Review: Mobility of Interred Individuals at Neolithic Tombs in Wales Using Sulfur (δ³⁴S) Bone Collagen Isotope Values and a Predictive Archaeological Sulfur Isoscape for the UK

Damon Tarrant, Richard Madgwick, Leïa Mion, Angela Lamb, Alasdair W. R. Whittle, Michael P. Richards; Mobility of interred individuals at Neolithic tombs in Wales using sulfur (δ34S) bone collagen isotope values and a predictive archaeological sulfur isoscape for the UK. R Soc Open Sci. 1 January 2026; 13 (1): 251696. https://doi.org/10.1098/rsos.251696

This paper by Tarrant et al. represents a very interesting and potentially groundbreaking contribution to Neolithic archaeology in Britain. It focuses on using sulfur isotope (δ³⁴S) analysis of bone collagen from 27 individuals buried in five early Neolithic tombs in south Wales (Heston Brake, Parc le Breos Cwm, Penywyrlod, Tinkinswood, and Ty Isaf) to infer mobility and dietary patterns during adulthood. By developing a novel predictive sulfur isoscape for the UK based on archaeological faunal data, the authors provide a framework for interpreting these values against regional baselines. While the study is preliminary and rightly cautious in its interpretations—acknowledging assumptions about baselines and the need for larger datasets—it lays a solid foundation for future research in isotope-based mobility studies.

(A) δ34S isoscape of the UK using faunal collagen. (B). δ34S faunal error isoscape of the UK. Circles represent site locations for the collagen sulfur data.

The methodology is innovative, employing random forest regression to create a high-resolution δ³⁴S isoscape from median values of 735 faunal collagen samples across 38 UK sites. This model incorporates environmental predictors like mean annual precipitation (a key driver, explaining ~60% of variation) and bedrock geology, achieving a respectable R² of 0.82 and a mean prediction error of ~4‰. Human δ³⁴S values (ranging from 11.2‰ to 17.7‰) are then compared to this isoscape using the R package 'AssignR' to assess 'local' versus 'non-local' origins. The approach complements earlier strontium isotope work on the same sites, which reflects childhood mobility, allowing for a more holistic view of life histories.

The results are intriguing and challenge some preconceptions about Neolithic lifeways in Wales. All individuals appear broadly local to Wales, aligning with genetic evidence of continental migration during the Neolithic transition. However, four of the five tombs include potential non-locals to their specific regions—for instance, some at Parc le Breos Cwm may originate from further east, while higher values at Ty Isaf and Penywyrlod suggest shifts between coastal and inland areas. Notably, despite the coastal settings of several sites such as Parc le Breos Cwm, there is no evidence for substantial marine dietary input or strong coastal sulfur enrichment (e.g., from sea-spray influence), reinforcing previous carbon and nitrogen isotope results that indicate predominantly terrestrial subsistence. This absence of marine influence is particularly fascinating, hinting at cultural or economic preferences in food procurement during the fourth millennium cal BC.

The study's caution is commendable, especially in comparing the archaeological collagen isoscape to a modern plant-based one, which reveals discrepancies potentially due to anthropogenic changes like pollution or landscape alterations affecting soil sulfur cycles. Linking sulfur (adult mobility) with strontium (childhood) opens avenues for exploring lifecycle movements, such as potential exogamy or resource exchange networks.

That said, reliance on data from midden sites (e.g., Potterne, All Cannings Cross, Stanton St Bernard, and East Chisenbury) raises some concerns, as these Late Bronze Age/Early Iron Age accumulations often include non-local animals mobilised through feasting networks—pigs, in particular, show isotopic evidence of distant origins in prior studies. This could skew baselines, especially given high intra-site variations (e.g., Potterne's s.d. of 10.3‰). However, the use of medians per site largely overcomes this by downweighting outliers, assuming the majority reflect local signals. The model's environmental smoothing further mitigates site-specific noise, though spatial gaps in faunal data (e.g., fewer Welsh sites) introduce moderate uncertainty.

For once, the call for 'more research needed' feels wholly justified rather than rote. Expanding the dataset with temporally matched faunal samples and integrating it with strontium, oxygen, and even ancient DNA across the rest of the UK could yield fascinating insights into Neolithic population dynamics, trade, and social structures. This paper is a promising step forward, blending biogeochemistry with archaeology to illuminate Britain's prehistoric past.