Opportunity for natural selection and gene flow in an isolated Zapotec-speaking community in southern Mexico in the throes of a secular increase in size

Our object in this paper is to analyze the opportunity for natural selection and gene flow in an isolated Zapotec-speaking community in the valley of Oaxaca, southern Mexico, that is undergoing a secular increase in body size. Surveys were conducted in the community in 1968, 1978, and 2000, including anthropometric and census data. No secular change was found in the growth status of schoolchildren and adult height between 1968 and 1978; subsequently, major secular gains in height occurred among children and adolescents between 1978 and 2000. The 1978 household data were used to compute gene flow (3.3%) and opportunity for selection intensity (I = 1.312). Migration and other demographic information was obtained from household census data for 1978 and 2000, and mortality information was extracted from community records and archives. These data were used to compute gene flow and opportunity for natural selection. Gene flow increased from 3.3% to 4.7% and intensity of natural selection decreased from 1.312 to 0.272 from 1978 to 2000. Variance in fertility increased slightly over time (12.25 to 13.69). Opportunity for selection was dominant during the prereproductive period in 1978, but approached 0 for the mortality component in 2000, resulting in a marked decrease in the mortality component (Im) of selection (0.626 and 0.019, respectively) and total opportunity for selection (I = 1.312 and 0.272, respectively). Secular increase in height and markedly decreased opportunity for natural selection (1) were associated with better health and nutritional conditions. Genotype-environment interaction and environmental influences are apparently the predominant causes of the secular trend. If natural selection plays a role in causing the secular trend, it is a small one.     

Adult stature and age at menarche in Zapotec-speaking communities in the Valley of Oaxaca,Mexico, in a secular perspective

Adult stature and the age at menarche among individuals from Zapotec-speaking communities in the Valley of Oaxaca in southern Mexico are considered in a secular perspective. Four sets of observations are utilized: (1) adult stature in males and females from five rural communities; (2) age at menarche in adult women and school girls from a single rural community; (3) earlier studies of adult stature in the Valley of Oaxaca; and (4) estimated stature from long bones excavated in various archaeological sites in the Valley of Oaxaca. There were no significant differences among the five communities for stature; hence, the data were pooled for analysis and comparison. Results of linear regression of stature and stature adjusted for the estimated effects of aging after 30 years of age on year of birth indicate negligible secular changes in either sex. Comparisons with statures from earlier surveys, the earliest dates to 1899, also indicate negligible changes. When adult women are grouped according to age, there are no differences in mean ages at menarche between the older and younger women. Mean age at menarche for the total adult sample is 14.53 ± 0.08 years, which compares favorably with the probit estimate for school girls, 14.70 ± 0.32 years. These results thus suggest virtually no secular change in adult size and maturity of the Zapotec-speaking population in the Valley of Oaxaca over the past 80 years. Differences in stature between contemporary populations and estimated statures from long bones from several archaeological sites in Oaxaca are small, and thus suggests little secular change over the past one to two–thousand years.     

Brachycephalization in Japan has ceased

Somatometric data are presented which show that the rapid brachycephalization in Japan has recently ceased. The causes of brachycephalization are investigated in relation to the secular change in height. Increases in head breadth have been the main cause of brachycephalization, and its pattern of secular change is very similar to that in height. Associations between head breadth, height, and year of birth were examined by partial correlation coefficients and through a comparison of students and the general population. Brachycephalization is thought to result from increases in the growth rate for head breadth caused by improvements in nutritional levels, as seen in increases in height. Increases in height over the last 100 years have been accompanied by brachycephalization in Japanese and Koreans, but by debrachycephalization in many European populations. Increases in lateral growth in Asian heads may be related to the facial flatness which is characteristic to northern Mongoloid populations.     

