Craniofacial dimensions in children in rural Oaxaca, southern Mexico: secular change, 1968-2000

The objective of this investigation was to analyze the underlying cause(s) of secular changes in craniofacial dimensions among indigenous children in an isolated community in Oaxaca, southern Mexico, between 1968-2000. Subjects were schoolchildren resident in a rural, agrarian, Zapotec-speaking community in the Valley of Oaxaca, previously characterized as mildly-to-moderately undernourished with growth-stunting in 1968 and 1978. In 2000, children had experienced a secular increase in height compared with two prior growth surveys. Four craniofacial dimensions (head length, head breadth, and bizygomatic and bigonial breadths) were measured during anthropometric surveys of schoolchildren aged 6-13 years in 1968, 1978, and 2000. Cephalic and zygomandibular indices were calculated. Samples by survey were: 1968, 151 males and 157 females; 1978, 179 males and 184 females; and 2000, 180 males and 186 females. The analysis was based on a total of 1,037 children. Multivariate analysis of covariance was used to assess secular trend effects, with height, age, and age2 as covariates by sex. Over the interval of 32 years, significant secular changes occurred in craniofacial dimensions and one index: 1) head length was shorter in boys and girls; 2) bizygomatic breadth was narrower in boys and girls; 3) head breadth increased over time only among girls; 4) brachycephalization increased significantly in a linear manner among both sexes; and 5) the zygomandibular index decreased significantly only in boys. Thus, the cranial complex remodeled to a shorter head length, both relatively (brachycephalization) and absolutely. Remodeling over time also resulted in a narrower face, with the midface changing at about the same rate as the lower face (i.e., mandible). Secular changes are generally recognized as multifactorial. Changes in the cephalic index and cranium over time in schoolchildren in an isolated rural agrarian Zapotec-speaking community in the Valley of Oaxaca suggest that the underlying forces for the secular change are associated: 1) decreased food (maize) coarseness or grit content (masticatory stress), and 2) relaxed natural selection, resulting in 3) a greater role for developmental plasticity.     

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.     

Opportunity for natural selection in a Basque population and its secular trend: evolutionary implications of epidemic mortality

Analysis of the interaction between mortality patterns and opportunity for natural selection could help to elucidate potential evolutionary implications of epidemic mortality. In this paper secular trends are studied in relation to Crow's index (It) and its components of mortality (Im) and fertility (If), using parish records for family reconstitution in a Basque population. A principal components analysis (91% of the variance accounted for) showed marked quantitative and qualitative variations of Im and If depending on the stage of demographic transition of the population analyzed: In pretransitional societies the opportunity for natural selection is determined mainly by differential prereproductive mortality, whereas in posttransitional societies selection resulting from differential fertility plays a key role. The highest values for the mortality component (range 0.81-1.26) and for the relative contribution of Im, to It (range 47.1-57.2%) were observed in periods with a high incidence of infectious diseases and when the most severe mortality crises were detected (1830-1859, 1860-1889, and 1890-1919). A differential incidence of epidemic mortality was also found at prereproductive ages (before 16 years) and at reproductive ages (16-45 years), which provides strong support for the idea of the long-term genetic consequences of mortality crises.     

Selection intensities in menopausal and permanent contraceptor women of a rural population in India

Changing fertility and mortality patterns due to socioeconomic forces have a profound effect on natural selection in human populations. The opportunity for selection was estimated in the rural population of Visakhapatnam District, Andra Pradesh, India, in 1979. A total of 1570 women were interviewed, 1544 among them had ever been pregnant. Data were analyzed to compute fertility and mortality components of the population. The index of total selection was found to be low. Selection in relation to birth control reveals that opportunity for selection is lower among women who completed their fertility by family planning methods than in women who completed their fertility by attaining menopause. Further, the results showed that differential fertility and mortality make equal contributions to the total measure of selection in both groups, whereas in developed countries like the US the mortality component contributes only a small fraction to the total index, due to improved health conditions.     

Household Epidemics: Modelling Effects of Early Stage Vaccination

A Markovian susceptible → infectious → removed (SIR) epidemic model is considered in a community partitioned into households. A vaccination strategy, which is implemented during the early stages of the disease following the detection of infected individuals is proposed. In this strategy, the detection occurs while an individual is infectious and other susceptible household members are vaccinated without further delay. Expressions are derived for the influence on the reproduction numbers of this vaccination strategy for equal and unequal household sizes. We fit previously estimated parameters from influenza and use household distributions for Sweden and Tanzania census data. The results show that the reproduction number is much higher in Tanzania (6 compared with 2) due to larger households, and that infected individuals have to be detected (and household members vaccinated) after on average 5 days in Sweden and after 3.3 days in Tanzania, a much smaller difference.     

