NH4+). The fastest growth (up to 13% d-1) and greatest N content (ca. 7% DW) were measured in plants grown at 300 µM NH4+. Short-term NH4+ uptake by P. purpurea (strains from Maine and Long Island Sound) and by P. amplissima was not saturated at 150 µM, the highest concentration tested. The P. purpurea isolate from Maine took up NH4+ faster than did the Long Island Sound isolate. NH4+ uptake by P. amplissima was faster than uptake by either P. purpurea strain. The high growth rates obtained and the ability for N uptake and tissue accumulation make these species suitable for using as a biological nutrient removal system. [source]

Sex differences in fetal growth responses to maternal height and weight

Michelle lampl
Sex differences in fetal growth have been reported, but how this happens remains to be described. It is unknown if fetal growth rates, a reflection of genetic and environmental factors, express sexually dimorphic sensitivity to the mother herself. This analysis investigated homogeneity of male and female growth responses to maternal height and weight. The study sample included 3,495 uncomplicated singleton pregnancies followed longitudinally. Analytic models regressed fetal and neonatal weight on tertiles of maternal height and weight, and modification by sex was investigated (n = 1,814 males, n = 1,681 females) with birth gestational age, maternal parity, and smoking as covariates. Sex modified the effects of maternal height and weight on fetal growth rates and birth weight. Among boys, tallest maternal height influenced fetal weight growth before 18 gestational weeks of age (P = 0.006), and prepregnancy maternal weight and body mass index subsequently had influence (P < 0.001); this was not found among girls. Additionally, interaction terms between sex, maternal height, and maternal weight identified that males were more sensitive to maternal weight among shorter mothers (P = 0.003) and more responsive to maternal height among lighter mothers (P , 0.03), compared to females. Likewise, neonatal birth weight dimorphism varied by maternal phenotype. A male advantage of 60 g occurred among neonates of the shortest and lightest mothers (P = 0.08), compared to 150 and 191 g among short and heavy mothers, and tall and light-weight mothers, respectively (P = 0.01). Sex differences in response to maternal size are under-appreciated sources of variation in fetal growth studies and may reflect differential growth strategies. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Pleiotropic effects on subclasses of HDL, adiposity, and glucose metabolism in adult Alaskan Eskimos

M. Elizabeth Tejero
The aim of this study was to analyze the heritability and the presence of pleiotropic effects on subfractions of high-density lipoproteins (HDLs) as measured by nuclear magnetic resonance (NMR), parameters for adiposity, and glucose metabolism in adult Alaskan Eskimos. The present family study included 1,214 adult Alaskan Eskimos (537 male/677 female). Body weight, height, circumferences, selected skinfolds, and blood pressure were measured in all participants. Blood samples were collected under fasting conditions for the isolation of plasma. Glucose, insulin, subclasses and size of lipoproteins, triglycerides, total, and HDL cholesterol and lipoprotein (a) were measured in plasma. HbA1c was measured in total blood. Univariate and bivariate quantitative genetic analyses were conducted between HDL subclasses and size and the anthropometric and biochemical measures using the variance decomposition approach. Variation in all the analyzed traits exhibits a significant genetic component. Heritabilities ranged between 0.18 ± 0.11 for LDL2 (intermediate) and 0.89 ± 0.07 for small HDL. No common genetic effects were found on the HDL subclasses (small, intermediate, and large). Small HDL particles were genetically correlated with LDL particles and HbA1c. Negative genetic correlations were observed between intermediate and large HDL subfractions, HDL size and measures of adiposity, and LDL and parameters for glucose metabolism (HbA1, insulin). These observations confirm the presence of possible pleiotropic effects on HDL, adiposity, and cardiovascular risk factors and provide novel insight on the relationship between HDL subclasses, adiposity, and glucose regulation. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Photoperiod at conception predicts C677T-MTHFR genotype: A novel gene-environment interaction

