海岱地区大汶口文化时期人口死亡年龄的统计分布特征

人口死亡年龄是揭示一个族群健康状况和社会经济条件的重要指标。本文根据海岱地区大汶口文化时期九个墓地人骨遗存的发掘报告,运用定量统计的方法检验了人口死亡年龄分布特征。发现该区大汶口文化时期人口的死亡年龄分布近似服从正态分布。最后探讨了造成人口低死亡年龄的可能原因,并给出了这一概率分布的数学意义以及在史前人口学中的应用前景。     

Maximum likelihood estimate of life expectancy in the prehistoric Jomon: Canine pulp volume reduction suggests a longer life expectancy than previously thought

Recent theoretical progress potentially refutes past claims that paleodemographic estimations are flawed by statistical problems, including age mimicry and sample bias due to differential preservation. The life expectancy at age 15 of the Jomon period prehistoric populace in Japan was initially estimated to have been ～16 years while a more recent analysis suggested 31.5 years. In this study, we provide alternative results based on a new methodology. The material comprises 234 mandibular canines from Jomon period skeletal remains and a reference sample of 363 mandibular canines of recent‐modern Japanese. Dental pulp reduction is used as the age‐indicator, which because of tooth durability is presumed to minimize the effect of differential preservation. Maximum likelihood estimation, which theoretically avoids age mimicry, was applied. Our methods also adjusted for the known pulp volume reduction rate among recent‐modern Japanese to provide a better fit for observations in the Jomon period sample. Without adjustment for the known rate in pulp volume reduction, estimates of Jomon life expectancy at age 15 were dubiously long. However, when the rate was adjusted, the estimate results in a value that falls within the range of modern hunter‐gatherers, with significantly better fit to the observations. The rate‐adjusted result of 32.2 years more likely represents the true life expectancy of the Jomon people at age 15, than the result without adjustment. Considering ～7% rate of antemortem loss of the mandibular canine observed in our Jomon period sample, actual life expectancy at age 15 may have been as high as ～35.3 years.     

Life expectancy of the 20th century Venda: A compilation of skeletal and cemetery data

Little information is available on the 20th century mortality rates of rural black South African groups, such as the Venda. The purpose of this study was to apply abridged life tables in order to estimate life expectancy from both skeletal remains and death registry information of modern South African communities. Comparisons were also made with prehistoric and contemporary groups as a means to better evaluate life expectancy for this time period. The sample consisted of 160 skeletons of known Venda origin and burial registry information for 1364 black South Africans from the Rebecca Street and Mamelodi Cemeteries in Pretoria, South Africa. Standard anthropological techniques were applied to determine sex and estimate age from the skeletal remains. The stationary and non-stationary life table models were used to analyse the data. A high rate of child mortality, low juvenile and adult mortality with a steady increase in mortality after the age of 30 years was observed for both the Venda and the cemetery samples. Throughout the 20th century, life expectancy was shown to increase for black South Africans. However, due to the widespread HIV infection/AIDS of the 21st century, infant and young adult mortality rates continue to rise at such a speed that the decline in mortality seen for South Africans in the last 50 years will most likely to be lost in the next decade due to this disease.     