Secular change in growth of native children and adolescents at high altitude Huancayo,Peru (3,280 meters)

Stature and weight of native children, adolescents, and adults at Huancayo, Peru (3,280 meters), were measured in 1977, 1978, and 1982 and compared with mean statures and weights reported in previous studies. The data indicate that in Huancayo there has been a secular increment in child stature, sitting height, and weight from 1937 to 1978–1982. The observed changes in stature are related to a proportionally greater increment in leg length relative to trunk length. It is concluded that the observed secular increase in body size reflects changes in the standard of living and a greater influx of nonnative populations, which are usually characterized by greater stature than natives.     

Biological fitness and action opportunity of natural selection in an urban population of Cuba: Plaza de la Revolución, Havana

This paper describes the biological fitness of an urban population of Havana city, Plaza de la Revolución, which has the lowest fertility and the highest demographic ageing in Cuba. The aim is to assess the biological fitness of this community through the indexes of action opportunity of natural selection, to determine its evolutionary pattern and the influence of its socio-cultural peculiarity. Demographic data were obtained from the reproductive histories of 1200 women between the ages of 55 and 64. Data concerning mortality and surviving offspring from the first embryonic stages until age of reproduction were also collected. In order to measure the level of biological fitness two indexes were used: the Crow index of action opportunity of natural selection and the corrected index proposed by Johnston and Kensinger, which takes into account prenatal mortality. This corrected index was calculated including and excluding induced abortions in order to evaluate the contribution of these to biological fitness. When only postnatal mortality was considered, the results showed an evolutionary pattern similar to that of developed countries, based on low mortality and fertility. However, when prenatal mortality was taken into account, biological fitness decreased and the corrected index of natural selection was 4.5 times higher than when miscarriages and fetal deaths were not considered. Moreover, this corrected index was 2.65 times higher when induced miscarriages were considered, indicating the large decrease in biological fitness as a result of the current reproductive behaviour of frequent induced abortion.     

Mortality changes in a polish rural community (1350–1972) and estimation of their evolutionary significance

Changes in the mortality profiles of the population of 13 villages in central Poland have been studied for the medieval and nineteenth-century periods. Three measures, derived from the demographic data, were analyzed within an evolutionary context: (1) I_m, the opportunity for selection through differential mortality, (2) R_pot, the potential gross reproductive rate, and (3) I_bs, the index of biological state. Changes in these indicators over time denote sharp differences in the opportunity for natural selection through differential mortality. The greatest changes are associated with technological and organizational transformations of the social system, especially during the first half of the nineteenth century.     

Estimation of secular trends in adult height, and childhood socioeconomic circumstances in three Eastern European populations

The objective of these analyses was to estimate the strength and direction of secular trends in adult height and childhood socioeconomic circumstances in eight towns in three Eastern European countries in the mid-20th century, and to assess the extent to which childhood conditions might explain the height differences. We used cross-sectional data from the baseline survey of the Health, Alcohol and Psychosocial factors in Eastern Europe (HAPIEE) study, conducted in 2002-2005. The study examined 24,012 men and women born between 1933 and 1957, randomly selected from the general populations of Novosibirsk (Russia), Krakow (Poland) and six towns of the Czech Republic. To allow for age-related height loss we estimated maximum attained height. Parental education and household item ownership at age 10 were used as markers of childhood socioeconomic conditions. In all 5-year birth cohorts, Novosibirsk men and women were shortest. There were positive and statistically significant secular trends in childhood conditions and in maximum adult height. Adjustment for childhood conditions explained about one third of the trend in height. There appeared to be a small reduction in height of persons born during the Second World War which was, however, only significant in Novosibirsk. These results suggest that secular trends in height mirror, but are not wholly explained by, trends in socioeconomic circumstances in early life.     

Demography and computer simulation in historic village population reconstruction

"Demographic anthropology has given rise to methodological advances in the analysis of single community populations. However, the obstacles of small data bases and incomplete vital-event registration remain. This paper details one approach to these problems; the principles of community demography are incorporated with computer simulation methodology, with the goals of validating the internal consistency of and determining demographic secular trends from data commonly utilized in anthropological investigations." The approach is tested on data for the 250 inhabitants of Old Crow Village, Yukon Territory, Canada, in 1978.     

