Seeds from the Middle Stone Age layers at Sibudu Cave

Carbonized seeds, nuts and the stones of fruits are present in Middle Stone Age (MSA) layers at Sibudu Cave from more than ~60 ka ago to about ~37 ka ago. In spite of the preservation of at least 66 taxa, the lack of comparative material allowed for the identification of only 35 taxa to family, genus or species. The remaining taxa were assigned Type numbers. The identified taxa consist of sedges, grass and woody climbers, shrubs and trees that are mostly present in the evergreen forest, forest margins and riverine vegetation in the shelter environs, or occur in similar habitats nearby. The sedges indicate the presence of open water, probably in the Tongati River, and they may have been harvested by people throughout the MSA sequence. Because of the widespread distribution and the wide range of environmental tolerances of many of the identified woody plants, various likely interpretations about vegetation change are possible and the taxa on their own provide inconclusive evidence of vegetation change during the MSA occupations at Sibudu. Frequency distributions of evergreen and deciduous taxa were compared through time. Taxa identified by charcoal analyses were combined with seed data to increase the sample size and provide more comprehensive representation of the prevailing vegetation. When the taxa are grouped according to age clusters, evergreen woody taxa appear to predominate at about 60 ka, followed by a marked increase in deciduous taxa. This trend may alter when larger reference collections allow for identification of more of the unidentified seed and charcoal taxa. The increase in deciduous taxa occurs at a time of gradual warming indicated by magnetic susceptibility studies, but it is unclear exactly how the increase relates to moisture availability and temperature. The trend may be interpreted as an indication of a greater deciduous element in the forest, or of more open vegetation near Sibudu Cave around ~50 ka ago than was previously the case.