Deciduous enamel 3D microwear texture analysis as an indicator of childhood diet in medieval Canterbury, England

This study conducted the first three dimensional microwear texture analysis of human deciduous teeth to reconstruct the physical properties of medieval childhood diet (age 1-8yrs) at St Gregory's Priory and Cemetery (11th to 16th century AD) in Canterbury, England. Occlusal texture complexity surfaces of maxillary molars from juvenile skeletons (n=44) were examined to assess dietary hardness. Anisotropy values were calculated to reconstruct dietary toughness, as well as jaw movements during chewing. Evidence of weaning was sought, and variation in the physical properties of food was assessed against age and socio-economic status. Results indicate that weaning had already commenced in the youngest children. Diet became tougher from four years of age, and harder from age six. Variation in microwear texture surfaces was related to historical textual evidence that refers to lifestyle developments for these age groups. Diet did not vary with socio-economic status, which differs to previously reported patterns for adults. We conclude, microwear texture analyses can provide a non-destructive tool for revealing subtle aspects of childhood diet in the past

Socioeconomic status and survival in medieval Canterbury

The adverse urban environment of medieval Canterbury possibly influenced poor health conditions and diseases which ultimately led to death. Individuals of low socioeconomic status may have been more at risk of death than those of higher socioeconomic status due to dense living conditions, consistently encountering unhygienic waste management, and less access to resources during famines and disease outbreaks. This study evaluates survivorship and mortality risk patterns of high- and low-status groups to determine the effect of socioeconomic status on survival and mortality in medieval Canterbury. A sample of 796 low- and 74 high-status individuals were examined from St. Gregory’s Priory. Kaplan-Meier analysis and Cox Regression were used to assess mortality and survival between the socioeconomic status groups. The results reveal lower survivorship for high-status than low-status non-adults, and lower survivorship and high mortality risk for high-status adult females compared to low-status adult males. Meanwhile there were no significant differences found in mortality risks and survivorship between low- and high-status adult males, low- and high-status adult females, and low-status adult females and high-status adult males. High risk of mortality and decreased survivorship of high-status adult females may reflect decreased survivorship of high-status non-adults due to poor nutritional intake during and after pregnancy as well as rationing food. In comparison, low-status adult males would have benefited from the pilgrimage culture that allowed them abundant access to nutritious foods

Enamel thickness and growth rates in modern human permanent first molars over a 2000 year period in Britain

Objectives: This study explores variation and trends in first molar enamel thickness and daily enamel secretion rates over a 2000 year period in Britain. Methods: Permanent first molars (n=89) from the Roman, Anglo-Saxon, and Medieval periods, as well as modern day Britain, were analysed using standard histological methods. Relative enamel thickness (RET) and linear measurements of cuspal and lateral thickness were calculated for mesial cusps. Daily secretion rates (DSRs) were calculated for inner, mid, and outer enamel regions in both cuspal and lateral enamel. Significant differences and trends were identified between samples using non-parametric statistical tests. Results: Enamel thickness differed between some populations, but no temporal trends were identified. Early Anglo-Saxon molars had significantly thinner RET than both Late Anglo-Saxon (p<0.00) and Medieval (p<0.00) molars. Lateral enamel from the Roman molars was significantly thinner than the modern day sample (p=0.04). In contrast, DSRs slowed significantly from the more ancient to the modern day samples in every comparison except the mid lateral enamel region. Discussion: This study presents the first evidence for a gradual slowing in the daily rate that enamel is secreted in molars over the past 2000 years in Britain. However, this trend was not matched by a change in enamel thickness, which remained fairly consistent over this time period. These findings suggest that modern human molars of similar enamel thickness, from different modern and ancient populations, formed at different rates

Inter-population differences in enamel secretion rates: a comparison between modern and ancient populations

Human enamel growth occurs as ameloblast cells secrete and mineralize protein matrix. Studies of enamel daily secretion rates (DSRs) have yielded significant insights into the evolution of permanent tooth enamel across hominin species. However, inter-population variation of modern human permanent enamel DSRs has received less attention, particularly for anterior tooth types. This study utilizes dental histological thin sections to examine DSRs calculated for lateral and cuspal enamel regions for permanent molar, canine, and incisor crowns from British populations. These samples date from the Roman (70-400AD), Early-Anglo Saxon (500-600AD), Late Anglo- Saxon (800-1200AD), Medieval (1100-1500AD), and modern day period. A total of 338 teeth were analyzed: molar (n=89), canine (n=69), incisor (n=80). Results display consistent and significant trends towards decreasing DSRs from the ancient to modern populations. This was observed in all molar cuspal (p<0.00), lateral mid (p<0.01) and outer (p<0.00) regions, in all incisor cuspal and lateral regions (all p<0.00), and in all canine cuspal and lateral regions (all p<0.00). These data provide the first evidence for a change in the daily rate of enamel growth in human permanent dentition, in multiple permanent tooth types, over a 2000 year period. This alludes to a previously unidentified plasticity in modern human enamel growth. Ongoing research will investigate whether similar variation has occurred in other enamel variables over this period of time in these populations