Trends in stature in the South Australian Aboriginal Murraylands

Millennial and secular changes in body height of prehistoric and recent Aboriginal South Australians are investigated. Skeletal remains of 55 male and 40 female individuals who were excavated at Roonka on the River Murray were dated from 9800 to 100 years BP. Stature was reconstructed by using humerus, femur, and tibia ratios to stature derived from Abbie's (1975) data on living Aborigines and the Trotter-Gleser method for blacks. The respective averages were 1,652 mm and 1,665 mm for males and 1,527 mm and 1,549 mm for females. In 1996/1997, statures of 27 adult males and 21 adult females were measured in Aboriginal centers of Gerard and Raukkan (Point McLeay) on the Lower River Murray. These people, as far as it can be ascertained, are the descendants of the people from Roonka. Their statures were adjusted for the stature loss with age, so that the data represent young individuals (≤30 years of age). The average male stature was 1,712 mm, and the average female stature was 1,567 mm. Data collected by Wood Jones and Campbell in 1924 for Aboriginal South Australians show that young adult male stature was 1,668 mm (n = 6), and female stature was 1,552 mm (n = 4). Slopes of regressions of individual statures on radiocarbon dates and on dates of birth are not significantly different from zero. The same is true for regressions of individual long bone lengths on radiocarbon dates. It can be concluded that there was little change in stature of Aboriginal South Australians from prehistoric to recent times. Regressions of individual age-corrected heights on birth dates (1860–1980) of Aboriginal men and women measured in 1924 and in 1996 further indicate no significant increase in height in either sex. Am J Phys Anthropol 106:505–514, 1998. © 1998 Wiley-Liss, Inc.     

Calculation of longevity and life expectancy in captive elephants

The concepts of longevity (longest lived) and life expectancy (typical age at death) are common demographic parameters that provide insight into a population. Defined as the longest lived individual, longevity is easily calculated but is not representative, as only one individual will live to this extreme. Longevity records for North American Asian elephants (Elephas maximus) and African elephants (Loxodonta africana) have not yet been set, as the oldest individuals (77 and 53 years, respectively) are still alive. One Asian elephant lived to 86 years in the Taipei Zoo. This is comparable to the maximum (though not typical) longevity estimated in wild populations. Calculation of life expectancy, however, must use statistics that are appropriate for the data available, the distribution of the data, and the species' biology. Using a simple arithmetic mean to describe the non‐normally distributed age at death for elephant populations underestimates life expectancy. Use of life‐table analysis to estimate median survivorship or survival analysis to estimate average survivorship are more appropriate for the species' biology and the data available, and provide more accurate estimates. Using a life‐table, the median life expectancy for female Asian elephants (Lx=0.50) is 35.9 years in North America and 41.9 years in Europe. Survival analysis estimates of average life expectancy for Asian elephants are 47.6 years in Europe and 44.8 years in North America. Survival analysis estimates for African elephants are less robust due to less data. Currently the African elephant average life expectancy estimate in North America is 33.0 years, but this is likely to increase with more data, as it has over the past 10 years. Zoo Biol 23:365–373, 2004. © 2004 Wiley‐Liss, Inc.     

Estimated life expectancy and risk of death from cancer by quartiles in the older Japanese population: 2010 vital statistics

Data on life expectancies and risk of death from cancer are essential information to have when making informed decisions about cancer screening and treatment options, but has never been presented in a way that is readily available to use for physicians in Japan. We provided estimates of life expectancies and predicted risk of death from seven most common types of cancer (lung, gastric, liver, colon, prostate, breast, and cervical) by quartiles for the older Japanese population above 50 years old, using 2010 life tables and cancer mortality statistics data. We found that there was a large difference in life expectancy between older persons in the upper and lower quartiles. Risk of death from breast cancer was low. By using this data, physicians can more accurately obtain life expectancy estimates by assessing which quartile the patient is most likely to fall under, and help patients make better informed decisions.     

Life Expectancy and Death by Diseases of the Circulatory System in Patients with Bipolar Disorder or Schizophrenia in the Nordic Countries

Objective

Excess mortality from diseases and medical conditions (natural death) in persons with psychiatric disorders has been extensively reported. Even in the Nordic countries with well-developed welfare systems, register based studies find evidence of an excess mortality. In recent years, cardiac mortality and death by diseases of the circulatory system has seen a decline in all the Nordic countries, but a recent paper indicates that women and men in Denmark, Finland, and Sweden, who had been hospitalised for a psychotic disorder, had a two to three-fold increased risk of dying from a cardiovascular disease. The aim of this study was to compare the mortality by diseases of the circulatory system among patients with bipolar disorder or schizophrenia in the three Nordic countries Denmark, Sweden, and Finland. Furthermore, the aim was to examine and compare life expectancy among these patients. Cause specific Standardized Mortality Rates (SMRs) were calculated for each specific subgroup of mortality. Life expectancy was calculated using Wiesler’s method.

