Identifying Asteraceae, particularly Tarchonanthus parvicapitulatus, in archaeological charcoal from the Middle Stone Age

Abstract

Sibudu rockshelter, an archaeological site in KwaZulu-Natal, has evidence of the local vegetation, environment and wood use during the Middle Stone Age, from well-preserved seeds and charcoal, approximately 77–38 000 years ago. In order to confidently identify some charcoal taxa, closely related species were studied in detail. Modern wood was charred and examined under the light microscope and a combination of anatomical features was used to distinguish the various taxa. Tarchonanthus parvicapitulatus P.P.J. Herman (syn. in part Tarchonanthus camphoratus L.) is an evergreen, woodland shrub or tree, which is tolerant of hot, dry, salty or icy conditions. Essential oils from the leaves have antimicrobial and insecticidal properties. The camphor smoke is used in traditional African medicine, the aromatic leaves are used in organic camp bedding and the hard, heavy wood is insect resistant. Since the wood anatomy of this shrub is very similar to Brachylaena discolor DC, another woody member of the Asteraceae, the modern reference charcoal has been studied, to distinguish between these and other species. The confirmed presence of aromatic T. parvicapitulatus in hearths probably implies deliberate burning for insect repellent smoke.