Secular Trends in Measures of Cephalo-Facial Traits among Bengalee Boys Aged 7.0–16.0 Years from Kolkata between 1982–1983 and 1999–2001

While a large number of studies on secular trends have been performed on measures of stature, weight, trunk and limb dimensions, subcutaneous fatness and body composition, etc., less attention has been paid to cephalo-facial traits. This study reports on secular trends in five cephalo-facial traits (head length, head breadth, head circumference, bizygomatic breadth and morphological facial height) and two indices (cephalic index and facial index) in Bengalee Hindu boys between ages 7.0 and 16.0 years. The data set comes from two cross-sectional growth surveys carried out among the students of one particular Kolkata (formerly Calcutta) boys school with an interval of about 20 years (1982–1983 and 1999–2001). Identical protocol with respect to sampling, data collection, measuring technique and data analysis has been followed in both surveys. Except for morphological facial height (which showed negative secular trends), the other four cephalo-facial traits showed positive secular trends with varying magnitudes over the two decades. Cephalic index did not reveal any consistent pattern of change, while facial index showed a declining trend in the later survey.     

Age and secular factors in the stature of adult Zapotec males

Age and secular factors in adult stature were investigated in a sample of 111 Zapotec-speaking males from Oaxaca, Mexico. Comparisons with earlier studies showed no clear evidence of a secular trend. The increase in stature due to age and secular factors was approximately 0.07 cm per year (significant, p < 0.05). When stature was adjusted for the estimated age effects, the estimated secular increase was 0.03 cm per year (not significant). By this analysis a secular trend in adult stature of the magnitude noted for industrialized countries apparently does not occur in developing areas.     

Socioeconomic variation in estimated growth velocity of schoolchildren from a rural, subsistence agricultural community in southern Mexico

Socioeconomic variation in estimated growth velocities (annual growth increments) of several anthropometric dimensions was considered in schoolchildren from a rural, subsistence agricultural community in the Valley of Oaxaca in southern Mexico. The children (114 males, 99 females), 6-13 years of age, were measured twice, approximately one year apart. Annual growth increments were computed by subtracting measurements taken in the fall of 1978 from those taken in the fall of 1979. Information on household land holdings and appliances and parental occupation was used to compute an index of socioeconomic status (SES). Analysis of annual increments among upper SES (65 males, 45 females) and lower (49 males, 54 females) children indicated negligible differences. The results suggest that growth deficits evident in the children at school age occurred in infancy and early childhood so that there was little, if any, SES variation in growth rate at the school ages.     

Effects of interracial crosses on cephalometric measurements

The effects of race and interracial crossing were examined on six cephalometric measurements among 9,912 schoolchildren in Hawaii. The measurements studied were face height, bizygomatic diameter, bigonial diameter, head breadth, head length, and cephalic index. Racial effects were studied in terms of general racial effect, maternal effect, and hybridity and recombination effects based on a model of diallel cross. Generally, Chinese, Japanese, Koreans, and Filipinos were characterized by longer lateral and smaller anterior-posterior dimensions relative to Caucasians. Maternal effects appeared to be present in the measures of lateral dimension. No clear effects of hybridity and recombination were seen except for bizygomatic diameter, which appears to behave as a partial dominant trait. The racial mean of bizygomatic diameter, or the ratio of this measure to head length, were found to have a relationship with the racial incidences of cleft lip with or without cleft palate.     

Secular change in heights of indigenous adults from a Zapotec‐speaking community in Oaxaca,southern Mexico

Secular change in adult height of residents in a rural indigenous community in the Valley of Oaxaca was evaluated. Subjects were measured in 1971 (49 males, 26 females 19–70 years), 1978 (128 males, 124 females 19–82 years) and 2000 (155 males, 255 females 19–89 years). Heights were adjusted for estimated loss with age using two protocols; height at 21 years of age was also estimated. The effects of age and secular factors on measured and adjusted heights were evaluated through segmented linear regressions for three birth periods, <1930, 1930 through 1959 and ≥1960 which approximate significant periods in Mexican history. Secular increase in height occurred but estimated rates varied over time and between sexes. Males born before 1930 showed a secular increase in height but females did not. Adults of both sexes born 1930–1959 showed secular gains and estimated rates did not differ. The secular gain in height continued among those born 1960 and later and estimated rates were similar in both sexes. Estimated height at 21 years of age increased in males (not significant) but not in females born before 1930, showed little or no change in those born between 1930‐1959, and increased (not significant) in those born 1960 and later. Combining observations on adults with those for youth in the community indicated several phases of secular change in height that varied with years of birth. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

