Strontium isotope (⁸⁷Sr/⁸⁶Sr) analysis with reference to strontium isotope landscapes (Sr isoscapes) allows reconstructing mobility and migration in archaeology, ecology, and forensics. However, despite the vast potential of research involving ⁸⁷Sr/⁸⁶Sr analysis particularly in Africa, Sr isoscapes remain unavailable for the largest parts of the continent. Here, we measure the ⁸⁷Sr/⁸⁶Sr ratios in 778 environmental samples from 24 African countries and combine this data with published data to model a bioavailable Sr isoscape for sub-Saharan Africa using random forest regression. We demonstrate the efficacy of this Sr isoscape, in combination with other lines of evidence, to trace the African roots of individuals from historic slavery contexts, particularly those with highly radiogenic ⁸⁷Sr/⁸⁶Sr ratios uncommon in the African Diaspora. Our study provides an extensive African ⁸⁷Sr/⁸⁶Sr dataset which includes scientifically marginalized regions of Africa, with significant implications for the archaeology of the transatlantic slave trade, wildlife ecology, conservation, and forensics.

Strontium isotopes ( ⁸⁷ Sr/ ⁸⁶ Sr) are increasingly used as a provenance tool in multiple disciplines. Application to biological materials requires knowledge of the variation in bioavailable ⁸⁷ Sr/ ⁸⁶ Sr across the landscape, potentially in the form of an isoscape (a quantitative model of spatial isotopic variability). This paper summarizes and provides advice on our current understanding of the main concerns in creating and interpreting isoscapes of bioavailable ⁸⁷ Sr/ ⁸⁶ Sr. Isoscape creation approaches include domain mapping, geostatistical contour mapping and machine learning, the last becoming more readily achievable with the availability of software packages. It is critically important to develop isoscapes at a resolution appropriate for addressing the research questions. Choice of sample materials depends on the research questions and availability: plants or fauna with small ranges are favoured, with some analytes (snails, soil leachates) posing challenges. Interpreting ⁸⁷ Sr/ ⁸⁶ Sr in biological tissues requires considering Sr metabolism and the timing of tissue formation, thus far underappreciated. The numerous sources of error involved in developing and applying isoscapes must be recognized to avoid over-interpreting data and spurious provenance precision. We hope this paper will help researchers investigating provenance, mobility, landscape use and migration to develop the most appropriate isoscapes for their purposes, and possible future use by others.

The canopy effect describes vertical variation in the isotope ratios of carbon (δ¹³C), oxygen (δ¹⁸O) and partially nitrogen (δ¹⁵N) within plants throughout a closed canopy forest, and may facilitate the study of canopy feeding niches in arboreal primates. However, the nuanced relationship between leaf height, sunlight exposure and the resulting variation in isotope ratios and leaf mass per area (LMA) has not been documented for an African rainforest. Here, we present δ¹³C, δ¹⁸O and δ¹⁵N values of leaves (n = 321) systematically collected from 58 primate food plants throughout the canopy (0.3 to 42 m) in Côte d’Ivoire, West Africa. Besides leaf sample height and light availability, we measured leaf nitrogen and carbon content (%N, %C), as well as LMA (n = 214) to address the plants’ vertical resource allocations. We found significant variation in δ¹³C, δ¹⁸O and δ¹⁵N, as well as LMA in response to height in combination with light availability and tree species, with low canopy leaves depleted in ¹³C, ¹⁸O and ¹⁵N and slightly higher in %N compared to higher canopy strata. While this vertical isotopic variation was not well reflected in the δ¹³C and δ¹⁵N of arboreal primates from this forest, it did correspond well to primate δ¹⁸O values.

Dental health is closely linked to an individual’s health and diet. This bioarcheological study presents dental caries and stable isotope data obtained from prehistoric individuals (n = 101) from three Early Neolithic sites (c. 5500-4800 BCE) in central Germany. Dental caries and ante-mortem tooth loss (AMTL) were recorded and related to life history traits such as biological sex and age at death. Further, we correlate evidence on caries to carbon and nitrogen isotope data obtained from 83 individuals to assess the relationship between diet and caries. In 68.3% of the adults, carious lesions were present, with 10.3% of teeth affected. If AMTL is considered, the values increase by about 3%. The prevalence of subadults (18.4%) was significantly lower, with 1.8% carious teeth. The number of carious teeth correlated significantly with age but not sex. The isotopic data indicated an omnivorous terrestrial diet composed of domestic plants and animal derived protein but did not correlate with the prevalence of carious lesions. The combined evidence from caries and isotope analysis suggests a prevalence of starchy foods such as cereals in the diet of these early farmers, which aligns well with observations from other Early Neolithic sites but contrasts to Late Neolithic and Early Bronze Age populations in Germany.

Stable isotope analysis is an increasingly used molecular tool to reconstruct the diet and ecology of elusive primates such as unhabituated chimpanzees. The consumption of C₄plant feeding termites by chimpanzees may partly explain the relatively high carbon isotope values reported for some chimpanzee communities. However, the modest availability of termite isotope data as well as the diversity and cryptic ecology of termites potentially consumed by chimpanzees obscures our ability to assess the plausibility of these termites as a C₄resource. Here we report the carbon and nitrogen isotope values from 79Macrotermestermite samples from six savanna woodland chimpanzee research sites across equatorial Africa. Using mixing models, we estimated the proportion ofMacrotermesC₄plant consumption across savanna woodland sites. Additionally, we tested for isotopic differences between termite colonies in different vegetation types and between the social castes within the same colony in a subset of 47 samples from 12 mounds. We found thatMacrotermescarbon isotope values were indistinguishable from those of C₃plants. Only 5 to 15% ofMacrotermesdiets were comprised of C₄plants across sites, suggesting that they cannot be considered a C₄food resource substantially influencing the isotope signatures of consumers. In theMacrotermessubsample, vegetation type and caste were significantly correlated with termite carbon values, but not with nitrogen isotope values. LargeMacrotermessoldiers, preferentially consumed by chimpanzees, had comparably low carbon isotope values relative to other termite castes. We conclude thatMacrotermesconsumption is unlikely to result in high carbon isotope values in either extant chimpanzees or fossil hominins.