Degree Name

Bachelor of Science (Honours)


0403 GEOLOGY, 040303 Geochronology


School of Earth & Environmental Sciences


Zenobia Jacobs


Behavioural modernity, however defined, is considered to be the key distinctive feature separating Homo sapiens from earlier hominid lineages. While the fossil and genetic records imply that modern human morphology evolved in Africa between 250 and 150 thousand years (ka) ago, there is currently no unification regarding the timing or geographical origins of modern human behaviour (MHB). An increasing body of evidence suggests modern behaviour was present during the African Middle Stone Age (MSA). Defining the origins of MHB requires accurate and precise chronologies of when they first emerged.

Blombos Cave in South Africa has yielded a collection of well-preserved cultural material from within the MSA layers. These include bone tools, shell beads, engraved ochre slabs and an assemblage of stone artefacts which are believed to represent a dynamic tool industry, the Still Bay (SB). More recently, ochre containers which may contain evidence for the ingredients used to produce paint, have been found in the lower layers of the cave, along with a tool kit, such as bone spatulas, that suggest an even earlier origin of MHB. The likely symbolic significance of these artefacts implies cognitive sophistication of MSA hominids and modern human behaviour previously only asserted in LSA people.

Examination of both sediments and anthropogenic deposits within the MSA levels have allowed the MSA layers of Blombos Cave to be subdivided into separate phases and layers. Each of these has been systematically dated in this study using optically stimulated luminescence (OSL) dating techniques. The improved temporal resolution of this site contributes to the debates regarding the key mechanisms behind the emergence of MHB. Two leading theories regarding the emergence of MHB include: 1) environmental change, and 2) demographic change.

OSL ages of sediments associated with these MSA levels suggest the SB industry occurred between 70 and 80 ka ago, with the other symbolic behaviours being recognised at ~110 ka. Such ages imply that MHB was present in southern Africa during the MSA and that it occurred sporadically, possibly as an outcome of increased human population and environmental conditions that were happening concurrently.