Results of the study of selected head measurements of Jena children]

Secular changes of head measurements (frontal breadth, bizygomatic breadth, bigonial breadth, auricular height, morphological facial height, lower face height) are analysed. The data are based on the Jena anthropological investigations of school children from 1975 and 1985. The inclusion of the data of the Jena longitudinal study carried out since 1985 allows an analysis of the further secular trend. Noticeable changes are proved in most of the analysed traits (frontal breadth, bigonial breadth, auricular height, morphological facial height, lower face height) between 1975 and 1985. The vertical measurements show greater percentage differences than the horizontal measurements, which, among other things, results in a relative narrowing of the face. In some head measurements (frontal breadth, bigonial breadth, auricular height) the trends continue after 1985. The secular trends show no obvious connection with the temporal acceleration of the dentition in the probands of the longitudinal study. However, a connection seems to be possible between the accelerated puberal growth spurt of the body height and the puberal growth spurt in some head dimensions.     

Age effects and secular trend in a cross-sectional sample: application to four head dimensions in Belgian adults

If longitudinal studies represent the more direct way to analyze modifications resulting from aging, often for obvious reasons cross-sectional samples can also be used for this purpose. But in this case differences between age groups cannot be identified with the effects of age only; they can also be attributed to the effects of a secular trend. It is the aim of this study to show, using four cephalic dimensions and a cross-sectional sample, the need to take into account the effect of a secular trend when the age effect is studied. In 1985 a study of head and facial measurements of 182 Belgian men, aged 25-54 years, was carried out. A simple comparison between different age groups (F tests) revealed significant differences for head breadth and facial breadths. However, no difference for head length was observed. The amplitude of the secular trend in the Belgian population is already known; thus an easy calculation is proposed to define the effects of the age factor. For head breadth the whole difference seems to be the result of the important decrease of secular trend, whereas the global increase observed for the bizygomatic and bigonial breadths results in part from the decrease resulting from the secular trend and in part from the increase resulting from the age effect.     

Changes in BMI and the prevalence of overweight and obesity in children and adolescents in Cracow, Poland, 1971-2000.

The aim of this study is to examine changes in prevalence of overweight and obesity, using International Obesity Task Force criteria, in three cohorts of children and youth living in Cracow, Poland, in 1971, 1983 and 2000. Rates of overweight and obesity doubled among boys and girls, from 7.5% and 6.5% in 1971, to 15.2% and 11.8% in the year 2000. The greatest increases in prevalence occurred in the youngest age groups (7-12 years for boys and 7-10 years for girls), increases being less extensive among adolescents, and lowest of all in the oldest age groups (16-18 years in boys and 14-18 years in girls). The absence of a positive secular trend in BMI among adolescent females relative to males may be due to sociocultural pressures associated with transition to a free market economy in Poland. The extent to which girls attempt to achieve the ideal body, as portrayed by media and society more generally, increases across adolescence.     

The phenomenon of debrachycephalization in Jena school children

Head measurements are performed within the anthropological investigations of school children from Jena (Germany) since more than 5 decades (1944-1995). Here we report on secular changes of the head length, the head breadth and the cephalic index. The head circumference, measured in 1985 and in 1995, is included in the analysis. Head length and head breadth show a contrary development over the whole period: the average length of the head increases between the consecutive investigations, whereas the breadth of the head decreases continuously between the separate investigations. As a consequence the cephalic index decreases in boys and girls for about 8 units since 1944. In this way a secular change of the shape of the head in the sense of debrachycephalisation can be proved in Jena school children. The head circumference, however, remains nearly constant between 1985 and 1995. Possible causes of this process of debrachycephalisation are focussed in this article.     