Mark Lucock
Data is presented, which suggest that the day length a woman experiences during the periconceptional period predicts the C677T-MTHFR genotype of her child. Logistic regression analysis involving 375 neonates born in the same geographical location within a three year period demonstrated that photoperiod (minutes) at conception predicts both genotype (P = 0.0139) and mutant allele carriage (P = 0.0161); the trend clearly showing that the 677T-MTHFR allele frequency increases as photoperiod increases. We propose a number of explanations, including a hypothesis in which a long photoperiod around conception decreases maternal systemic folate because of UVA induced dermal oxidative degradation of 5-methyl-H4folate, leading to a lower cellular 5,10-methylene-H4folate status. In this scenario, 5,10-methylene-H4folate would be more efficiently used for dTMP and DNA synthesis by 677T-MTHFR embryos than wildtype embryos giving the 677T-MTHFR embryos increased viability, and hence increasing mutant T-allele frequency. Alternate hypotheses include: increased seasonal availability of folate rich foods that genetically buffer any negative effect of 677T-MTHFR in embryos; seasonal oxidative stress lowering embryo-toxic homocysteine; an undefined hormonal effect of photoperiod on the neuroendocrine axis, which mediates genotype/embryo selection. The effect of photoperiod on genotype seems clear, but the speculative molecular mechanism underpinning the effect needs careful examination. Am. J. Hum. Biol., 2010. © 2010 Wiley-Liss, Inc. [source]

Offspring from endogamic vs. exogamic matings: Absence of anthropometric differences among Sardinian children (Italy)

E. Sanna
This study evaluates possible differences in body dimensions among children from matings of different exogamy levels. The cross-sectional sample consisted of 867 children, 435 males, and 432 females, 6,10 years old, attending elementary schools in the metropolitan area of Cagliari, the capital of Sardinia (Italy). The children were divided into two groups according to the level of exogamy. The first group consisted of children of parents born in the same Sardinian municipality and was considered endogamous sensu stricto. The second group included children of parents born in municipalities from different Sardinian linguistic domains and was considered exogamous. The Mann,Whitney test did not reveal significant differences between the two groups of children in the mean rank values of the 36 anthropometric variables considered, with the exception of cephalic circumference in males and chest depth in females. In particular, there were no significant differences for anthropometric variables considered to be indirect indicators of nutritional status: sum of skinfolds, waist/hip ratio, body mass index, total upper arm area, upper arm muscle area, and upper arm fat area. The results indicate that Sardinian children from marriages of different exogamy levels do not differ in body dimensions if they grow up with similar nutritional and socioeconomic conditions. Am. J. Hum. Biol., 2010. © 2010 Wiley-Liss, Inc. [source]

Dairy and milk consumption and child growth: Is BMI involved?

An analysis of NHANES 199
Humans are unique among mammals in that many consume cow's milk or other dairy products well beyond the traditional age of weaning. Milk provides various nutrients and bioactive molecules to support growth and development, and the question arises as to whether this dietary behavior influences growth parameters. There is evidence that milk makes positive contributions to growth in height, but its associations with other aspects of body size, such as body mass index (BMI), are not well-established. National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2004 and multivariate regression analysis were used to test the hypothesis that milk (g) or total dairy product consumption (kJ) is associated with higher BMI percentile among US White, Black, and Mexican-American children of age 2,4 years (n = 1,493) and 5,10 years (n = 2,526). Younger children in the highest quartile of dairy intake had higher BMIs (, = 7.5,8.0; P < 0.01) than those in the lowest two quartiles. Controlling for energy intake eliminated differences between QIV and QI. Among children of 5,10 years of age dairy intake had no relationship to BMI. Young children in the highest quartile of milk intake had higher BMIs than all lower quartiles (, = 7.1,12.8; , = 6.3,11.8 in energy-controlled models; P < 0.05). Among children of 5,10 years of age, those in QIV for milk intake had higher BMIs than those in QII (, = 8.3; , = 7.1 in energy-controlled model; P < 0.01). Controlling for total protein or calcium did not change the results. Milk had more consistent positive associations with BMI than did dairy products, and these were strongest among children of 2,4 years of age. Am. J. Hum. Biol., 2010. © 2010 Wiley-Liss, Inc. [source]

Barrier requirements as the evolutionary "driver" of epidermal pigmentation in humans