Results

The SMR for bipolar disorder for diseases of the circulatory system was approximately 2 in all countries and both sexes. SMR was slightly higher for people with schizophrenia for both genders and in all countries, except for men in Denmark. Overall life expectancy was much lower among persons with bipolar disorder or schizophrenia, with life expectancy being from 11 to 20 years shorter.

Conclusion

Our data show that persons in the Nordic countries with schizophrenia or bipolar disorder have a substantially reduced life expectancy. An evaluation of the reasons for these increased mortality rates should be prioritized when planning healthcare in the coming years.     

An extraordinary life span estimate for the clown anemonefish Amphiprion percula

A population of the clown anemonefish Amphiprion percula was studied for 1 year, in Madang Lagoon, Papua New Guinea. From this study, data on mortality events and social structure were used to construct a stage-structured matrix model and estimate the average age at death (life expectancy) of various classes of individuals. Based on this model, it is estimated that the life expectancy of female A. percula , the oldest individuals in the population, is 30 years. This estimate is two times greater than the longevity estimated for any other coral reef damselfish and six times greater than the longevity expected for a fish of that size. The result complements the growing body of evidence, from widespread taxa, that organisms subject to low levels of extrinsic mortality show retarded senescence and increased longevity. It is suggested that fishes would be an excellent group for a broad scale comparative test of the predictions of the evolutionary theory of ageing.     

Moribund Ants Do Not Call for Help

When an antlion captures a foraging ant, the victim’s nestmates may display rescue behaviour. This study tested the hypothesis that the expression of rescue behaviour depends on the life expectancy of the captured ant. This hypothesis predicts that the expression of rescue behaviour will be less frequent when the captured ant has a lower life expectancy than when it has a higher life expectancy because such a response would be adaptive at the colony level. Indeed, significant differences were found in the frequency of rescue behaviours in response to antlion victims with differing life expectancies. In agreement with prediction, victims with lower life expectancies were rescued less frequently, and those rescues had a longer latency and shorter duration. There was also a qualitative difference in the behaviour of rescuers to victims from the low and high life expectancy groups. Several explanations for these findings are proposed.     

Reproduction now or later: optimal host-handling strategies in the whitefly parasitoid Encarsia formosa

We developed a dynamic state variable model for studying optimal host‐handling strategies in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We assumed that (a) the function of host feeding is to gain nutrients that can be matured into eggs, (b) oögenesis is continuous and egg load dependent, (c) parasitoid survival is exponentially distributed and (d) parasitoids encounter hosts randomly, are autogenous and have unlimited access to non‐host food sources to obtain energy for maintenance and activity. The most important prediction of the model is that host feeding is maladaptive under field conditions of low host density (0.015 cm^?2) and short parasitoid life expectancy (maximum reproductive period of 7 d). Nutrients from the immature stage that can be matured into eggs are sufficient to prevent egg limitation. Both host density and parasitoid life expectancy have a positive effect on the optimal host‐feeding ratio. Parasitoids that make random decisions gain on average only 35% (0.015 hosts cm^?2) to 60% (1.5 hosts cm^?2) of the lifetime reproductive success of parasitoids that make optimal decisions, independent of their life expectancy. Parameters that have a large impact on lifetime reproductive success and therefore drive natural selection are parasitoid life expectancy and the survival probability of deposited eggs (independent of host density), the number of host encounters per day (when host density is low) and the egg maturation rate and number of host types (when host density is high). Explaining the evolution of host‐feeding behaviour under field conditions requires field data showing that life expectancy in the field is not as short as we assumed, or may require incorporation of variation in host density. Incorporating variation in walking speed, parasitised host types or egg resorption is not expected to provide an explanation for the evolution of host‐feeding behaviour under field conditions.     

