Estimating fertility using adults: A method for under-enumerated pre-adult skeletal samples

Objectives

Infant underrepresentation poses a great risk to accurate palaeodemographic findings when analyzing skeletal samples. Empirically derived palaeodemographic methods all require unbiased or minimally biased pre-adult representation for estimating demographic characteristics, including fertility. Currently, there are no reliable methods for estimating palaeodemographic parameters when pre-adults are underrepresented in skeletal samples, consequently such samples are often excluded from palaeodemographic analyses. The aim of this article is to develop a method for estimating total fertility rate (TFR) using reproductive aged adults, specifically for samples with suspected pre-adult under-enumeration.

Methodology

United Nations mortality data and TFR from the World Population Prospects was utilized. The correlation between known fertility and the proportion of individuals in key reproductive years (15–49 years) to total adult sample (15+ years) was assessed as an indirect means to estimate fertility.

Results

It was determined that the proportion of reproductive aged adults is a reasonable proxy for fertility. A significant positive correlation was observed between the TFR and those who died aged 15–49 years of age as a proportion of those who died ≥15 years (D15-49/D15+). SE of the estimate revealed reasonable predictive accuracy. When applied to two modern non-agricultural populations, the method showed some variability in accuracy but good potential for an improved outcome over existing methods when pre-adults are underrepresented.

Conclusion

This research has provided a new method for estimating fertility in archeological skeletal samples with pre-adult under-enumeration. In combination with a contextually focused approach, this provides a significant step toward further use of biased samples in palaeodemography.

     

Assessing the association of skeletal indicators of stress with mean age-at-death in sub-adults

Objectives

The present study investigated the association of skeletal indicator of stress presence with mean age-at-death as a means of understanding whether commonly studied indicators are indeed indicative of increased frailty.

Materials and Methods

Using a medieval Gaelic population from Ballyhanna (Co. Donegal), the present study assessed the association between skeletal indicators of stress and mean age-at-death using the Kaplan–Meier survival function with log rank test to determine whether these indicators were associated with younger age-at-death, and therefore increased frailty, in sub-adults only (0 to 18 years, N = 139) and through comparison to an all-ages cohort (N = 318).

Results

Only linear enamel hypoplasia was found to be associated with significantly decreased survivorship across the all-ages cohort but, conversely, was associated with increased survivorship when analysis was restricted to sub-adults. All other indicators assessed were associated with increased age-at-death for both all-age cohorts and sub-adult cohorts (cribra orbitalia), increased age-at-death when assessing all ages only (porotic hyperostosis and healed periosteal lesions); or were sufficiently rare in adults to prevent comparative analysis (stunting and micronutrient deficiency). Increased survivorship in individuals with higher numbers of co-morbid skeletal indicators was observed for both sub-adults alone and all age cohort.

Discussion

These findings suggest that these commonly recorded skeletal indicators may be more accurately viewed simply as records of stressor exposure and subsequent survival only, rather than providing evidence that these sub-adults are frailer than their similarly aged-at-death peers. Thus, the demographic and sociocultural context is essential to the interpretation of observed skeletal indicators of stress.

     

The past,present and future of skeletal analysis in palaeodemography

The study of past population dynamics is imperative to our understanding of demographic processes in the context of biology, evolution, environment and sociocultural factors. Retrospective consideration of a population''s capacity to resist and adapt to change aims to contribute insights into our past, a point of comparison to the present and predictions for the future. If these aims are to be achieved, the accuracy and precision of palaeodemographic methods are of paramount importance. This article considers the emergence of skeletally based palaeodemographic methods, specifically life tables and demographic proxies, and early controversies and issues. It details the process of methodological development and refinement, and success in addressing many of the historical limitations. The contribution and potential of skeletally based methods are discussed and comparisons and contrasts made with alternative palaeodemographic approaches, and avenues for future research are proposed. Ultimately, it is concluded that skeletal analysis provides unique opportunities to investigate population dynamics with spatial specificity, examine individuals and groups within a population, and integrate demographic and pathological information to evaluate population health in the past.This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography''.     

