Ochre use at Sibudu Cave and its link to complex cognition in the Middle Stone Age

[摘要] Ochre is found at many Middle Stone Age (MSA) sites and its use is often attributedby archaeologists to enhanced mental abilities and symbolism. However, the linksbetween the visible uses of ochre, cognition and symbolism have not been clearlydemonstrated. Here it is argued that by understanding ochre processing technology andsome of the stages involved in using ochre, one can determine the skill, knowledge andcognitive abilities required to execute those activities. In order to understand the usetracesfound on ochre, and to enable the identification of them, as well as the types ofochre used, experiments were first performed with geological ochre specimens. Ochrepieces collected from the Sibudu surrounds were used experimentally for a variety ofgrinding, scoring and rubbing activities. All use-traces created on the ochre piece duringan activity were macro- and microscopically examined, recorded and compared.Experimental ochre pieces ground against a coarse or fine-grained slab developparallel striations. Grinding results in significant changes to the surface shape of theochre, and often results in faceted edges. Scoring can be performed with the intention tocreate powder, or to create a design. The incisions created from scoring often do notreach all the edges of the used surface and they regularly have frayed terminations. Afrayed incision termination shows that the incision was created by multiple scoringstrokes. When ochre is scored to manufacture powder the incisions that are generatedare parallel groups of grooves with erratically oriented grooves as well. Grooves createdthrough both grinding and scoring have microstriations within them and they show arange of profile shapes. The most common use-wear from rubbing ochre on softmaterials is smoothing, edge rounding and polish. Microstriations and metallic lustreoccasionally form during rubbing. The collection of utilised experimental ochre formed acomparative collection for the examination of the Sibudu ochre.The main body of this research comprises a study of the Middle Stone Age ochreassemblage from Sibudu, KwaZulu-Natal, South Africa. Sibudu has a large Middle StoneAge ochre assemblage of over 9000 pieces of ochre from layers dating between ~77 kaand ~37.6 ka. All pieces were examined to determine the types of ochre used and toinspect all use-traces present on the pieces. The assemblage comprises 5449 ochre piecesiv>8 mm, including 682 pieces with markings from use. The pre-Still Bay (~77 ka) andHowiesons Poort (~65–62 ka) layers have the highest percentage of utilised pieces.Bright-red ochre was preferentially selected for use throughout most of sequence. Thereis evidence of the preferential selection of specific types of ochre for use in the Sibuduassemblage. Shale and pieces with medium hardness values are common throughout thesequence. Grain sizes change through time – pieces with clayey grain sizes are favouredduring the Still Bay and Howiesons Poort, whereas silty grain sizes are preferred in theyounger Middle Stone Age occupations. High frequencies of bright-red amongst theutilised pieces, coupled with high frequencies of yellow or orange pieces with noevidence of use, suggest that colour choices were deliberate and not a product of postdepositionalheating. Chemical analysis of a sample of utilised pieces indicates that theyall contain iron, silicon, aluminium and calcium; many pieces contain hematite and somecontain maghemite.Use-traces were divided into activity categories, based on experimental results.Combined grinding and rubbing is the most frequent activity for which ochre pieceswere used. Grinding and rubbing use-wear also occurs independently on many pieces.Scored pieces are rare, but are more frequent in the pre-Still Bay (~77 ka) industry thanelsewhere in the sequence. Some of the incisions appear to be deliberate engravings, andparallel lines and fan-like marks are the most often repeated patterns. Use-tracesacquired during powder-producing activities predominate, implying a desire to createochre powder. Powder-producing activities were mainly performed with bright-redpieces, while minimal scoring is mainly present on brown-red pieces. Pieces with micainclusions are not common, but were frequently used for powder-producing activities.Once the activities performed with ochre were established, thought-and-actionsequences, or cognigrams, were constructed. This helped establish the steps involved ineach activity and the temporal and physical distance between the commencement of atask to its completion. Inferential sequences were constructed to establish theprocedures and knowledge needed to complete an activity, thereby establishing thecognitive prerequisites. Cognitive interpretations are made using the concept ofenhanced executive functions of the brain. The construction of the inferential thoughtvand-action sequences showed that the various ways that ochre was used have differentcognitive requirements.Powder-production alone is not an indicator of complex cognitive processes,although some planning, foresight and knowledge of materials is required. Some of thepowder was used in the creation of hafting adhesives, which is a cognitively demandingprocess requiring attention-switching ability, response inhibition and abstract thought.Grinding ochre and then rubbing the piece on a soft material for the direct transfer ofpowder does require some complex mental abilities, such as multi-tasking and switchingattention. Scoring a piece of ochre with a sharp tool does not necessitate enhancedexecutive functions, but some engravings demonstrate foresight, intentionality and anawareness of space and symmetry that may demonstrate abstract thought.This research provides a complete description of the Middle Stone Age ochreassemblage at Sibudu, and establishes the way that ochre was used at the site. Thiscontributes to the debate on the advent of enhanced behaviours in the past by providinginsight into the cognitive abilities required by the ochre users. It offers a method ofanalysing ochre use in the past by drawing on cognitive theory and the visibleapplications of ochre. Both simple and complex cognitive abilities were required forochre activities at Sibudu. The requirement for cognitively complex abilities in some ofthe ochre-related activities at Sibudu suggests that the people living there during theMSA had advanced mental capabilities like modern humans living today. This researchshows how ochre use can be employed as a proxy for cognitive capabilities, and cantherefore shed light on the evolution of the modern mind.

[发布机构] University of the Witwatersrand