North and South: Exploring isotopic analysis of bone carbonates and collagen to understand post-medieval diets in London and northern England

OBJECTIVES

We evaluate the potential of paired isotopic analysis of bone carbonate and collagen to examine the diet of post-medieval human and animal populations from England (17th-19th c.), including, for the first time, manufacturing towns in northern England. The potential for identifying C4 crop consumption is explored alongside regional and local patterning in diet by sex and socioeconomic status.

MATERIALS AND METHODS

Humans (n = 216) and animals (n = 168) were analyzed from sites in London and northern England for both carbon and nitrogen isotopes of bone collagen (𝛿13 Ccoll , 𝛿15 Ncoll ). Isotopic analysis of bone carbonates (𝛿13 Ccarb , 𝛿18 Ocarb ) was carried out on all humans and 27 animals, using Fourier transform infrared spectroscopy-attenuated total reflectance to assess diagenesis.

RESULTS

Variations in diet were observed between and within different populations by geographical location and socioeconomic status. Three pigs and one cow consumed C4 resources, indicating the availability of C4 -fed animal protein. Londoners consumed more animal and marine protein and C4 resources. Middle- and upper-class populations from both London and northern populations also had greater access to these foods compared to those of lower status in the same regions.

DISCUSSION

This substantial multi-isotope dataset deriving from bone carbonate and collagen combined from diverse post-medieval urban communities enabled, for the first time, the biomolecular identification of the dynamics of C4 consumption (cane sugar/maize) in England, providing insight into the dynamics of food globalization during this period. We also add substantially to the animal dataset for post-medieval England, providing further insight into animal management during a key moment of agricultural change.

Isotope analysis of human dental calculus δ13 CO3 2- : Investigating a potential new proxy for sugar consumption

RATIONALE

Dental calculus (mineralised dental plaque) is composed primarily of hydroxyapatite. We hypothesise that the carbonate component of dental calculus will reflect the isotopic composition of ingested simple carbohydrates. Therefore, dental calculus carbonates may be an indicator for sugar consumption, and an alternative to bone carbonate in isotopic palaeodiet studies.

METHODS

We utilised Fourier transform infrared attenuated total reflectance analysis to characterise the composition and crystallisation of bone and dental calculus before isotope analysis of carbonate. Using a Sercon 20-22 mass spectrometer coupled with a Sercon GSL sample preparation system and an IsoPrime 100 dual inlet mass spectrometer plus Multiprep device to measure carbon, we tested the potential of dental calculus carbonate to identify C₄ resources in diet through analysis of δ¹³ C values in paired bone, calculus and teeth mineral samples.

RESULTS

The modern population shows higher δ¹³ C values in all three tissue carbonates compared to both archaeological populations. Clear differences in dental calculus δ¹³ C values are observed between the modern and archaeological individuals suggesting potential for utilising dental calculus in isotope palaeodiet studies. The offset between dental calculus and either bone or enamel carbonate δ¹³ C values is large and consistent in direction, with no consistent offset between the δ¹³ C values for the three tissues per individual.

CONCLUSIONS

Our results support dental calculus carbonate as a new biomaterial to identify C₄ sugar through isotope analysis. Greater carbon fractionation in the mouth is likely due to the complex formation of dental calculus as a mineralized biofilm, which results in consistently high δ¹³ C values compared to bone and enamel.