Patterns of dental enamel defects at ancient Mendes, Egypt

Hidden in plain text: Uncovering hidden heterogeneity and social stratification in Ireland AD 1150-1800

OBJECTIVES

Between the Irish late medieval (AD 1150-c.1550) (LMP) and post-medieval (AD c.1550-1800) (PMP) periods, colonial practices changed land ownership. Contextualizing these periods within a biocultural political economy framework supports increasing social inequality in the PMP, which we expect to be reflected in different skeletal markers of longevity and stress. Therefore, we hypothesized that widespread exposure to stressors and resource deprivation contributed to lower longevity in the PMP compared to the LMP, and that there would be greater variation between sites in the frequency of linear enamel hypoplasias (LEH) in the PMP.

MATERIALS AND METHODS

We estimated age and counted matched pairs of LEH on 526 adult skeletons from the Irish counties of Dublin, Kildare, Louth, and Meath. Age-at-death was compared through Kaplan-Meier survival functions and non-parametric tests. Linear enamel hypoplasias prevalences were analyzed with Mann-Whitney U tests and Generalized Linear Models.

RESULTS

Age-at-death distribution changed between the LMP and PMP for males, with males experiencing an increase in median-age-at-death. The same was untrue for females, who show no changes in median age-at-death. Analysis of LEH frequency per individual showed that variation between sites was significant in the post-medieval period but not in the late medieval period.

CONCLUSION

These results suggest that social organization contributed to embodied health experiences that varied across time periods. Specifically, populations from the PMP appear to have embodied greater social inequality in their more varied susceptibility to stress. Our work demonstrates the strength of pairing historical texts with the analysis of skeletal remains to evaluate the impact of social structures on biological frailty.

Assessing weaning stress - Relations between enamel hypoplasia, δ18O and δ13C values in human teeth obtained from early modern cemeteries in Wroclaw, Poland

OBJECTIVES

The aim of this paper is to assess linear enamel hypoplasia (LEH) on canines of adults from early modern Wroclaw cemeteries to compare δ¹³C and δ¹⁸O values in enamel formed before, during and after LEH formation, and to attempt to find a link between the selected indicators of the weaning process.

MATERIAL AND METHODS

15 permanent canines with visible LEH were selected for analysis. Age at LEH formation was estimated using the Reid and Dean method. The perikymata count was used to estimate the duration of LEH formation. Incremental stable oxygen and carbon isotopes analysis was performed on tooth enamel to infer stress related to weaning and dietary patterns. Kruskal-Wallis ANOVA, Mann-Whitney U test and Spearman correlation were used in statistical inference.

RESULTS

The average age of LEH formation was 3.14 years, with an average duration of 111 days. Stable carbon isotope values consistently increase in 73% of the individuals sampled. The values of δ¹⁸O do not show a dominant pattern. The average value of δ¹³C increases over the time of enamel formation. The δ¹³C values collected below LEH were negatively correlated with δ¹⁸O values and the duration of LEH termination.

CONCLUSIONS

Marking of carbon and oxygen isotopes indicates different stages of weaning. Advancements in diet change (determined by higher δ¹³C) corresponds with faster recovery after physiological stress episode. There is no evidence for different breastfeeding models between distinct parishes in early modern Wroclaw.

Dental indicators of health and stress in early Egyptian and Nubian agriculturalists: A difficult transition and gradual recovery

Although agriculture is now the globally predominant mode of food production, studies of the skeletal remains of early agriculturalists have indicated high levels of physiological stress and poor health relative to hunter-gatherers in similar environments. Previous studies identifying this trend in different regions prompt further research of the causes and effects of subsistence transitions in human societies. Here, 242 dentitions from five ancient Egyptian and Nubian populations are examined: 38 individuals from Jebel Sahaba (Upper Paleolithic), 56 from Badari (Predynastic), 54 from Naqada (Predynastic), 47 from Tarkhan (Dynastic), and 47 from Kerma (Dynastic). These populations span the early period of agricultural intensification along the Nile valley. Skeletal remains were scored for the presence of linear enamel hypoplasia (LEH) of the dentition, an established indicator of physiological stress and growth interruption. The prevalence of LEH was highest in the "proto-agricultural" (pastoralist) Badari population, with a gradual decline throughout the late Predynastic and early Dynastic periods of state formation. This suggests that the period surrounding the emergence of early agriculture in the Nile valley was associated with high stress and poor health, but that the health of agriculturalists improved substantially with the increasing urbanization and trade that accompanied the formation of the Egyptian state. This evidence for poor health among proto- and early agriculturalists in the Nile valley supports theories that agricultural intensification occurred as a response to ecological or demographic pressure rather than simply as an innovation over an existing stable subsistence strategy.