A note on the reduction of a risk of death

Abstract

Methods for assessing the gain of life expectancy by reducing the risks of death are examined. Depending on the method used, overestimation and underestimation of life expectancy may occur. Although the gain in life expectancy is not a linear function of the per cent reduction in mortality, a linear approximation may be used when the mortality rate is low. When the mortality rate is high, linear approximations tend to overestimate the years gained. A method using the parameter H⁽ⁱ⁾ developed by Keyfitz (1977) is adequate for low mortality rates such as with neoplasms. However, when mortality rates are high, as they are for cardiovascular‐renal diseases (CVD), Keyfitz's method tends to underestimate the gain in life expectancy. For CVD, Keyfitz's estimation is adequate below the 20 per cent reduction range. The magnitude of overestimation and underestimation are numerically evaluated based on the 1964 United States male mortality statistics.     

Stable nitrogen and carbon isotope ratios in bone collagen as indices of prehistoric dietary dependence on marine and terrestrial resources in southern California

The ratios of 15N to 14N and 13C to 12C tend to be higher in marine than in terrestrial organisms. The concentrations of these isotopes in human bone collagen consequently can be used to make inferences about the contribution of marine and terrestrial resources to prehistoric diets. The utility of studying 15N/14N and 13C/12C ratios in conjunction with each other is illustrated by our analysis of 40 human burials from archaeological sites in the Santa Barbara Channel area of southern California. The mean delta 13C and delta 15N values (in per mil) of collagen from these skeletons decrease progressively from the Channel Islands (delta 13C = -14.0, delta 15N = +16.3) to the mainland coast (delta 13C = -14.5, delta 15N = +14.9) to the interior (delta 13C = -17.2, delta 15N = +10.9). These data suggest that Indians living on the Channel Islands during the late prehistoric period were heavily dependent on marine resources. The inhabitants of the mainland interior, in contrast, had a diet composed largely of terrestrial foods. From their isotope ratios, it appears that the Indians who lived on the mainland coast consumed a mixed diet containing substantial quantities of both marine and terrestrial resources. Differences in 15N/14N and 13C/12C ratios of individuals from mainland sites dating from the early and late prehistoric periods show that the marine component of the diet increased substantially through time. These isotopic data are consistent with pathological, faunal, and artifactual evidence of increased marine resource exploitation during the late prehistoric period.     

Sex and Life Expectancy

BackgroundA sexual dimorphism in human life expectancy has existed in almost every country for as long as records have been kept. Although human life expectancy has increased each year, females still live longer, on average, than males. Undoubtedly, the reasons for the sex gap in life expectancy are multifaceted, and it has been discussed from both sociological and biological perspectives. However, even if biological factors make up only a small percentage of the determinants of the sex difference in this phenomenon, parity in average life expectancy should not be anticipated.ObjectiveThe aim of this review is to highlight biological mechanisms that may underlie the sexual dimorphism in life expectancy.MethodsUsing PubMed, ISI Web of Knowledge, and Google Scholar, as well as cited and citing reference histories of articles through August 2012, English-language articles were identified, read, and synthesized into categories that could account for biological sex differences in human life expectancy.ResultsThe examination of biological mechanisms accounting for the female-based advantage in human life expectancy has been an active area of inquiry; however, it is still difficult to prove the relative importance of any 1 factor. Nonetheless, biological differences between the sexes do exist and include differences in genetic and physiological factors such as progressive skewing of X chromosome inactivation, telomere attrition, mitochondrial inheritance, hormonal and cellular responses to stress, immune function, and metabolic substrate handling among others. These factors may account for at least a part of the female advantage in human life expectancy.ConclusionsDespite noted gaps in sex equality, higher body fat percentages and lower physical activity levels globally at all ages, a sex-based gap in life expectancy exists in nearly every country for which data exist. There are several biological mechanisms that may contribute to explaining why females live longer than men on average, but the complexity of the human life experience makes research examining the contribution of any single factor for the female advantage difficult. However, this information may still prove important to the development of strategies for healthy aging in both sexes.     