Changes in BMI and the prevalence of overweight and obesity in children and adolescents in Cracow, Poland, 1971–2000

The aim of this study is to examine changes in prevalence of overweight and obesity, using International Obesity Task Force criteria, in three cohorts of children and youth living in Cracow, Poland, in 1971, 1983 and 2000. Rates of overweight and obesity doubled among boys and girls, from 7.5% and 6.5% in 1971, to 15.2% and 11.8% in the year 2000. The greatest increases in prevalence occurred in the youngest age groups (7–12 years for boys and 7–10 years for girls), increases being less extensive among adolescents, and lowest of all in the oldest age groups (16–18 years in boys and 14–18 years in girls). The absence of a positive secular trend in BMI among adolescent females relative to males may be due to sociocultural pressures associated with transition to a free market economy in Poland. The extent to which girls attempt to achieve the ideal body, as portrayed by media and society more generally, increases across adolescence.     

Prevalence of obesity in elementary schoolchildren living in Northeast Attica, Greece

Objective: To assess the prevalence of obesity and obesity trend in schoolchildren living in Northeast Attica, Greece. Research Methods and Procedures: Mean (standard deviation) and median weight and BMI were calculated in 4131 (2054 boys and 2077 girls) 6‐ to 11‐year‐old Greek schoolchildren living in Northeast Attica between November 2003 and April 2004. Two hundred thirty‐six (95 boys, 141 girls) immigrant children also participated in the study. The secular trend for obesity was determined comparing our data with those of a similar study performed in 1994. Results: Of boys, 27.8% were overweight, and 12.3% were obese. For girls, the corresponding values were 26.5% for overweight and 9.9% for obesity. There was an increase in the prevalence of overweight and obesity in the last 10 years in both sexes. For boys, overweight increased by 4.2% and obesity by 2.9%, whereas, for girls, overweight increased by 3.8% and obesity by 1.6%. Overweight and obesity were less prevalent in the immigrant children compared with their Greek peers. For immigrant boys, overweight was 15.9% and obesity was 7.9%, and for immigrant girls, overweight was 15.2% and obesity was 8.7%. Discussion: Greek schoolchildren living in Northeast Attica present a high prevalence of overweight and obesity and a positive secular change in the prevalence of obesity.     

Family resemblance for cranio-facial measurements in Velanti Brahmins from Andhra Pradesh, India

Maximum likelihood estimates of familial correlations are presented for 12 cranio-facial measurements taken on 399 nuclear families from Southern India. Marital resemblance is significantly different from zero for head circumference, head breadth, minimum frontal breadth, bizygomatic breadth, total facial height, and nasal height, but not for bigonial breadth, nose breadth, nose depth, or ear dimensions. All other familial correlations are significantly greater than zero except for the father-daughter correlation for nasal depth. Path analysis with a TAU transmission model with sex effects reveals that family resemblance for head circumference, head length, bigonial breadth, total facial height, and nasal height, but not for bigonial breadth, nose breadth, nose depth, or ear dimensions. All other familial correlations are significantly greater than zero except for the father-daughter correlation for nasal depth. Path analysis with a TAU transmission model with sex effects breadth, and sex effects in transmission were found for head breadth and nose dimensions. Sex effects in this sample may be due to the fact that different anthropometrists were used for male and female subjects.     

Gene flow and variation in stature and craniofacial dimensions among indigenous populations of southern Mexico, Guatemala, and Honduras

Populations with histories of outbreeding tend to be taller even in the face of seemingly unchanged health and nutritional circumstances, while inbreeding generally results in a negative correlation between body dimensions and level of inbreeding. Populations that have experienced a positive secular trend in stature and maturation typically have histories of higher outbreeding rates in combination with improved nutritional, health, and economic conditions, suggesting a genetic-environment interaction. In general, Middle American Indians have not experienced a secular trend in stature, nor a substantial increase in their standard of living, but they have experienced varying degrees of admixture with Spanish and African populations since the Spanish Conquest. The relationship between estimated gene flow and variation in several anthropometric dimensions is thus considered in indigenous Mesoamerican populations. Available data on height, sitting height, craniofacial dimensions, and admixture rate of Indian populations from southern Mexico, Guatemala, and Honduras were assembled from the literature. The population mean data on 3,371 adults from 23 populations for males and 18 for females were analyzed by regression with anthropometry as the dependent variable, and log10 of admixture as the independent variable. Admixture was less than or equal to 28.9% in this study and is suggestive of a primarily traditional Indian cultural and economic base. The results suggest that populations with higher admixture tend to be taller, and that the increase in stature is due to greater subischial length in both sexes. A decrease in nasion-menton height, and an increase in nasal breadth, nasal height, and the nasal index is suggested for the dimensions of the craniofacial complex.(ABSTRACT TRUNCATED AT 250 WORDS)     

