Fig. 2: Regression of paired δ15Nenamel versus δ15Nbone-collagen values (\(\bar{x}\) ± 1σ) for all modern African mammals (n = 33).

The dashed line represents a hypothetical 1:1 relationship between bone collagen and enamel values. The solid line indicates the regression, with a bootstrapped 95% confidence interval illustrated with gray shading. The equation for the regression, R2 value, and p value are indicated in the lower right of the figure. δ15Nenamel versus δ15Ndentin-collagen values for the four fossil Tam Hay Marklot (THM) specimens (see Table 2) are also plotted for reference (black diamonds) but were not included in the regression calculation.