Correcting the Record on the Pembrokeshire Cow

Our baffled blogger friend is confused by the science of the analysis of the now famous cow tooth, unfortunately he then uses that inability to comprehend to spread misinformation. Here is my very quick, simplified analysis which might help correct the record.

The key is this figure;

Click to enlarge

Figure 6 from the paper "Sequential multi-isotope sampling through a Bos taurus tooth from Stonehenge: Investigating cattle mobility in the Neolithic" by Evans et al. (2025), published in the Journal of Archaeological Science https://doi.org/10.1016/j.jas.2025.106269 . It illustrates lead (Pb) isotope data in μ (^{238}U/^{204}Pb) versus T (model age in Ma) space for sequential enamel samples from a Neolithic cow's third molar (M3), dated to approximately 3350–2920 BCE, excavated from Stonehenge's ditch.

Description and Verification of the Diagram

• Axes and Layout: The y-axis shows μ ranging from 9.50 to 9.90. The x-axis shows T from 100 to 500 Ma (increasing rightward). This format aligns with UK Pb isoscape conventions, where older T values (higher on the x-axis) correspond to ancient geological terrains like the Avalonian basement in Wales, and younger T values to later events like Hercynian mineralisation in southern England.
• 1SD Ranges (Boxes):
  • Left box: "1SD range of English ore from Pennines, Mendips and SW England" – Centred around T ≈ 200–300 Ma, μ ≈ 9.75–9.85, reflecting younger, uranium-enriched (higher-μ) Hercynian ores dominant in central and southern England.
  • Right box: "1SD range for Pb ore from Wales" – Centred around T ≈ 400–500 Ma, μ ≈ 9.65–9.75, capturing older, less uranium-enriched (lower-μ) signatures from Welsh Avalonian basement and associated ore fields (e.g., Malvern Complex).
  • Bottom box: "1SD range for Pb ores from Southern Uplands Scotland" – At T ≈ 100–150 Ma, μ ≈ 9.55, highlighting distinct Caledonian signatures north of the Iapetus Suture.
• Trajectory Path and Arrows: The arrows denote the chronological sequence of enamel slices from earliest (crown, winter) to latest (root/cervix, summer). In hypsodont cattle molars, enamel forms incrementally over ~6–18 months post-birth, capturing time-resolved environmental and physiological signals.
• Labels with Question Marks:
  • Left circle: "dietary source?" – Proposes the initial Pb signal derives primarily from local dietary intake (e.g., fodder, water, or soil ingestion in the Wiltshire/Stonehenge Chalk area, consistent with nearby English ore influences like the Mendips).
  • Right circle: "skeletal source?" – Suggests the later shift reflects remobilised Pb from the cow's skeletal reserves, potentially triggered by metabolic stress (e.g., calving, lactation, or being used as a beast of burden), overriding contemporary dietary inputs. And then the trajectory returns to the dietary sources.

This diagram is constructed from raw Pb isotope ratios (^{206}Pb/^{204}Pb, ^{207}Pb/^{204}Pb, ^{208}Pb/^{204}Pb) measured via MC-ICP-MS on the nine slices, converted to μ and T using the Albarède et al. (2012) method, and plotted against 1SD ore reference fields (excluding 10% outliers for robustness). Complementary Sr isotopes show a unidirectional decrease from 0.7144 (winter, radiogenic, consistent with western Britain/old rocks) to 0.7110 (summer, less radiogenic, Chalk-like), while Pb concentrations fluctuate with peaks and troughs, decoupling from Sr.

Interpretation in the Paper

The trajectory indicates complex Neolithic cattle husbandry, potentially tied to Welsh-Stonehenge connections (e.g., bluestone transport via livestock haulage). The Pb shift from English-like (higher-μ, younger-T) to Welsh-like (lower-μ, older-T) signatures is not solely attributed to geographic mobility but to a mix of dietary Pb (geogenic from local environments) and skeletal remobilisation. During stress, stored skeletal Pb—from early life exposure to Welsh-like sources—can enter the bloodstream and incorporate into forming enamel, decoupling Pb from Sr (which remains dietary). This echoes prior UK isoscape work, supporting Welsh origins or exposure for the cow's early life. Other factors may include foddering across landscapes or seasonal changes. The paper concludes this provides the first isotopic evidence of Neolithic cattle mobility linked to Wales, enhancing theories of long-distance networks, though physiological drivers must be considered.

Simplified Explanation of How Model Ages (T) Are Calculated

Model ages T for Pb isotopes estimate the time (in Ma) since Pb was last separated from its uranium (U) and thorium (Th) parent elements in source rocks, based on measured isotope ratios. It's a numerical solution to a system of equations assuming single-stage evolution from primordial Pb:

1. Measure ratios like ^{206}Pb/^{204}Pb, ^{207}Pb/^{204}Pb, and ^{208}Pb/^{204}Pb.
2. Use starting primordial values (e.g., from meteorites) and decay constants for U and Th.
3. Solve iteratively (via software) for T, μ (^{238}U/^{204}Pb), and κ (^{232}Th/^{238}U) that best fit the data, e.g.:
   • ^{206}Pb/^{204}Pb = initial + μ (e^{λ_{238} T} - 1) (Similar for 207 and 208, adjusted for isotopes.) This links signatures to geological history, with older T for ancient basements like Wales (~460 Ma) versus younger for England (~300 Ma).

For the Stonehenge cow, the Welsh-like Pb signature, older T, in enamel slices suggests early-life exposure to such elevated-Pb Welsh terrains, with skeletal stores potentially remobilised during stress, amplifying incorporation beyond typical dietary levels. While modern validations use animals from Welsh mining districts where historical mining pollution may augment Pb concentrations, the isotopic compositions closely match geogenic ore signatures, indicating that natural processes dominated in the Neolithic and that mining effects do not fundamentally alter the provenance interpretation.

For more details see also:  Applying lead (Pb) isotopes to explore mobility in humans and animals
Evans JA, Pashley V, Mee K, Wagner D, Parker Pearson M, et al. (2022) Applying lead (Pb) isotopes to explore mobility in humans and animals. PLOS ONE 17(10): e0274831. https://doi.org/10.1371/journal.pone.0274831