Diggings and important findings in the Blombos Cave

20 May 2012

Speaker:    Petro Keene

A South African archaeologist with a considerable international reputation, Professor Christopher Henshilwood discovered Still Bay's important prehistoric cave site in 1991.  He has close ties with two leading Universities – Wits in Johanneburg and Bergen in Norway. 

Systematic analysis at what is now known as the Blombos Cave began in 1992. And the site was excavated between 1997 and 2011, following  deployment of a team of excavators and after additional on-site investigation by archaeologist Cedric Poggenpoel.  

It remains under Henshilwood's overall direction. And more excavation work is in the pipeline. 

When this activity began, the cave entrance had been almost totally sealed by dune sand. It is a small cave, leading off a smaller ante-chamber that has only recently been discovered.  

Excavation activity to date has revealed a cave interior of 55 square metres of visible deposits, with estimated depths of about 4,5 metres at the front end and some 3 metres toward the rear. 

Archaeological  activity so far has also uncovered Middle Stone-Age layers providing evidence of  human habitation – along with fishing activity – conceivably going back

110 000 years. And so-called Later Stone-Age occupation – from roughly 2000 years ago until as recently as perhaps 290 years ago. 

(There appears to have been no human or animal activity to disturb the cave's contents since about 1720 AD – 66 years after van Riebeeck – hence not for the past 290 years.) 

Middle Stone Age occupation:  here the surrounding mass or matrix is mainly dune sand blown in through the cave entrance, along with sea-shells, decomposed materials, limestone  and wind-borne halites (rock-salt).  Another feature of these deposits is that they undulate considerably from the back to the front of the cave, due to subsidence that has produced a 'wrapping effect'  by subsequent rock falls.  

The deepest and earliest Middle Stone Age period, going back 100 000 years – and which is referred to as the 'upper M3 phase' – is characterised by shellfish deposits and a high incidence of ochre pieces (indicating that  it did not conform to the 'typical' Middle Stone Age pattern previously observed at Klasies River). 

Finds that have been identified as finely-made scrapers  (some circular, others appearing to be end-scrapers)  also suggest that hide preparation– whether for 'home comforts' or crude apparel – also took place at the site in that earliest period. 

The so-called M2 phase comprises no fewer than four levels of carbonised deposits; large hearths; and shellfish.  Shaped bone tools 'possibly used as awls and projectile points'  came mainly from M2 layers, but also from the M1 phase – comprising the five uppermost layers of Middle Stone Age  occupation – that came later. 

The 'stratigraphic integrity' of artifacts recovered from these levels has been demonstrated,  which is to say that there is minimal evidence of movement of artifacts as between the Middle Stone Age phases. 

Later Stone Age occupation: these deposits are more massively bedded; and, being less than 2000 years old are relatively undistorted. In addition to that, burned layers tend to be thicker and several of these appear to preserve (reflect) their original hearth-like structures. 

Carbonised deposits reflect occupation boundaries: hence separate major occupying groups. However these  deposits undulate considerably from the back to the front of the cave, due to subsequent subsidence that produced a 'wrapping' effect over the rock falls. 

In this period ground waters rich in calcium carbonate percolated through the cave roof and walls, creating an environment helpful to preservation of bone and shell – particularly near to what have been identified as hearths and ash deposits. 

Burned layers tend to be thicker, with several appearing to preserve their original hearth-like structures. 

More recent dating: During the 2008 excavation Dr Chantal Tribolo selected 24 lithics (stone items) for thermoluminescence dating;  while Professor Stein-Erik Lauritzen selected five sample flowstones for uranium-thorium dating in Norway. 

Human material recovered from the Middle Stone Age finds is small - just nine teeth.  The crown diameters of some of these suggest the then Blombos residents were 'probably anatomically modern'; findings supported by similar evidence from nearby Klasies River. 

Genetic and fossil evidence suggests that humans were 'anatomically near-modern' more than 100 000 years ago. A key question is whether 'anatomical and behavioral modernity' developed in tandem.  In this respect there is agreement on one criterion; namely that evidence of 'abstract or depiction images' (primitive art) indicates modern human behaviour; and – here quoting Professor Henshilwood – that  no clear distinction can be made between Middle Stone Age and Later Stone Age subsistence behavior at Blombos  Cave. Moreover, an impression that the Blombos Cave engravings are 'intentional images' – in the light of which it seems that, in southern Africa at any rate, Homo Sapiens was  behaviorally modern some 77 000 years ago. 

More than 30 bone artifacts have been recovered at Blombos Cave. Bone tools are taken as providing comprehensive evidence of systematic bone tool manufacture and use. 

Microscopic analysis of a bone fragment marked with eight parallel lines indicates that these are the result of deliberate engraving and were 'possibly made with symbolic intent'. 

The discovery of more than 65 shell beads in Blombos Cave 'has added a new dimension to modern human behavior debates'. 

Animal remains collected from Blombos Cave show that Middle Stone Age people practiced a 'subsistence strategy' that included a very broad range of animals, large and small (from eland to tortoises and dune mole rats).  They also brought seal, dolphin and probably whale meat back to the cave. More than 1200 fish bones have been recovered from the Middle Stone Age debris. Blombos Cave shellfish remains provide early evidence of their popularity as sea-foods possibly going back 110 000 years. 

Excavations at Blombos Cave in 2008 revealed a 'processing workshop' where a liquefied ochre-rich mixture was produced and stored in in two Haliosis Midae shells 100 000 years ago. 

All this represents an outstanding example of a traditional human settlement, land-use or sea-use, which is representative of a culture, or at least of human interaction with the environment.

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