The short die young: the interrelationship between stature and longevity-evidence from skeletal remains

It has long been observed that tall people display longer life spans. The current data were employed to verify this association within the bioarchaeological context. To this end, stature and its association with age-at-death were analyzed in a pooled sample of 2,923 skeletons. Height was estimated from proxy indicators based on the maximum length of the humerus, radius, femur, and tibia. Stature estimation followed the procedure outlined by Pearson ([1899] Philos. Trans. R. Soc. Lond. [A] 192:169-244), incorporating minor modifications by R?sing ([ 1988] Handbuch der vergleichenden Biologie des Menschen; Stuttgart: Gustave Fischer, p 586-600). Individual age estimates were classified into three mutually exclusive age groups: 20-39 years (591 males, 667 females), 40-59 years (876 males, 499 females), and 60+ years (171 males, 119 females). The results document that both sexes display a statistically significant inverse relationship between adult height and age-at-death (males, P < 0.01; females, P < 0.05). Taking an epidemiological approach, the risk model implies that the estimated odds of survival beyond age 40 improve by approximately 16% for 1 SD in bone length. However, not all bones may be equally adept at displaying the association. The radius failed to support the positive association between stature and longevity, which may be indicative of a relatively greater contribution of environmental factor to radius length. Overall, the relationship between body height and longevity is not causal but coincidental: mitigated by diverse environmental factors such as nutrition, socioeconomic stressors, and disease load.     

The Neolithic Demographic Transition in the Central Balkans: population dynamics reconstruction based on new radiocarbon evidence

In this paper, we test the hypothesis of the Neolithic Demographic Transition in the Central Balkan Early Neolithic (6250–5300 BC) by applying the method of summed calibrated probability distributions to the set of more than 200 new radiocarbon dates from Serbia. The results suggest that there was an increase in population size after the first farmers arrived to the study area around 6250 BC. This increase lasted for approximately 250 years and was followed by a decrease in the population size proxy after 6000 BC, reaching its minimum around 5800 BC. This was followed by another episode of growth until 5600 BC when population size proxy rapidly declined, reaching the minimum again around 5500 BC. The reconstructed intrinsic growth rate value indicates that the first episode of growth might have been fuelled both by high fertility and migrations, potentially related to the effects of the 8.2 ky event. The second episode of population growth after 5800 BC was probably owing to the high fertility alone. It remains unclear what caused the episodes of population decrease.This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography''.     

Calcaneus secundarius: description and frequency in six skeletal samples

The calcaneus secundarius (CS) is a small accessory ossicle of the anterior calcaneal facet. A sample of 1,367 calcanei including early 20th century U.S. blacks and whites, XIIth Dynasty Egyptians, Islamic Period Bahrainis, and protohistoric American Indians from two states were examined to determine the frequency of this nonmetric trait. Statistical testing of the correlation of the trait with sex could only be performed on the blacks and whites, a documented cadaver collection. Tests of chi 2 indicated that, although sex differences were insignificant, significant group (not necessarily racial or geographical) differences existed at the .05 level. There was no correlation of side dominance in the overall sample, although significant population differences existed. The trait frequencies of the black and white samples were more similar to one another than to the nonindustrial groups who, in turn, were more similar to each other than to the Terry sample. The findings suggest that a CS is of genetic or congenital origin resulting in a secondary center of ossification in the anterior calcaneal facet.     