Peter M. Elias
Current explanations for the development of epidermal pigmentation during human evolution are not tenable as stand-alone hypotheses. Accordingly, we assessed instead whether xeric- and UV-B-induced stress to the epidermal permeability barrier, critical to survival in a terrestrial environment, could have "driven" the development of epidermal pigmentation. (1) Megadroughts prevailed in central Africa when hominids expanded into open savannahs [,1.5,0.8 million years ago], resulting in sustained exposure to both extreme aridity and erythemogenic UV-B, correlating with genetic evidence that pigment developed ,1.2 million years ago. (2) Pigmented skin is endowed with enhanced permeability barrier function, stratum corneum integrity/cohesion, and a reduced susceptibility to infections. The enhanced function of pigmented skin can be attributed to the lower pH of the outer epidermis, likely due to the persistence of (more-acidic) melanosomes into the outer epidermis, as well as the conservation of genes associated with eumelanin synthesis and melanosome acidification (e.g., TYR, OCA2 [p protein], SLC24A5, SLC45A2, MATP) in pigmented populations. Five keratinocyte-derived signals (stem cell factor,KIT; FOXn1,FGF2; IL-1,, NGF, and p53) are potential candidates to have stimulated the sequential development of epidermal pigmentation in response to stress to the barrier. We summarize evidence here that epidermal interfollicular pigmentation in early hominids likely evolved in response to stress to the permeability barrier. Am. J. Hum. Biol., 2010. © 2010 Wiley-Liss, Inc. [source]

New method for age estimation of developmental defects of enamel formation in living populations

Rhonda Gillett-Netting
Histologically based age of occurrence estimates for developmental defects of enamel (DDE) are raising questions about the continued utility of traditional macroscopic methods; however, the new techniques are not appropriate for use on living populations. This study, using methodology suitable for noninvasive use on living populations, compares assignment of defect timing using a histologically informed macroscopic method (HIMM) versus traditional methodology (TM). For this Southern African population, TM estimates later median age of DDE occurrence than HIMM (Z -score: ,13.565, P < 0.000) and modal age is 1 year earlier. HIMM allows for continued collection of DDE in living populations with the added benefit of more precise timing of enamel development. Accuracy for estimating general stressors during childhood is necessary for construction of diachronic analyses. Am. J. Hum. Biol., 2010. © 2010 Wiley-Liss, Inc. [source]

Sociodemographic determinants of growth among Malian adolescent females

Timothy F. Leslie
In Africa, research concerning the social determinants of poor nutritional status has typically focused on children under 5 years of age and has used defined categorical boundaries based on international reference standards. In this article, stunting and wasting of 1,157 Malian adolescent girls is measured through both categorical and continuous data. The focus on adolescent girls is significant because there is relatively little literature examining this group, and because adolescence marks the time when girls gain greater workload responsibilities, autonomy of food choices, and, as a result of the adolescent growth spurt, require the greatest amount of caloric intake respective to their weight since infancy. To differentiate stunting and wasting causes, a number of socioeconomic, geographic, and demographic factors are explored. The findings suggest that continuous data provides a basis for modeling stunting and wasting superior to utilizing international reference categories. Estimations show that decreasing age, the presence of servants, a greater number of wives in a compound, and residence in a large urban area correlate with improved nutritional status while wealthier families appear to correlate with greater stunting and wasting, and no correlation exists with estimated energy expenditure. Future studies should incorporate continuous data, and the need exists for greater analysis of social determinants of growth indicators among adolescent females. Further, these findings have significant implications in the development of nutrition intervention programs aimed at the vulnerable population in Mali, leading us to conclude that factors beyond socioeconomic indicators such as household structure and location should be more fully examined. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Human birth seasonality and sunshine