Bone deep: variation in stable isotope ratios and histomorphometric measurements of bone remodelling within adult humans

Stable carbon (?13C) and nitrogen (?15N) isotope studies of ancient human diet increasingly sample several skeletal elements within an individual. Such studies draw upon differences in bone turnover rates to reconstruct diet during different periods of time within an individual’s lifetime. Rib and femoral bone, with their respectively fast and slow remodeling rates, are the bones most often sampled to reconstruct shorter and longer term signals of diet prior to death. It is poorly understood if ?13C and ?15N vary between bone types within a single individual, or if this variation corresponds with bone turnover rate (BTR). Here, we determined ?13C and ?15N for ten different bones from ten adult human skeletons (n=5 males; n=5 females). Isotope values were compared to the rate that each bone remodeled, calculated from osteon population (OPD) density. Results reveal that isotope ratios varied within each skeleton (?13C: max= -1.58‰; ?1542 N: max= 3.05‰). Humeri, metacarpals, and ribs had the highest rate of bone remodelling; the occipital bone had the lowest. A regression analyses revealed that higher rates of bone remodeling are significantly and negatively correlated with lower ?15N. Our results suggest that the occipital bone, with its slow rate of bone renewal, may prove useful for isotopic studies that reconstruct diet over longer periods of time within an individual’s lifetime. Isotope studies that compare individual skeletal elements between populations should standardize their methodology to bones with either a slow or fast turnover rate

Enamel biorhythms of humans and great apes: the Havers-Halberg Oscillation hypothesis reconsidered

The Havers-Halberg Oscillation (HHO) hypothesis links evidence for the timing of a biorhythm retained in permanent tooth enamel (Retzius periodicity) to adult body mass and life history traits across mammals. Potentially, these links provide a way to access life history of fossil species from teeth. Recently we assessed intra-specific predictions of the HHO on human children. We reported Retzius periodicity (RP) corresponded with enamel thickness, and cusp formation time, when calculated from isolated deciduous teeth. We proposed the biorhythm might not remain constant within an individual. Here, we test our findings. RP is compared between deciduous second and permanent first molars within the maxillae of four human children. Following this, we report the first RPs for deciduous teeth from modern great apes (n = 4), and compare these with new data for permanent teeth (n = 18) from these species, as well as with previously published values. We also explore RP in teeth that retain hypoplastic defects. Results show RP changed within the maxilla of each child, from thinner to thicker enameled molars, and from one side of a hypoplastic defect to the other. When considered alongside correlations between RP and cusp formation time, these observations provide further evidence that RP is associated with enamel growth processes and does not always remain constant within an individual. RP of 5 days for great ape deciduous teeth lay below the lowermost range of those from permanent teeth of modern orangutan and gorilla, and within the lowermost range of RPs from chimpanzee permanent teeth. Our data suggest associations between RP and enamel growth processes of humans might extend to great apes. These findings provide a new framework from which to develop the HHO hypothesis, which can incorporate enamel growth along with other physiological systems. Applications of the HHO to fossil teeth should avoid transferring RP between deciduous and permanent enamel, or including hypoplastic teeth

Improved visualization of decomposing tattoos using optical coherence tomography

Tattoos can be used in forensic human identification as a secondary means of identification (other means being, but not limited to, personal descriptions and artefacts) allowing the identification procedure to be strengthened in this way. Despite this, the decomposition of tattoos is a topic not extensively studied in taphonomic research (study of how organisms decay). In this communication, we assess optical coherence tomography (OCT) as a method to reliably identify tattoos before and after decomposition, by imaging tattooed porcine samples. OCT was able to penetrate up to 3mm below the surface and visualize parts of tattoos after 16 days of decomposition, which were no longer visible and recognizable using conventional photography-based methods. We believe this imaging modality has the potential to increase the reliability of tattoos in forensic human identification

Enamel growth rates of anterior teeth in males and females from modern and ancient British populations

Objectives: This study explored biological sex differences in the regional daily growth rates of human anterior enamel from modern and ancient populations in Britain.Methods: Maxillary permanent incisors (n=80) and canines (n=69) from Roman, Anglo-Saxon, Medieval, and Modern day populations were analysed using histological methods. Daily secretion rates (DSRs) were collected for inner, mid, and outer regions of cuspal and lateral enamel. Modern day samples were of known sex, archaeological individuals had sex determined using standard osteological methods. Variation in DSRs between the sexes, both between and within populations, was sought using parametric and non-parametric tests.Results: When all samples were pooled, there was no significant difference between males and females. Similarly no significant differences in DSRs were identified between male and females within each population. When DSRs were compared between the populations, DSRs decreased from the more ancient to the more recent populations for males, and for females. More inter-population differences were observed in males.Discussion: This study presents evidence for the relative consistency of enamel DSRs between male and female groups within each British population. Inter-population analyses found DSRs slowed significantly between Roman and modern day populations for both sexes, with male DSRs showing the greatest variation between populations