Figure 4: Extent of isoleucine epimerization in Genyornis eggshell compared to their current regional temperatures.

Average A/I in Genyornis eggshell from 63 collections with burnt fragments recovered from all ten regions (Fig. 1) for which a secure A/I could be determined, plotted against their current (1960-1990 AD) mean annual temperature (MAT), each with its ±1σ uncertainty (Supplementary Data 2). Letters refer to regions in Fig. 1, numbers in parenthesis are the number of collections from each region, and the number of different eggshell fragments analysed in each region that contribute to the mean A/I value. The close fit to a simple polynomial regression with a trend towards ever-higher A/I for higher regional MATs, an expected result due to the exponential dependency of racemization rate on temperature, is consistent with, although not in itself proof of, all samples being of the same age. Age differences in excess of 5 ka in almost all cases would result in a significantly poorer polynomial fit.