We fully agree with the concern of this reviewer about the provenance of the toxins in hair. We had lengthy discussions during the preparation of the manuscript about this particular point. And we stressed, in the discussion of the paper, our inability to exclude the possibility suggested by the reviewer. However, on balance, we were swayed towards our interpretation of the results by the presence of extra cellular polymeric substances we displayed in Figs 4-5. These clearly showed the presence of bacterial activity. We reasoned, and we hope the reviewer will agree, that if the high levels of toxic elements were applied to the hair by human activity in the « 19th and 20th centuries » as suggested, then they should have inhibited the growth of bacteria and removed the extra cellular polymeric substances. Moreover, we found it difficult to account for the lack of putrefaction has evidenced by the preservation of the skin and muscle (shown in Fig. 2) from the putative time of death (the end of 15th century) to the 19th century.
The interventions proposed by the reviewer although clearly reasonable, occurred some three centuries after death. We were faced with the difficulty of explaining why in this particular specimen tissue preservation was so exquisite, unlike what is generally expected, after centuries without preservatives. We, therefore, opted for the idea that it was bacterial activity that accounted for the unusual preservation of this specimen; an idea that only recently was found to have merit [see: Reith F, Rogers SL, McPhail DC, Webb D. (2006). Biomineralization of gold : Biofilms on Bacterioform Gold. Science Vol. 313: 233-236, as quoted].
We took stable isotope ratios to be good indicators of « paleonutrition » following the example given in reference:
Macko SA, Engel MH, Andrusevich V, Lubec G, O’Connell TC, Hedges REM (1999). Documenting the diet in ancient human populations through stable isotope analysis of hair. Philosophical Transactions of the Royal Society of London B Biological Science. 354 (1379): 65-75 as quoted in reference 12 of our paper.
We do not claim expertise in this area and apologize if we misinterpreted the above reference; a distinct possibility. We would like to emphasize, however, that our contribution was intended merely as an alert to the likelihood of bacterial activity, after death, accounting for the results of elemental analysis of hair, something that hitherto as been taken to reflect solely pre-mortem metabolism and not post-mortem bacterial activity.
Oxford Radiocarbon Accelerator Unit measured the stable isotopes values in hair. In their opinion, the d13C and d15 N values suggest either a small but significant C4 component in a predominantly C3 diet, or a minor marine protein component.
Regarding the anthropological and historical information, the Museum policy precludes us to identify the actual source of this specimen's acquisition but for its definitive South American origin.