对采用平均叶龄估算叶年净初级生产量的修正

 根据森林和林木各器官生物量随时间的变化,林冠叶片(叶群体)生长和死亡规律及数学生态学的原理,得出了叶的生物量、年净生产量和平均叶龄之间的关系。一般表达式为P=│lnlx│·B/x(式中Pn为叶年净生产量,lx为特定叶龄的存留率,B为叶生物量,x为平均叶龄)。当林冠叶片达到平衡时,Pn=0.693·B／x;存留率为36.8%时,成为目前用平均叶龄计算叶年净初级生产量的形式。本文证明了后一种特殊形式之所以被人们广泛采用是因为混淆了平均叶龄与叶量周转时间这两个概念;这种方法估算的结果比正常值约高30%。 还用实例讨论了用0—1龄级平均叶龄估算叶净生产量所不可避免的偏大原因,用本文提出的公式对某些叶净生产量的计算数值进行了修正;结果表明,与实际情况比较吻合。     

Biosocial covariates of adult male body mass index in Central India

Body mass index (BMI) is the 'measuring rod' of nutritional status. This study investigates the type and extent of correlation between adult male BMI and socioeconomic, cultural and bio-demographical variables using data from 11,496 individuals from 38 districts of Central India. For each individual, stature, body weight and sitting height data were collected, their Cormic index and BMI computed, and averages for each district calculated. Mean BMI was found to be lowest for the population of Tikamgarh (17.90+/-1.91 kg m(-2)) and highest for that of Durg district (19.33+/-2.16 kg m(-2)), whereas the mean BMI for the total population of Central India was 18.67+/-2.18 kg m(-2), which is lower than that of well-to-do individuals in India as a whole. The F ratio indicates that there is inter-district variation in anthropometric characteristics of populations. District-wise biosocial indicators were obtained, namely population density per square kilometre, percentage urban population, percentage of population that is of scheduled caste/tribe, sex ratio, average rural population per PHC/CHC (primary or community health centre), literacy rate, life expectancy, total fertility rate, infant mortality rate, gender development index and human development index. Most of these variables were found to be significantly correlated with each other, but BMI was only significantly correlated with three of them, viz. gender development index (R2=0.211), life expectancy (R2=0.130) and infant mortality rate (R2=0.128). Gender development index and life expectancy were positively correlated with BMI, whereas infant mortality rate was negatively correlated. It is concluded that if BMI increases then life expectancy will also increase. Thus better nutritional status may be a helpful tool for reducing infant mortality rate, which is an indicator of socioeconomic status, health condition, health care and ultimately overall development of a region or population.     

Reconstruction of prehistoric Lake Cahuilla in the Salton Sea Basin using GIS and GPS

During prehistoric times, the Colorado River occasionally meandered into and filled the Salton Sea Basin, creating several huge inland lakes, variously called Lake LeConte and Lake Cahuilla. Previous researchers have identified high stands of these ancient lakes using standard survey methods. The objective of this investigation was to further delineate the prehistoric shorelines using satellite imagery, global positioning system (GPS) and geographic information system (GIS) technologies. Using one-meter digital orthophotographs, points were selected in the laboratory and were located in the field using a GPS. Point data were integrated with a digital elevation model (DEM) and elevation contours were plotted on Landsat-TM images, generating a range of prehistoric shorelines. Contours were then correlated with archaeological site data, geomorphic features, and other factors to reconstruct Early American settlement patterns for Lake Cahuilla. The combined GIS coverages of ancient Lake Cahuilla and cultural resources may be used together as a model for cultural resource constraints, identifying areas of high cultural resource sensitivity for evaluation of potential impacts as a result of implementation of Salton Sea restoration project alternatives.     

