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

Social weaning: childhood diet and health in medieval Canterbury, UK

Food consumption during the medieval period is understood mainly from adult diet, higher status families, and monastic communities. By contrast, there is little direct evidence for foods consumed by children, or whether their diet corresponded with health and status. Here, we address these questions in skeletal samples from the medieval city of Canterbury. We undertake the first comprehensive intra-specific microwear texture analysis of childhood diet (n=51) and integrate this with histological ‘snap-shots’ of general health from enamel accentuated markings (n=71). An adult comparative sample (n=11) is included. Microwear texture complexity values increased from age 1 to 4yrs while anisotropy values decreased suggesting that foods became harder and required more varied jaw movements during chewing. The 4.1-6 year olds had a significantly lower mean complexity value than younger children. Complexity values increased again while anisotropy decreased in 6.1-9 year olds. Prevalence of accentuated markings peaked at 6 months, early in the second year, and just before age 4yrs. Diet did not relate to childhood status, and adults consumed a greater range of softer and harder foods. Health of the youngest children likely relates to an immature immune system. Correspondence between a softer diet and improved health around age 4yrs may indicate the start of ‘social weaning’. Textual evidence refers to lifestyle changes from this age onwards, as children undertook household chores and then work outside the home. This might have provided less opportunity for early childhood dietary staples contaminated with grit, and initially introduced a softer but more nutritious adult food

Population collapses in introduced non-indigenous crayfish

Invasive species often have instable population dynamics and are known to collapse or oscillate heavily after passing through the initial lag/growth phases. Long-term data-series documenting these fluctuations are however rare. We use long-term (starting in the early 1960s), semi-quantitative data on the invasive signal crayfish (Pacifastacus leniusculus), capturing its population development after introduction in 44 Swedish lakes. In total 18 (41 %) of these populations had experienced a collapse. A stepwise discriminant function analysis including 20 different ecological or physicochemical characteristics identified three variables explaining collapses in the following order: stocking year, population age and mean air temperature. Populations stocked in the 1980s were more likely to collapse than populations stocked in the 1970s. Lakes with collapses were located in areas with 0.4 A degrees C higher yearly mean air temperatures than the still viable populations. Collapses also depended on the time phase of the population and started to occur 12 years after stocking and were most frequent in the interval 16-20 years after stocking and after 11-15 years duration of the established phase with harvestable densities. An analysis of prevalence and pathogen load of Aphanomyces astaci was conducted in eight of the studied populations. A. astaci was present in all populations but neither the level of prevalence nor the pathogen load in infested specimens differed significantly between lakes with collapses and lakes without. Our results highlight the potential sensitivity and instability of introduced crayfish. The importance of density-dependence and temperature suggest that both climate variability and/or fisheries can influence these processes