David R. CummingsArticle first published online: 20 OCT 200
The environmental light intensity/photoperiod (ELI/PP) hypothesis proposes that the seasonality of human births is primarily associated with seasonal changes in ambient atmospheric luminosity or ELI. This study tests for the presence of increased ELI during the 1 or 2-month period preceding the conceptual month. Monthly birth data for Helsinki, Finland; Kiev, Ukraine; Hanoi, Vietnam; Matlab, Bangladesh; Nashville, Tennessee; Los Angeles, California; Dallas, Texas; Denver, Colorado and Pretoria, South Africa, are correlated (Pearsonian r) to corresponding monthly meteorological data. With the exception of Matlab, birth data are adjusted for conception date, 31-day months, leap years and monthly deviation from an annual mean. Meteorological data are adjusted for a 1,2-month exposure to ELI before conception. From these correlations, Helsinki r = 0.82, Kiev r = 0.80, Hanoi r = 0.93, Matlab r = 0.91, Nashville r = 0.84, Los Angeles r = 0.71, Dallas r = 0.86, Denver r = 0.53, and Pretoria r = ,82. Weakness and strengths of the ELI/PP hypothesis are reviewed using the criteria developed by AB Hill. Substituting meteorological variables for ELI may be a weakness, whereas the specificity of ELI/PP predictions may be a strength. Increased periods of ELI precede increased periods of conceptions. Increased ELI may influence seasonality for chimpanzee, baboon, and humans. Atmospheric pollution may alter the onset of seasonality. Increased ELI may be the initial, but not the singular variable to affect seasonality. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

The reproducibility of ethnic differences in the proportional awake,sleep blood pressure decline among women

Helene M. Van Berge-Landry
A growing body of evidence indicates that African Americans (AA), on average, have a smaller proportional decline in blood pressure (BP) from waking to sleep than European Americans (EA), but this difference is largely based on correlational data from a single assessment day. The persistence of this difference over repeated sampling is not well established. The purpose of this study was to evaluate whether ethnic differences in the awake,sleep BP decline between AA and EA persisted over three monthly assessments. The subjects were 47 AA (age = 39.7 ± 8.7) and 92 EA (age = 37.4 ± 9.2) normotensive women. Subjects had 24-h ambulatory BP monitoring done on midweek workdays at 1-month intervals for three consecutive months. The proportional decline in BP was calculated as follows: (average awake , average sleep)/average sleep. The persistence of ethnic differences was evaluated using repeated-measures ANCOVA and by examining Bland,Altman plots. The ANCOVA results revealed that overall, the proportional decline of AA women was less than that of EA women for both SBP (P < 0.038) and DBP (P < 0.083), consistent with previous research, and that there were also no significant ethnic differences by monthly assessment. Bland,Altman plots revealed that overall and by ethnicity, the proportional decline in BP among individual subjects over the 3 months was also reproducible. These results suggest that the ethnic difference in awake,sleep BP between AA and EA women persists over time and that the awake,sleep decline in BP among individuals, whether AA or EA, is also reproducible. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Boys live dangerously in the womb

Johan G. Eriksson
The growth of every human fetus is constrained by the limited capacity of the mother and placenta to deliver nutrients to it. At birth, boys tend to be longer than girls at any placental weight. Boy's placentas may therefore be more efficient than girls, but may have less reserve capacity. In the womb boys grow faster than girls and are therefore at greater risk of becoming undernourished. Fetal undernutrition leads to small size at birth and cardiovascular disorders, including hypertension, in later life. We studied 2003 men and women aged around 62 years who were born in Helsinki, Finland, of whom 644 had hypertension: we examined their body and placental size at birth. In both sexes, hypertension was associated with low birth weight. In men, hypertension was also associated with a long minor diameter of the placental surface. The dangerous growth strategy of boys may be compounded by the costs of compensatory placental enlargement in late gestation. In women, hypertension was associated with a small placental area, which may reduce nutrient delivery to the fetus. In men, hypertension was linked to the mothers' socioeconomic status, an indicator of their diets: in women it was linked to the mothers' heights, an indicator of their protein metabolism. Boys' greater dependence on their mothers' diets may enable them to capitalize on an improving food supply, but it makes them vulnerable to food shortages. The ultimate manifestation of their dangerous strategies may be that men have higher blood pressures and shorter lives than women. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Short but catching up: Statural growth among native Amazonian Bolivian children