中国石龙子个体发育过程中头部两性异型和食性的变化

许多动物呈现个体大小、局部形态特征 (头部大小 )和体色的两性异形[5,14 ,15,2 1,2 2 ] 。 Darwin[12 ] 认为两性谋求各自最大的繁殖利益导致了两性异形 ,因此两性异形是性选择压力作用的结果。自 Darwin以来 ,许多同行认为性选择压力和非性选择压力均能导致动物的两性异形 ,两种选择压力在不同的动物中所起的作用是不同的 [2～ 5,7,10 ,16,2 1～ 2 6] 。性选择压力导致的两性异形与繁殖成功率直接有关。非性选择压力导致的两性异形与繁殖成功率无关或无直接的关系 ,如两性寿命的差异 [13 ]、两性食性的分离 [6,2 1]和两性分配用于生长的…     

38年来济南、青岛儿童少年生长的长期变化

本文分析了济南、青岛1962—2000年7—18岁儿童少年生长发育的长期变化趋势。38年间,济南市7—18岁男女生身高平均增长15 48cm(男)、12 09cm(女),体重平均增长15 76kg(男)、10 01kg(女),胸围平均增长7 88cm(男)、4 10cm(女);青岛市7—18岁男女生身高平均增长17 12cm(男)、13 19cm(女),体重平均增长16 98kg(男)、10 46kg(女),胸围平均增长6 72cm(男)、3 05cm(女)。青岛市男女生身高的增长幅度显著大于济南。     

Craniometric allometry in the thicktailed bushbabyOtolemur Crassicaudatus

Static adult craniometric allometry was evaluated in a sample of 66Otolemur crassicaudatus skulls (34 males, 32 females). Although cranial measures were equally well correlated to skull length in males and females, there were noteworthy differences in the exponential values between the sexes. These results underlined the need for caution when allometric analyses are based on pooled data. From the cranial allometric analyses it is concluded that the longer the skull, the shorter and the narrower the maxilla, and the broader the bizygomatic distance. Although cranial length increased proportionately to the increase in skull length, the cranial width in females was positively allometric whilst in males it was negatively allometric. Allometric analyses of mandibular dimensions suggest that larger animals will have proportionately longer mandibulae, which will, in turn, be relatively wider across the gonia, yet shallower behind the first molars. It is postulated that the disproportionate widening of the zygomata might be related to the widening across the gonia.     

从体质特征看中国南方汉族的人种归属

2009年至2012年研究组调查了中国南方汉族15154例(男性为7340例,女性为7814例)的身高、体重和16项测量指标,并计算出12项指数,将南方汉族与蒙古人种北亚类型族群、南亚类型族群及东亚类型族群的韩国人、日本人进行了比较。结果显示:1)南方汉族头面部主要指标介于北亚、南亚类型族群之间;南方汉族男性更接近于北亚类型族群,而南方汉族女性比男性头面部特征更接近南亚类型族群。2)南方汉族男性头部的长、宽、高、围度小于东亚类型族群,面部比韩国人、日本人狭窄;南方汉族女性头的长、宽、围度、下颌角间宽值小于韩国人、日本人,头较高,面部比韩国人、日本人狭窄。南方汉族男性、女性与韩国人、日本人体质差异较大。3)聚类分析结果提示,中国南方汉族与韩国人、日本人体质差异较大。南方汉族男性体质相对接近于北亚类型族群,女性体质介于北亚、南亚类型族群之间。华南汉族体质在南方汉族中有一定的特殊性。