Genetic versus census estimators of the opportunity for sexual selection in the wild

Abstract The existence of a direct link between intensity of sexual selection and mating-system type is widely accepted. However, the quantification of sexual selection has proven problematic. Several measures of sexual selection have been proposed, including the operational sex ratio (OSR), the breeding sex ratio (BSR), and the opportunity for sexual selection (I(mates)). For a wild population of pronghorn (Antilocapra americana), we calculated OSR and BSR. We estimated I(mates) from census data on the spatial and temporal distribution of receptive females in rut and from a multigenerational genetic pedigree. OSR and BSR indicated weak sexual selection on males, but census and pedigree I(mates) suggested stronger sexual selection on males than on females. OSR and BSR correlated with census but not pedigree estimates of I(mates), and census I(mates) did not correlate with pedigree estimates. This suggests that the behavioral mating system, as deduced from the spatial and temporal distribution of females, does not predict the genetic mating system of pronghorn. The differences we observed between estimators were primarily due to female mate sampling and choice and to the sex ratio. For most species, behavioral data are not perfectly accurate and therefore will be an insufficient alternative to using multigenerational pedigrees to quantify sexual selection.     

Secular changes in the height of Polish schoolboys from 1955 to 1988

Secular changes in height have been observed in many regions of Poland using cross-sectional data; however, data from four nationally representative surveys conducted from 1955 to 1988 have only been partially analyzed. Dramatic social and economic transitions during this 33 year period provide a unique opportunity to understand changes in growth within this historic context. We analyzed the changes in height of boys, aged 7–18 years, from surveys conducted in 1955, 1966, 1978 and 1988.Data for height were converted to Z-scores using the LMS method and the 2000 National Center for Health Statistics reference. In each consecutive survey year, boys at all ages were significantly taller than the same aged boys from the previous survey year, with mean height increases of a 2.35 cm, 3.43 cm and 1.47 cm between 1955 and 1966, 1966 and 1978 and 1978 and 1988, respectively. There were significant declines with age in height Z-scores from 7 to 14 years of age, followed by improvements relative to the reference between 14 and 18 years of age. The decline in Z-scores may be partially explained by an effect of delayed maturation. However, historic context also supports that some birth cohorts likely experienced a more adverse environment during early childhood than did other birth cohorts.     

Effects of nematode parasitism on mycophagous drosophilid species in northern Japan

Mycophagous drosophilids and their nematode parasites were studied in an intensive census conducted throughout the active season over four years (2000–2003) in Hokkaido, northern Japan. Using census data, I assessed the prevalence of nematode parasitism through seasons, determined its effects on drosophilid female fertility and tested the “disproportionate parasitism hypothesis” to evaluate its effects on drosophilid community structure. Over the four‐year census, a total of 43 fungal species were found on the census route and 18 177 adult drosophilid flies were collected. The yearly parasitism rate on the total drosophilid community varied from 6.2% in 2000 to 5.1% in 2001 and 3.0% in 2002 and 2003. There was strong seasonal variation in the prevalence of parasitism. In addition, parasitism rates varied among drosophilid species. All parasitized females carried only small numbers of eggs. Thus, nematode parasitism had a strong deleterious effect on the fitness of infected flies. The relative abundance of drosophilid species and parasitism rate were not significantly correlated. Thus, the disproportionate parasitism hypothesis likely does not apply to the mycophagous drosophilid community in Japan.     

Secular rates and correlates for gastroschisis in California (1968-1977)

This study reports on an epidemiological investigation of gastroschisis using birth certificate data from California for the period of 1968-1977. Gastroschisis has been reported to be on the increase in a number of countries. The distribution of the 166 California gastroschisis cases reported during this time period indicated a clear upward secular trend (P less than .001) with the rate per 1,000 increasing from .006 in 1968 to .089 by 1977. This secular trend was observed in every maternal age group and for gravidity level 1. Gastroschisis also occurred more frequently among younger mothers (P less than .001) and low gravidity mothers (P less than .001). Omphalocele, another eventration defect, was also examined but did not display an upward secular trend.     

Epidemiologic transition in an isolated indigenous community in the Valley of Oaxaca, Mexico

The objective of the present study is to analyze age-specific mortality in a rural indigenous community in the throes of a secular increase in size in the Valley of Oaxaca, southern Mexico, over 30 years, 1970-1999. Variation in mortality by age group was analyzed over time for evidence of an epidemiological transition. The seasonal rain pattern in the Valley of Oaxaca (83% from May through September) was evaluated for its relationship with mortality in wet and dry months. Mortality and causes of death changed markedly over the 30-year interval. Infant and preschool mortality, overall mortality, and causes of death changed from the 1970s through the 1990s. Prereproductive deaths (<15 years) predominated in the 1970s and were largely due to gastrointestinal and respiratory diseases, with periodic outbreaks of measles. Deaths of adults 65+ years predominated in the 1990s and were largely due to degenerative diseases usually associated with aging. The marked changes in age and causes of death over the three decades (epidemiologic transition from Stage I to Stage II) occurred concurrently with significant secular increases in body size in children, adolescents, and young adults, highlighting improved health and nutritional conditions in the community which is in early Stage II of the demographic transition. The demographic transition to Stage II is a leading indicator (15-25 years lag) for the onset of the secular trend, while the epidemiologic transition to Stage II is a predictor that the secular increase is in process in the study community.     

