From the Ground Up: A Multidisciplinary Approach to Past Fertility and Population Narratives.

Population dynamics form a crucial component of human narratives in the past. Population responses and adaptations not only tell us about the human past but also offer insights into the present and future. Though an area of substantial interest, it is also one of often limited evidence. As such, traditional techniques from demography and anthropology must be adapted considerably to accommodate the available archaeological and ethnohistoric data and an appropriate inferential framework must be applied. In this article, I propose a ground-up, multidisciplinary approach to the study of past population dynamics. Specifically, I develop an empirically informed path diagram based on modern fertility interactions and sources of past environmental, sociocultural, and biological evidence to guide high-resolution case studies. The proposed approach is dynamic and can evolve in response to data inputs as case studies are undertaken. In application, this approach will create new knowledge of past population processes which can greatly enhance our presently limited knowledge of high-frequency, small-scale demographic fluctuations, as well as contribute to our broader understanding of significant population disturbances and change throughout human history.

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.

Paleoepidemiology of cribra orbitalia: Insights from early seventh millennium BP Con Co Ngua, Vietnam.

OBJECTIVES: We test the hypothesis that the condition(s) leading to the development of cribra orbitalia at Con Co Ngua, an early seventh millennium sedentary foraging community in Vietnam, effectively reduced the resilience of the population to subsequent health/disease impacts. An assessment of both the implications and potential etiology of cribra orbitalia in this specific population is carried out. METHODS: The effective sample included 141 adults aged ≥15 years (53 females, 71 males, and 17 unknown sex) and 15 pre-adults aged ≤14 years. Cribra orbitalia was identified by way of cortical bone porosity of the orbital roof initiated within the diplöic space, rather than initiated subperiosteally. The approach is also robust to the misidentification of various pseudo-lesions. Resultant data was analyzed using Kaplan-Meier survival analysis. RESULTS: Median survival is higher in adults aged ≥15 years without cribra orbitalia than those with this lesion. For the pre-adult cohort, the opposite pattern is seen where median survival is higher in those with cribra orbitalia than those without. CONCLUSION: Adults displayed increased frailty and pre-adults increased resilience with respect to cribra orbitalia. The differential diagnosis for a survival analysis of adults and pre-adults with and without cribra orbitalia included iron deficiency anemia and B12/folate deficiency, parasitism (including hydatid disease and malaria) in addition to thalassemia. The most parsimonious explanation for observed results is for both thalassemia and malaria being the chief etiological agents, while appreciating these conditions interact with, and can cause, other forms such as hematinic deficiency anemias.

A meta-analytic review of the frequency and patterning of laryngohyoid and cervical fractures in cases of suicide by hanging.

The frequency and distribution of fractures are commonly utilized to assist in interpreting the manner of death. In cases of alleged suicide by hanging, however, the evidence base for the frequency and patterning of laryngohyoid and cervical vertebrae fractures resulting from such blunt force traumatic events is limited and so fractures cannot be reliably used to assist in interpreting the manner. Using meta-analytic techniques, this study aimed to estimate frequency and distribution of fractures in the context of relevant intrinsic and extrinsic variables. A systematic review of the literature identified 20 studies with relevant data (8523 cases of suicide by hanging). Meta-analyses identified the frequency and distribution of fractures present and how fracture frequency was affected by the subgroups of age, sex, completeness of suspension, ligature knot position and study design. Results indicated that fracture frequency was variable, there was no unique patterning, and high levels of heterogeneity were present in all variable sub-groups. Age was the only subgroup to show differences. Findings suggest that neck fracture frequency is inconsistent and cannot be predicted by the chosen variables. Subsequently, neck fractures in isolation should not be given weight in medico-legal interpretations of a hanging death as suicidal.

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.

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'.

A paleoepidemiological approach to the osteological paradox: Investigating stress, frailty and resilience through cribra orbitalia.

OBJECTIVES: The Osteological Paradox posits that skeletal lesions may differentially be interpreted as representing resilience or frailty. However, specific consideration of the etiologies and demographic distributions of individual skeletal indicators can inform the criteria on which to differentiate stress, frailty, and resilience. Adopting a life history approach and adaptive plasticity model, this study proposes a framework for the analysis and interpretation of a commonly reported skeletal lesion, cribra orbitalia, which considers the underlying mechanisms of the condition, the clinical and epidemiological literature relating to anemia and malnutrition, and the bioarcheological evidence. MATERIALS AND METHODS: Data were extracted from the European (n = 33 populations) and American (n = 19 populations) modules of the Global History of Health Project. Kaplan-Meier and Cox regression analyses were applied, where time was the age-at-death, and the factor or covariate was presence or absence of cribra orbitalia. RESULTS: Of 37 samples that produced significant results, 21 demonstrated a change in relationship when the subadults were excluded from analysis. When subadults were included, individuals with cribra orbitalia present had statistically significant lower survival time. With subadults excluded, the relationship either became nonsignificant or was reversed. DISCUSSION: We demonstrate that in many cases the inclusion of subadults in analysis impacts upon the apparent mortality associated with cribra orbitalia. Examining cribra orbitalia in children and adults has two separate goals: in children, to determine the prevalence and risk of death associated with active lesions and stress; and in adults, to determine whether childhood health assaults that cause cribra orbitalia are associated with frailty or resilience.

