Lower first molar enamel (87Sr/86Sr, δ18O) and associated mandibular bone (δ13C, δ15N, and δ34S) were sampled (table S1). In some instances, it was necessary to sample other teeth. All 87Sr/86Sr, δ18O, and δ34S isotope analyses were undertaken at the Natural Environment Research Council (NERC) Isotope Geosciences Laboratory (NIGL), Keyworth. The enamel surface of each tooth was abraded to a depth of >100 μm using a tungsten carbide dental burr, and the residue was discarded. Thin enamel slices (1 to 2 mm in breadth) were then cut from the tooth using a flexible diamond-edged rotary wheel attached to an Argofile PS220 precision drill. All surfaces were mechanically cleaned with a diamond burr to remove adhering dentine. For 87Sr/86Sr isotope analysis, samples were transferred to a clean (class 100, laminar flow) area, washed in high-purity acetone, cleaned ultrasonically, dried, and weighed into Teflon beakers. The samples were mixed with 84Sr tracer solution and dissolved in Teflon-distilled 8 M HNO3. Strontium was collected using Dowex resin columns. Strontium was loaded onto a single Re filament with TaF (Tantalum emitter), and the isotope values and concentrations were determined by thermal ionization mass spectrometry using a Thermo Triton multicollector mass spectrometer. The international standard for 87Sr/86Sr, NBS987, gave a value of 0.710255 ± 0.000012 (n = 68, 2σ) during analysis. Blank values were in the region of 100 pg. The carbonate fraction of dental enamel was sampled for δ18O isotope analysis. In all instances, the same tooth was sampled as for 87Sr/86Sr isotope analysis. Clean enamel was powdered, weighed (2 mg ± 0.5 mg), loaded into glass vials, sealed with septa, and transferred to a hot block (90°C) on a MultiPrep system. Vials were evacuated, and four drops of anhydrous phosphoric acid were added. The resultant CO2 was collected cryogenically for 15 min and transferred to a GV IsoPrime dual inlet mass spectrometer. The resultant isotope values are reported as per mil (‰) normalized to the Vienna Pee Dee belemnite (VPDB) scale using an in-house carbonate reference material (KCM: Keyworth Carrara Marble) calibrated against an NBS19-certified reference material. The δ18O carbonate values were then converted into the Vienna standard mean ocean water (VSMOW) scale [VSMOW = 1.0309 × δ18O VPDB + 30.91 (39)]. The batch reproducibility for δ18O KCM was ±0.09‰ (1σ). A total of 39 samples were analyzed in duplicate, providing a mean SD (1σ) for replicate samples of 0.13‰.

The collagen extraction protocol followed a modified Longin method. Bone or dentine (approximately 0.5 g for bone and 0.1 to 0.4 g for dentine) was cleaned using a diamond burr, demineralized in 8 ml of 0.5 M HCl at 4°C, and gelatinized in HCl (pH 3) at 70°C for 48 hours. The supernate was collected using an 8-μm Ezee filter and transferred to polypropylene tubes for freeze-drying. For δ34S isotope analysis, V2O5 was added to aid combustion. Samples were processed in duplicate as a minimum, but in some instances, four replicates were analyzed to ensure reliable repeats. There was one exception to this, sample WK120, which produced insufficient collagen for replicate analysis. Isotope ratios were measured by continuous flow–elemental analysis–isotope ratio mass spectrometry. δ34S isotope analysis was undertaken at NIGL, Keyworth. δ13C and δ15N isotope analyses were undertaken at Cardiff University, NIGL (Keyworth), and the University of Cambridge. Details of the instrumentation, standards, and reproducibility are provided in the Supplementary Materials. Collagen δ13C, δ15N, and δ34S isotope values are reported in per mil (‰) relative to VPDB, AIR, and VCDT (Vienna Canyon Diablo Troilite) standards, respectively.

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