Isotopic evidence for age-related immigration to imperial Rome

Oxygen stable isotope ratios (delta(18)O) have been determined in carbonate in paired first and third molar teeth from individuals (N = 61) who lived in the town of Portus Romae ("Portus") and who were buried in the necropolis of Isola Sacra (First to Third centuries AD) near Rome, Italy. We compare these analyses with data for deciduous teeth of modern Roman children. Approximately one-third of the archaeological sample has first molar (M1) values outside the modern range, implying a large rate of population turnover at that time, consistent with historical data. Delta (18)O(ap) values suggest that a group within the sample migrated to the area before the third molar (M3) crown had completely formed (i.e., between 10 and 17.5 years of age). This is the first quantitative assessment of population mobility in Classical antiquity. This study demonstrates that migration was not limited to predominantly single adult males, as suggested by historical sources, but rather a complex phenomenon involving families. We hypothesize that migrants most likely came from higher elevations to the East and North of Rome. One individual with a higher delta(18)O value may have come (as a child) from an area isotopically similar to North Africa.

Health of infants in an Imperial Roman skeletal sample: Perspective from dental microstructure

This study examines general health in the first year of life of a population of 127 subadults from the Imperial Roman necropolis of Isola Sacra (2nd-3rd century ACE). Health status was determined by analyzing 274 deciduous teeth from these children for Wilson bands (also known as accentuated striae), microscopic defects caused by a disruption to normal enamel development arising from some generalized external stressor. While macroscopic enamel defects, or hypoplasias, have long been used as proxies of general population health, we believe that this is the first population-wide study of microscopic defects in deciduous teeth. We used microstructural markers of enamel to attach very precise chronologies to Wilson band formation that allowed us to calculate maximum prevalence (MAP) and smoothed maximum prevalence (SMAP) distributions to portray what we believe to be a realistic risk profile for a past population of children. There appear to be two periods of high prevalence, the first beginning around age 2 months and continuing through month 5, and the second higher period beginning around month 6 and continuing through month 9. These results are discussed in light of historical records of Roman childhood rearing practices.

Linear enamel hypoplasias as indicators of systemic physiological stress: evidence from two known age-at-death and sex populations from postmedieval London

Enamel hypoplasias are useful indicators of systemic growth disturbances during childhood, and are routinely used to investigate patterns of morbidity and mortality in past populations. This study examined the pattern of linear enamel hypoplasias in two different burial populations from 18th and 19th Century church crypts in London. Linear enamel hypoplasias on the permanent dentitions of individuals from the crypt of Christ Church, Spitalfields, were compared to enamel defects on the teeth of individuals from St. Bride's. The method used involves the identification of enamel defects at a microscopic level, and systemic perturbations are detected by matching hypoplasias among different tooth classes within each individual. The pattern of linear enamel hypoplasias was contrasted between individuals from the burial sites of Spitalfields and St. Bride's, between males and females, and between those aged less than 20 years of age and those aged over 20 years at death. Six different parameters were examined: frequency of linear enamel hypoplasias, interval between defects, duration of hypoplasias, age at first occurrence of hypoplasia, age at last occurrence of hypoplasia, and the percentage of enamel formation time taken up by growth disturbances. All individuals in the study displayed linear enamel hypoplasias, with up to 33% of total visible enamel formation time affected by growth disruptions. Multiple regression analysis indicated a number of significant differences in the pattern of enamel hypoplasias. Individuals from Spitalfields had shorter intervals between defects and greater percentages of enamel formation time affected by growth disturbances than did individuals from St. Bride's. Females had greater numbers of linear enamel hypoplasias, shorter intervals between defects, and greater percentages of enamel formation time affected by growth disturbances than males. There were also differences in the pattern of enamel hypoplasias and age at death in this study. Individuals who died younger in life had an earlier age at first occurrence of enamel hypoplasia than those who survived to an older age. The pattern of enamel hypoplasias detected in this study was influenced by tooth crown geometry and tooth wear such that most defects were found in the midcrown and cervical regions of the teeth, and greater numbers of defects were identified on the anterior teeth. Differences in sensitivity of the parameters used for the detection of enamel hypoplasias were found in this study. The percentage of visible enamel formation time affected by growth disturbances was the parameter that identified the greatest number of significant differences among the subgroups examined.