Does natural selection favour taller stature among the tallest people on earth?

The Dutch are the tallest people on earth. Over the last 200 years, they have grown 20 cm in height: a rapid rate of increase that points to environmental causes. This secular trend in height is echoed across all Western populations, but came to an end, or at least levelled off, much earlier than in The Netherlands. One possibility, then, is that natural selection acted congruently with these environmentally induced changes to further promote tall stature among the people of the lowlands. Using data from the LifeLines study, which follows a large sample of the population of the north of The Netherlands (n = 94 516), we examined how height was related to measures of reproductive success (as a proxy for fitness). Across three decades (1935–1967), height was consistently related to reproductive output (number of children born and number of surviving children), favouring taller men and average height women. This was despite a later age at first birth for taller individuals. Furthermore, even in this low-mortality population, taller women experienced higher child survival, which contributed positively to their increased reproductive success. Thus, natural selection in addition to good environmental conditions may help explain why the Dutch are so tall.     

Demography and blood genetics of Argentinian Mapuche Indians

The whole Mapuche Indian community of Blancura Centro was covered by a demographic census, with special attention given to variables of genetic interest. Afterwards a sample of it was investigated in relation to 22 genetic systems. The community can be characterized as a young group, with high fertility, but moderate mortality and endogamy. The index of opportunity for selection is relatively low (0.46). The presence of variation at the ABO and Lutheran loci suggests some non-Indian admixture, calculated as 7% in the sample studied. Unusual findings were the absence of L^*NS, low frequency (7%) of L^*MS and high frequency (37%) of L^*Ns. They also showed low frequencies of P^*1 (28%) and DI^*a (3%), but high of HP^*1 (74%). Similarities, but also differences, were noted with previous results obtained in this tribe in Argentina and Chile.     

基于生态经济分区的土壤质量及其变化与农户行为分析

通过1980年土壤普查数据和1999～2000年土壤质量调查和地下水调查数据进行对比和空间计算,看出土壤质量变化在空间上存在较大的空间变异性;在综合自然、社会经济信息,对曲周县进行的生态经济综合分区基础上进行农户调查,对各分区土壤质量状况及其变化以及不同分区之间农户行为差异的分析表明：农户主要通过种植行为选择和经营投人和资源利用等行为对土壤质量和环境产生影响。不同类型农户在种植行为选择和经营投入上有较大差别．     

Sociodemographic differentials in mortality during the 1974-75 famine in a rural area of Bangladesh

This study investigates the socio-demographic differentials in mortality during the 1974-75 famine in a rural area of Bangladesh. It is based on household socioeconomic information collected in the 1974 census and registration data on births, deaths and migrations for the period 1974-79 from the Demographic Surveillance System of the International Centre for Diarrhoeal Disease Research, Bangladesh. Ownership of selected household items was considered in the analysis as an indicator of household socioeconomic status. Mortality was 62% higher during the famine period and 31% higher during the post-famine period compared to the non-famine period. The mortality of both the poor and the rich increased during the famine period, by 117% and 28% respectively compared to the non-famine period. The poor suffered significantly in all age groups except 5-14 years, while the rich suffered only for ages 65 and over. Poor males suffered more than poor females except for ages 65 and over, while rich females suffered more than rich males except for ages under 1 year.     

Detection of deleterious genotypes in multigenerational studies. III. Estimation of selection components in highly selfing populations

New paradigms in genetics have increased the chance of finding genes that appear redundant but in fact may have been preserved due to a small level of positive selection potential acting during each generation. Monitoring changes in genotypic frequencies within and between generations allows the dissection of the fertility, viability and meiotic drive selection components acting on such genes in natural and experimental populations. Here, a formal maximum likelihood procedure is developed to identify and estimate these selection components in highly selfing populations by fitting the time-dependent solutions for genotypic frequencies to observed multigenerational counts. With adult census alone, we can not simultaneously estimate all three selection components considered. In such cases, we instead consider a hierarchy of 11 models with either fewer selection components, complete dominance, or multiplicative meiotic drive with a single parameter. We identify the best-fitting of these models by applying likelihood ratio tests to nested models and Akaike's Information Criterion (AIC) and the Bayesian Information Criterion (BIC) to non-nested models. With seed census, fertility and viability selection are not distinguishable and thus can only be estimated jointly. A combination of joint seed and adult census data allows us to estimate all three selection components simultaneously. Simulated data validate the estimation procedure and provide some practical guidelines for experimental design. An application to Arabidopsis data establishes that viability selection is the major selective force acting on the ACT2 actin gene in laboratory-grown Arabidopsis populations.