Ricardo Godoy
The ubiquity and consequences of childhood growth stunting (<,2 SD in height-for-age Z score, HAZ) in rural areas of low-income nations has galvanized research into the reversibility of stunting, but the shortage of panel data has hindered progress. Using panel data from a native Amazonian society of foragers-farmers in Bolivia (Tsimane'), we estimate rates of catch-up growth for stunted children. One hundred forty-six girls and 158 boys 2 , age , 7 were measured annually during 2002,2006. Annual , height in cm and in HAZ were regressed separately against baseline stunting and control variables related to attributes of the child, mother, household, and village. Children stunted at baseline had catch-up growth rates 0.11 SD/year higher than their nonstunted age and sex peers, with a higher rate among children farther from towns. The rate of catch up did not differ by the child's sex. A 10% rise in household income and an additional younger sibling lowered by 0.16 SD/year and 0.53 SD/year the rate of growth. Results were weaker when measuring , height in cm rather than in HAZ. Possible reasons for catch-up growth include (a) omitted variable bias, (b) parental reallocation of resources to redress growth faltering, particularly if parents perceive the benefits of redressing growth faltering for child school achievement, and (c) developmental plasticity during this period when growth rates are most rapid and linear growth trajectories have not yet canalized. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Childhood conditions and education as determinants of adult height and obesity among Greenland Inuit

P. Bjerregaard
Height and obesity are risk factors for cardiovascular disease and other physical and mental health conditions. Their association with childhood socioeconomic position has been demonstrated in studies among European and a few third world populations. In a random sample of adult Greenland Inuit (N = 2302) we studied the association between childhood socioeconomic conditions and height as well as prevalence of obesity (BMI , 30) in a cross sectional design. In block recursive graphical independence models, height was associated with mother's place of birth, birth cohort, childhood residence, alcohol problems in childhood home, and education among both men and women. Obesity was associated with mother's place of birth (for men) and with alcohol problems (for women). In General Linear Models, men with an all rural background and no education beyond primary school measured on average 165.1 cm compared with 172.1 cm for men with an all urban background (P < 0.001); women measured 153.9 and 161.1 cm (P < 0.001). Rural-urban differences in prevalence of obesity were not statistically significant. The height differences were considerably larger than between educational groups in European countries and of the same order of magnitude as those reported between men from the 17th century and men from 400 BC in the European and Mediterranean region. The rural-urban gradient in height follows the socioeconomic gradient and may negatively affect cardiovascular risk among the rural Greenlanders, while their physically active lifestyle and high consumption of n-3 fatty acids may counteract this. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Stability of genetic influences on pulmonary function in a longitudinal study of octogenarian twins

Terrie Vasilopoulos
Using data from the first four waves of the OCTO-Twin study (twins 80 + years), the present study investigated the stability and change of genetic and environmental contributions to pulmonary function. Using a genetic simplex model, variance in peak expiratory flow (PEF) at each wave was decomposed into additive genetic and nonshared (specific) environmental factors. Additionally, this analysis distinguished the source of these influences, either from previous waves (transmissions) or from novel influences at each wave (innovations). At each time point (except wave 1), the genetic variance was due to genetic transmissions from prior time points. Conversely, the specific environmental variance in PEF at each time point was mainly due to environmental innovations. These results imply that genetic factors contribute to the stability of pulmonary function over time whereas environmental factors contribute to its change. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

The mean measure of divergence: Its utility in model-free and model-bound analyses relative to the Mahalanobis D2 distance for nonmetric traits

Joel D. Irish
The mean measure of divergence (MMD) distance statistic has been used by researchers for nearly 50 years to assess inter-sample phenetic affinity. Its widespread and often successful use is well documented, especially in the study of cranial and dental nonmetric traits. However, the statistic has accumulated some undesired mathematical baggage through the years from various workers in their attempts to improve or alter its performance. Others may not fully understand how to apply the MMD or interpret its output, whereas some described a number of perceived shortcomings. As a result, the statistic and its sometimes flawed application(s) have taken several well-aimed hits; a few researchers even argued that it should no longer be utilized or, at least, that its use be reevaluated. The objective of this report is to support the MMD, and in the process: (1) provide a brief history of the statistic, (2) review its attributes and applicability relative to the often-used Mahalanobis D2 statistic for nonmetric traits, (3) compare results from MMD and D2 model-free analyses of previously-recorded sub-Saharan African dental samples, and (4) investigate its utility for model-bound analyses. In the latter instance, the ability of the D2 and other squared Euclidean-based statistics to approximate a genetic relationship matrix and Sewall Wright's fixation index using phenotypic data, and the inability of the MMD to do so, is addressed. Three methods for obtaining such results with nonlinear MMD distances, as well as an assessment of the fit of the isolation-by-distance model, are presented. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Selection in utero: A biological response to mass layoffs