抗体几何平均滴度计算中如何处理抗体阴性者？

不同作者在计算抗体几何平均滴度（ＧＭＴ）时，对抗体阴性者的处理方法不完全一致，共有三种：①将抗体阴性者的抗体滴度作为零纳入抗体ＧＭＴ计算；②将抗体阴性者不纳入计算；③用阳性界值的１／２作为阴性者的抗体滴度纳入计算。统计分析国内１１种医学杂志９２篇文献发现，科研机构和医学院校多用第三种方法（５７．１４％），省级和地市县级单位多用第一种方法（４４．８７％）。作者比较分析了三种方法的计算结果及优劣，认为第一种方法较适宜。     

Testing the value of skeletal samples in demographic research: a comparison with vital registration samples

Critics of paleodemography have suggested that the science is so fraught with error that its demise must be close at hand. Among the problems suggested as unsolvable are representativeness of skeletal samples and inaccuray of skeletal aging techniques. A historical skeletal sample with supportive vital registration might afford the opportunity to test the validity of such criticism or at least to examine the extent of the above problems. In 1984, a skeletal sample of 296 individuals was excavated from a 19th century American poorhouse cemetery. Age at death was determined by macroscopic multivariate examination. Mortality records of 247 individuals who died during four years of the poorhouse's operation provide data for demographic comparisons with the skeletal sample. A comparison of life tables generated from each sample demostrates that there are no significant differences in the age at death structure, life expectancy (at birth: 30.7 in the mortality records and 32.6 from the skeletal sample), or survivorship between the two samples. Skeletal aging techniques can, therefore, provide a demographic picture that is similar in accuracy to that presented by vital registration records.     

The FQPA 10X Safety Factor: How Much is Science? How Much is Sociology?

On August 3, 1996, the Food Quality Protection Act of 1996 (FQPA) was signed into law. The FQPA instructed the U.S. Environmental Protection Agency, in making its “reasonable certainty of no harm” finding, that in “the case of threshold effects,…an additional tenfold margin of safety…shall be applied for infants and children to take into account potential pre- and postnatal toxicity and completeness of data with respect to exposure and toxicity to infants and children.” The law further states that “the Administrator may use a different margin of safety……only if, on the basis of reliable data, such margin will be safe for infants and children.” This paper describes how the Office of Pesticide Programs of the U.S. Environmental Protection Agency proposes to implement this legislative mandate in its 1999 draft.     

The settling characteristics and mean settling velocity of granular sludge in upflow anaerobic sludge blanket (UASB)-like reactors

Mean settling velocity of granular sludge in full-scale UASB (upflow anaerobic sludge blanket) and EGSB (expanded granular sludge bed) reactors was evaluated by settling column tests, and a settling velocity model based on the experimental results and available literature data was developed. It is concluded that the settling velocity should be calculated by the Allen formula, because the settling process of the granules is in the category of intermediate flow regime rather than in the laminar flow one. The comparison between calculated and measured values of the settling velocity shows an excellent agreement, with an average relative error of 4.04%. A simple but reliable mathematical method to determine the settling velocity is therefore proposed.     

The legacy of cultural landscapes in the Brazilian Amazon: implications for biodiversity

For centuries Amazonia has held the Western scientific and popular imagination as a primordial forest, only minimally impacted by small, simple and dispersed groups that inhabit the region. Studies in historical ecology refute this view. Rather than pristine tropical forest, some areas are better viewed as constructed or 'domesticated' landscapes, dramatically altered by indigenous groups in the past. This paper reviews recent archaeological research in several areas along the Amazon River with evidence of large pre-European (ca 400-500 calendar years before the present) occupations and large-scale transformations of forest and wetland environments. Research from the southern margins of closed tropical forest, in the headwaters of the Xingu River, are highlighted as an example of constructed nature in the Amazon. In all cases, human influences dramatically altered the distribution, frequency and configurations of biological communities and ecological settings. Findings of historical change and cultural variability, including diverse small to medium-sized complex societies, have clear implications for questions of conservation and sustainability and, specifically, what constitutes 'hotspots' of bio-historical diversity in the Amazon region.     