Corrigendum: Genetic identification of thiosulfate sulfurtransferase as an adipocyte-expressed antidiabetic target in mice selected for leanness.

This corrects the article DOI: 10.1038/nm.4115.

Sex, Parity, and Scars: A Meta-analytic Review.

The ability to identify whether a female has been pregnant or has given birth has significant implications for forensic investigations and bioarcheological research. The meaning of "scars of parturition," their causes, and their significance are a matter of contention, with a substantial literature of re-evaluations and tests of the relationship between pelvic scarring and parity. The aim of this study was to use meta-analytic techniques (the methodological approach) to test whether pelvic scarring, namely dorsal pubic pitting and the preauricular groove, is a predictor of parity and sex. Meta-analyses indicated that neither dorsal pubic pitting nor the preauricular groove are predictors of parity status, while dorsal pubic pitting is a moderate predictor of sex. A weak relationship between dorsal pubic pitting and parity was identified, but this is believed to be a product of the moderate relationship with sex. This calls into question whether any causal relationship between parity and pelvic scarring exists.

The D0-14/D ratio: A new paleodemographic index and equation for estimating total fertility rates.

OBJECTIVES: The objectives of this study were to develop a new subadult-adult ratio for application to sites with good infant representation and to produce an equation to estimate the total fertility rate for a population based on the age-at-death ratio. A new approach is required as current methods exclude the 0-4 years age category due to presumed underenumeration of infants. While this is true for some skeletal samples, others experience good infant representation. MATERIALS AND METHODS: Using age-at-death data and total fertility rates for 52 countries from the United Nations database for the year 1960, we examined the correlation between three age-at-death ratios and the fertility rate. We also utilized linear regression to determine an equation for calculating total fertility rate from the ratio. RESULTS: We achieved a correlation of 0.848 between our D0-14/D Ratio and actual fertility rates. This correlation was significantly higher (p < .05) than the other ratios examined, including the d5-14/d20+ by Bocquet-Appel and Masset () and the 15 P5 index by Bocquet-Appel (). DISCUSSION: The exclusion of infants can result in inaccurate demographic measures, particularly where subadults aged over 5 years of age experience robust survivorship. In addition to providing a solution for sites with good infant representation, this study indicates that the 0-4 years of age category possesses great predictive power when compared to other age categories. The regression equation provides a total fertility rate which is comparable with data regardless of their temporal origin. This method will provide more accurate demographic measures for bioarcheological sites with good infant preservation.

Genetic identification of thiosulfate sulfurtransferase as an adipocyte-expressed antidiabetic target in mice selected for leanness.

The discovery of genetic mechanisms for resistance to obesity and diabetes may illuminate new therapeutic strategies for the treatment of this global health challenge. We used the polygenic 'lean' mouse model, which has been selected for low adiposity over 60 generations, to identify mitochondrial thiosulfate sulfurtransferase (Tst; also known as rhodanese) as a candidate obesity-resistance gene with selectively increased expression in adipocytes. Elevated adipose Tst expression correlated with indices of metabolic health across diverse mouse strains. Transgenic overexpression of Tst in adipocytes protected mice from diet-induced obesity and insulin-resistant diabetes. Tst-deficient mice showed markedly exacerbated diabetes, whereas pharmacological activation of TST ameliorated diabetes in mice. Mechanistically, TST selectively augmented mitochondrial function combined with degradation of reactive oxygen species and sulfide. In humans, TST mRNA expression in adipose tissue correlated positively with insulin sensitivity in adipose tissue and negatively with fat mass. Thus, the genetic identification of Tst as a beneficial regulator of adipocyte mitochondrial function may have therapeutic significance for individuals with type 2 diabetes.

Revisiting the Phenice technique sex classification results reported by MacLaughlin and Bruce (1990).

Phenice (Am J Phys Anthropol 30 (1969):297-301) reported a success rate of 96% for his method of sex determination based on three morphological features of the pelvis. Numerous studies have tested and evaluated the method with affirmative results. The results of the study by MacLaughlin and Bruce (J Forensic Sci 35 (1990):1384-1392) were inconsistent with other studies, reporting far lower rates of accuracy and a greater degree of interobserver error. The authors believe that this may be the result of the inclusion of an "ambiguous" classification category. Revised modelling using forced classification of sex provides much higher classification rates with the implication that the poor results reported by MacLaughlin and Bruce were due to methodological error for the most part.