Ralph Catalano
Most research describing the biological response to unemployment appears appropriately motivated by clinical or public health concerns and focuses on death, disease, and medical care. We argue that expanding the work to include other outcomes could contribute to basic science. As an example, we use the response to mass layoffs to discriminate between two explanations of low ratios of male to female live births in stressed populations. One explanation asserts that ambient stressors reduce the ratio of males to females conceived. The other argues that the maternal stress response selects against males in utero. We show that selection in utero better explains the observed data. We conclude that human adaptation to the economic environment deserves scrutiny from a wider array of scientists than it now receives. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Population structure and paternal admixture landscape on present-day Mexican-Mestizos revealed by Y-STR haplotypes

J. Salazar-Flores
Mestizos currently represent most of the Mexican population (>90%); they are defined as individuals born in the country having a Spanish-derived last name, with family antecedents of Mexican ancestors back at least to the third generation. Mestizos are result of 500 years of admixture mainly among Spaniards, Amerindians, and African slaves. Consequently, a complex genetic pattern has been generated throughout the country that has been scarcely studied from the paternal point of view. This fact is important, taking into account that gene flow toward the New World comprised largely males. We analyzed the population structure and paternal admixture of present-day Mexican-Mestizo populations based on Y-STRs. We genotyped at least 12 Y-STRs in DNA samples of 986 males from five states: Aguascalientes (n = 293); Jalisco (n = 185); Guanajuato (n = 168); Chiapas (n = 170); and Yucatán (n = 170). AmpF,STR Y-filer and Powerplex-Y® kits were used. Inclusion of North and Central Y-STR databases in the analyses allowed obtaining a Y-STR variability landscape from Mexico. Results confirmed the population differentiation gradient previously noted in Mestizos with SNPs and autosomal STRs throughout the Mexican territory: European ancestry increments to the Northwest and, correspondingly, Amerindian ancestry increments to the Center and Southeast. In addition, SAMOVA test and Autocorrelation Index for DNA Analysis autocorrelogram plot suggested preferential gene flow of males with neighboring populations in agreement with the isolation-by-distance model. Results are important for disease-risk studies (principally male-related) and for human identification purposes, because Y-STR databases are not available on the majority of Mexican-Mestizo populations. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Does second-to-fourth digit length ratio (2D:4D) predict age at menarche in women?

Samuli Helle
Prenatal steroid levels, estimated as the ratio of second-to-fourth digit length (2D:4D), have been related to reproductive success in women, but direct associations between 2D:4D and physiological measures of fertility remain rare. A recent study reported that lower, masculinized right hand 2D:4D was correlated with delayed age at menarche in women. We addressed this question by investigating whether 2D:4D was associated with recalled age at menarche in 282 post-reproductive Finnish women, using Cox regression model that controlled for a woman's sibling composition, urban or rural residence and temporal trend in menarcheal age. We found no evidence that neither the 2D:4D of the right nor the left hand were related to a woman's age at menarche among these Finnish women. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Discrimination, psychosocial stress, and health among Latin American immigrants in Oregon

Heather H. McClure
Chronic psychosocial stress related to discrimination has been shown to be associated with biological measures such as elevated systolic blood pressure (SBP), increased body fat, and higher fasting glucose levels. Few studies have examined these relationships in immigrant populations. The present study recruited a sample of 132 Oregon Latino immigrant adults to investigate the relationships between perceived discrimination and several health measures (blood pressure, body mass index [BMI], and fasting glucose). Results indicate that perceived discrimination stress predicted elevated SBP among men but not among women. Perceived discrimination was significantly higher among obese women than among women of normal BMI. The same pattern was not observed for men. Further, a strong trend relationship was detected: the higher women's reported discrimination stress, the higher their fasting glucose levels. Again, this pattern was not observed for men. These results suggest that chronic psychosocial stress plays an important role in disease risk among Latin American immigrants, and that male and female immigrants may have distinctive physiological responses. If confirmed, these findings may have important clinical and public health implications for chronic disease prevention among Latinos. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Reproductive development and parental investment during pregnancy: Moderating influence of mother's early environment