The ascorbic acid transporter SVCT2 is expressed in slow-twitch skeletal muscle fibres

Ascorbic acid, the reduced form of vitamin C, functions as a potent antioxidant as well as in cell differentiation. Ascorbate is taken up by mammalian cells through the specific sodium/ascorbate co-transporters SVCT1 and SVCT2. Although skeletal muscle contains about 50% of the whole-body vitamin C, the expression of SVCT transporters has not been clearly addressed in this tissue. In this work, we analysed the expression pattern of SVCT2 during embryonic myogenesis using the chick as model system. We cloned the chick orthologue of SVCT2 (cSVCT2) that shares 93% identity with the mouse transporter. cSVCT2 mRNA and protein are expressed during chick embryonic muscle development. Immunohistochemical analyses showed that SVCT2 is preferentially expressed by type I slow-twitch muscle fibres throughout chick myogenesis as well as in post-natal skeletal muscles of several species, including human. Our results suggest that SVCT2-mediated uptake of ascorbate is relevant to the oxidative nature of type I muscle fibres. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. M. Low and D. Sandoval have contributed equally.     

Tooth crown size differences between age groups: A possible new indicator of stress in skeletal samples

Juveniles and adults from a prehistoric Amerindian skeletal series from Tennessee are compared for differences in the means and variances of the buccolingual dimensions of their permanent teeth. While there are no significant differences in variance, it is found that juveniles exhibit significantly smaller mandibular canines, first premolars, and first molars. The results are similar to those of a previous examination of an Amerindian skeletal collection from South Dakota. There is evidence to suggest that teeth may fail to develop to their maximum genetic size potential when there is interference from exogenous chronic stressors such as malnutrition or disease. Archeological and biological evidence demonstrates that both the Tennessee and South Dakota series represent groups that suffered considerably from environmental stressors. It is suggested that those persons who suffered most were more likely to die prematurely, thus explaining why juvenile skeletons tend to have smaller teeth. The conclusion is that the examination of age variation in crown size can be a useful supplement to other osteological indicators of stress in skeletal collections. The factor of sex ratio and the implications of the results for other kinds of dental metric studies are discussed.     

Brief communication: diachronic investigation of linear enamel hypoplasia in prehistoric skeletal samples from Trentino,Italy

Linear enamel hypoplasia was scored on Neolithic, Copper Age, and Early Bronze Age samples from the Trentino region, Italy, in order to compare the extent of growth disruption in different biocultural subsistence systems (foragers with little agriculture, to agriculturists and agropastoralists). The Early Bronze Age sample shows a higher frequency of enamel defects and an earlier chronological onset than the early Neolithic sample. The higher frequency of defects in the Bronze Age sample could be linked to less diversified nutrition and, because of increased sedentism, a higher risk of disease.     

The 60S ribosomal subunit is altered in the skeletal muscle of dystrophic hamsters

Polysomes from the skeletal muscle of normal and dystrophic hamsters were dissociated into ribosomal subunits by treatment with puromycin and the subunits from both strains were reassociated in all possible combinations. When their protein synthesis activity was assayed in a poly(U)-directed cell-free system at a low magnesium concentration, the reassociated ribosomes from dystrophic hamsters were less active than the ribosomes from control animals. The ribosomal defect is a property of the 60S subunit and is due to a ribosomal component rather than to abnormal binding of a non-ribosomal protein.     

The legacy of transnational lives: Beyond the first generation of Lebanese in Senegal

Definitions of transnationalism are modelled after first generation migrant communities in the west. Through presenting ethnographic detail on the Lebanese community in Senegal, this article applies the concept of transnationalism to the case of a historic South-South migrant community. Second and later generation ethnic groups maintain transnational ties through notions of self-identity and definitions by others, the importance given to the homeland, and political and religious ideologies. Race, geographic location, and changes in the structure of labour markets are factors that encourage continued ties with the country of origin. Furthermore, transnationalism cannot be limited only to sending and receiving countries. Colonial and former colonial powers can determine the destination of migrants, establish economic hierarchies, and offer a tertiary citizenship to transnational migrants in addition to the dual citizenship of country of origin and destination.