Fig 1.
Indian Ocean slave trading routes.
Map generated based on images provided by Iziko Museums and Frans Huijzenveld (Faculty of Humanities, department of Art and Culture, History, and Antiquity, Vrije Universiteit Amsterdam).
Fig 2.
Schematic geological map of the southwestern Cape.
Figure adapted from Compton et al. [70]. Strontium isotope data as published by Sealy et al. [69] and Balasse et al. [68].
Table 1.
Osteological data and selected teeth for strontium isotope analysis from 35 individuals from the Cobern Street informal burial site, Cape Town, dating to the colonial period.
Table 2.
Chronology of human dentition in South African populations.
Average crown formation times from [49].
Table 3.
Osteological, carbon, nitrogen, and strontium isotope data from 35 individuals from the Cobern Street informal burial site, Cape Town, dating to the colonial period.
Table 4.
Statistical assessment of human 87Sr/86Sr data (this study) and δ13C [21] data from Cobern Street, Cape Town.
Fig 3.
Tukey’s schematic boxplot showing 87Sr/86Sr variation for the background data (n = 18: Sealy et al. [69] and Balasse et al. [68]), the (trimmed) Cobern Street data (this study), and the variation in δ13C for the dentine (n = 36) and cancellous bone (n = 50) samples from Cox et al. [21].
Key: the boxes represent the interquartile range (IQR: Q3-Q1), the central line indicates the median. The whiskers represent Q1–1.5*IQR and Q3 + 1.5*IQR. The circles represent mild outliers (>1.5*IQR), the asterisks extreme outliers (>3*IQR). The trimmed dataset resembles a normally distributed dataset in which the statistical outliers are excluded.
Fig 4.
Strontium isotope data from M1 and deciduous teeth data from 33 individuals. The horizontal lines mark the local strontium range.
Key: “+” next to sample number indicates the presence of intentional dental modifications. Open symbols identify individuals who exhibit non-local δ13Cdentine values. The standard errors in the analytical data are smaller than the plotted symbols.
Fig 5.
Multi-dental elemental strontium isotope data from 17 individuals. The horizontal lines mark the local strontium range.
Key: “+” next to sample number indicates the presence of intentional dental modifications. Open symbols identify individuals who exhibit non-local δ13Cdentine values. The standard errors in the analytical data are smaller than the plotted symbols.