David A. Coall
The association between a woman's age at menarche and the birth weight of her children is highly variable across human populations. Life history theory proposes that a woman's early environment may moderate this association and thus account for some of the variation between populations. According to one life history theory model, for individuals who develop in a childhood environment of high local mortality rates (experienced subjectively as psychosocial stress), it can be adaptive to mature earlier, have more offspring during their reproductive lifetime, and reduce investment in each offspring. In an environment of low psychosocial stress, however, it may be adaptive to mature later, have fewer offspring, and invest more in each. In this study, birth weight and proportionate birth weight (neonate's birth weight as a percentage of its mother's prepregnancy weight) were used as measures of parental investment during pregnancy. In a sample of 580 first-time mothers, we tested the hypothesis that the psychosocial stress experienced as a child would moderate the association between age at menarche and investment during pregnancy. We found that earlier menarche in those women who experienced stressful life events before 15 years of age was associated with a lower birth weight and proportionate birth weight. Conversely, in those who reported no childhood stressors, earlier menarche was associated with increased birth weight and proportionate birth weight. Our data suggest that the moderating influence of the childhood psychosocial environment on the association between age at menarche and parental investment throughout gestation operates in a dose-dependent manner. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Autosomal and X chromosome Alu insertions in Bolivian Aymaras and Quechuas: Two languages and one genetic pool

Magdalena Gayà-vidal
Thirty-two polymorphic Alu insertions (18 autosomal and 14 from the X chromosome) were studied in 192 individuals from two Amerindian populations of the Bolivian Altiplano (Aymara and Quechua speakers: the two main Andean linguistic groups), to provide relevant information about their genetic relationships and demographic processes. The main objective was to determine from genetic data whether the expansion of the Quechua language into Bolivia could be associated with demographic (Inca migration of Quechua-speakers from Peru into Bolivia) or cultural (language imposition by the Inca Empire) processes. Allele frequencies were used to assess the genetic relationships between these two linguistic groups. Our results indicated that the two Bolivian samples showed a high genetic similarity for both sets of markers and were clearly differentiated from the two Peruvian Quechua samples available in the literature. Additionally, our data were compared with the available literature to determine the genetic and linguistic structure, and East,West differentiation in South America. The close genetic relationship between the two Bolivian samples and their differentiation from the Quechua-speakers from Peru suggests that the Quechua language expansion in Bolivia took place without any important demographic contribution. Moreover, no clear geographical or linguistic structure was found for the Alu variation among South Amerindians. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Metric and nonmetric dental variation and the population structure of the Ainu

Tsunehiko Hanihara
Gene flow and genetic drift are important factors affecting geographic variations in human phenotypic traits. In the present study, the effects of gene flow from an outside source on the pattern of within- and among-group variation of the Ainu from Sakhalin Island and three local groups of Hokkaido are examined by applying an R-matrix approach to metric and nonmetric dental data. The comparative samples consist of their ancestral and neighboring populations, such as the Neolithic Jomon, the subsequent Epi-Jomon/Satsumon, the Okhotsk culture people who migrated from Northeast Asia to the northeastern part of Hokkaido during a period 1600,900 years B.P., and modern non-Ainu Japanese. The results obtained by using the census population sizes of the regional groups of the Ainu as an estimate of relative effective population size suggest the possibility of an admixture between the Okhotsk culture people and the indigenous inhabitants in Hokkaido, at least in the coastal region along the Sea of Okhotsk. Such gene flow from Northeast Asian continent may have exerted an effect on the genetic structure of the contemporary Ainu. The present findings indicate that the population structure, as represented by genetic drift and gene flow, tend to be obscured in the results obtained by standard statistical methods such as Mahalanobis' generalized distance and Smith's MMDs. The present extension of the R-matrix approach to metric and nonmetric dental data provide results that can be interpreted in terms of a genetically, archaeologically, and prehistorically suggested pattern of gene flow and isolation. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Birthweight and paternal involvement predict early reproduction in British women: Evidence from the National Child Development Study

