Response to Thackeray (2016) – The possibility of lichen growth on bones of Homo naledi: Were they exposed to light?

Abstract

[Extract] Thackeray questions the hypothesis of deliberate body disposal in the Rising Star Cave by Homo naledi, as proposed by Dirks and colleagues. Thackeray proposes that lichens produced mineral staining on the skeletal remains of H. naledi. As lichens require some exposure to light, in Thackeray's opinion, the presence of mineral staining necessitates either a direct entrance deep into the Rising Star Cave that once admitted light into the Dinaledi Chamber, or relocation of mineral-stained bones from a location exposed to light. Here we consider multiple lines of evidence that reject Thackeray's hypothesis that lichens deposited mineral staining upon the surface of these skeletal remains. We welcome the opportunity to address the inferences presented by Thackeray, and further hope that this response may dispel misinterpretations of our research, and of other areas of the scientific literature that bear upon site formation processes at work within the Rising Star Cave system.