An ancient bottleneck in the Lost Pines of central Texas

The retreating edge hypothesis for species responding to climate change predicts severe bottlenecks and eventual extinction. The disjunct Lost Pines population at the westernmost edge of the widespread Pinus taeda range is well suited for testing this prediction. The occurrence of one or more genetic bottlenecks in the Lost Pines population was tested using 34 nuclear microsatellite markers and a control sample from the larger, more continuous east Texas P. taeda forests. The Lost Pines population has undergone drastic contractions in effective population size between 3000 and 30 000 years bp. These results were supported by: (i) detection of transient heterozygosity excess, (ii) a mode-shift indicator of allele frequencies, and (iii) a ratio of allele number to allele size range. No bottleneck was detected for the east Texas control using any of the three methods. The distribution of allele frequencies was skewed for the Lost Pines population compared to the control, indicating a loss of rare alleles. However, allelic diversity was similar between the Lost Pines population and its east Texas control; the mean allele number per locus was 5.29 and 5.38, respectively. It is proposed that the Lost Pines population was the western refugium for P. taeda during Pleistocene glaciation and that East Texas P. taeda forests descended from the bottlenecked Lost Pines population.     

Examining the Relationship between Life Expectancy,Reproduction, and Educational Attainment

Life history theory aims to explain the relationship between life events, recognizing that the fertility and growth schedules of organisms are dependent on environmental conditions and an organism’s ability to extract resources from its environment. Using models from life history theory, we predict life expectancy to be positively correlated with educational investments and negatively correlated with adolescent reproduction and total fertility rates. Analyses of UN data from 193 countries support these predictions and demonstrate that, although variation is evident across world regions, strong interactions exist among life expectancy, reproductive investments, and educational attainment, and these relationships occur independently of economic pressures and disease burdens. The interactions are strongest, however, in countries with a life expectancy of ≥60 years as these countries tend to have stable economies and a limited HIV/AIDS burden. These findings suggest that policies aimed at influencing education and reproductive decisions should consider environmental characteristics that drive people’s expectations about their longevity.     

On generating birth rates from skeletal populations

Sattenspiel and Harpending (1983, American Antiquity 48(3): 489-498) have stated that the life expectancy at birth (e0(0] which paleodemographers calculate from skeletal population data is actually the mean age at death (ad) of the population. Yet, only when a population is neither growing or declining (i.e., is stationary) are these two statistics equivalent. They further assert, that the mean age at the death (ad) is more accurately interpreted as a measure of the fertility of the population. While we support their statement that since paleodemographic calculations use skeletal evidence of death, these do not a priori produce life expectancy values, we disagree that the inverse of the birth rate is a substitute for the average age at death (ad). The following pages demonstrate that: 1) An exact expression for the relationship between ad and 1/b can be derived using standard stable population theory, wherein ad = 1/b is shown to be a special case. 2) There are only two cases when ad = 1/b is an identity. 3) Whereas empirically ad and 1/b appear to correspond closely, this is an artifact of heavy mortality at early ages, which is a characteristic of the populations being considered. 4) Without insights into the behavioral dynamics of the situation any assessment of the demographics of the population is questionable.     

Estimating Attributable Life Expectancy Under the Proportional Mean Residual Life Model

In population-based health research, the so-called population attributable fraction is an important quantity that calculates the percentage of excess risk of morbidity and mortality associated with modifiable risk factors for a given population. While the concept of “risk” is usually measured by event probabilities, in practice it may be of a more direct interest to know the excess life expectancy associated with the modifiable risk factors instead, particularly when mortality is of the ultimate concern. In this paper, we thus propose to study a novel quantity, termed “attributable life expectancy,” to measure the population attributable fraction of life expectancy. We further develop a model-based approach for the attributable life expectancy under the Oakes–Dasu proportional mean residual life model, and establish its asymptotic properties for inferences. Numerical studies that include Monte-Carlo simulations and an actual analysis of the mortality associated with smoking cessation in an Asia Cohort Consortium are conducted to evaluate the performance of our proposed method.