Daniel Nettle
There is considerable interest in the mechanisms maintaining early reproduction in the most socioeconomically disadvantaged groups in developed countries. Previous research has suggested that differential exposure to early-life factors such as low birthweight and lack of paternal involvement during childhood may be relevant. Here, we used longitudinal data on the female cohort members from the UK National Child Development Study (n = 3,014,4,482 depending upon variables analyzed) to investigate predictors of early reproduction. Our main outcome measures were having a child by age 20, and stating at age 16 an intended age of reproduction of 20 years or lower. Low paternal involvement during childhood was associated with increased likelihood of early reproduction (O.R. 1.79,2.25) and increased likelihood of early intended reproduction (O.R. 1.38,2.50). Low birthweight for gestational age also increased the odds of early reproduction (O.R. for each additional s.d. 0.88) and early intended reproduction (O.R. for each additional s.d. 0.81). Intended early reproduction strongly predicted actual early reproduction (O.R. 5.39, 95% CI 3.71,7.83). The results suggest that early-life factors such as low birthweight for gestational age, and low paternal involvement during childhood, may affect women's reproductive development, leading to earlier target and achieved ages for reproduction. Differential exposure to these factors may be part of the reason that early fertility persists in socioeconomically disadvantaged groups. We discuss our results with respect to the kinds of interventions likely to affect the rate of teen pregnancy. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Genetic composition of Brazilian population samples based on a set of twenty-eight ancestry informative SNPs

Tulio C. Lins
Ancestry informative SNPs can be useful to estimate individual and population biogeographical ancestry. Brazilian population is characterized by a genetic background of three parental populations (European, African, and Brazilian Native Amerindians) with a wide degree and diverse patterns of admixture. In this work we analyzed the information content of 28 ancestry-informative SNPs into multiplexed panels using three parental population sources (African, Amerindian, and European) to infer the genetic admixture in an urban sample of the five Brazilian geopolitical regions. The SNPs assigned apart the parental populations from each other and thus can be applied for ancestry estimation in a three hybrid admixed population. Data was used to infer genetic ancestry in Brazilians with an admixture model. Pairwise estimates of Fst among the five Brazilian geopolitical regions suggested little genetic differentiation only between the South and the remaining regions. Estimates of ancestry results are consistent with the heterogeneous genetic profile of Brazilian population, with a major contribution of European ancestry (0.771) followed by African (0.143) and Amerindian contributions (0.085). The described multiplexed SNP panels can be useful tool for bioanthropological studies but it can be mainly valuable to control for spurious results in genetic association studies in admixed populations. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]

Nutritional status, body composition, and intestinal parasitism among the Mbyá-Guaraní communities of Misiones, Argentina

M.L. Zonta
Indigenous communities in Argentina represent socially and economically neglected populations. They are living in extreme poverty and environmental degradation conditions. New information about health status and socio-environmental features is urgently needed to be applied in future sanitary policies. Present study describes the nutritional status, body composition, and intestinal parasitism among Mbyá-Guaraní children from three communities in the Misiones Province. Anthropometric parameters were analized for 178 individuals (aged 1,14). Data were transformed to z -scores using NHANES I and II. Stunting showed the greatest prevalence (44.9%). Children were found to have low arm circumference and low arm muscle area, although with tricipital skinfold value near to the reference. They also tend to have shorter than normal lower limbs. Fecal samples and anal brushes (for Enterobius vermicularis) were collected in 45 children (aged 1,13). Ritchie's sedimentation and Willis' flotation techniques were used to determine parasitoses. Ninety five percent of children were infected with at least one species and 81.4% were polyparasitized. The higher prevalences corresponded to Blastocystis hominis, hookworms (Ancylostoma duodenale/Necator americanus), and Entamoeba coli. Associations occurred between hookworms with B. hominis/E. coli and B. hominis with nonpathogenic amoebas. Thirty nine percent of the children with stunting presented B. hominis, Strongyloides, and hookworms. Our results indicate that this indigenous population is subjected to extreme poverty conditions and is one of the most marginalized in this country. Severe growth stunting and parasitic infection are still quite common among Mbyá children affecting about half of them along with significant changes in body composition and proportions. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source]