What excavated beads tell us about the when and where of human evolution

A panoramic view of the interior of the Blombos Cave, which holds fascinating insights into human evolution. Supplied

The origins of “modern human behaviour” generate lively debate worldwide. The central question in these discussions is:

When and where did our common ancestors first start behaving in ways similar to ourselves?

Although it is well known that Homo sapiens were anatomically modern by 200 000 years ago in Africa, evidence to support the idea that the “behavioural modernity” of Homo sapiens originated in Africa had long remained elusive. That was until the discovery of the Blombos beads on 24 April 2004. Twelve years later, new discoveries relating to early Homo sapiens cognitive abilities are still challenging mainstream views.

A central achievement and focus of our (now many) publications is recognising that the most ancient symbolic traditions in Africa date back at least 100 000 years. The widely recognised impact of our scientific activities has firmly placed archaeology in South Africa as among the world leaders in the field of modern human origins research. This will continue with the discovery of new sites and new excavations.

Blombos Cave, an archaeological site situated on South Africa’s southern Cape coastline, contains Middle Stone Age archaeological deposits (hearths, bone, stone, marine shells and sand in discrete layers) dated at between 100 000 and 72 000 years ago. This is probably the most important period in the early development of modern human behaviour. Published results from Blombos Cave suggest that some aspects of “modern behaviour” evolved during the early Late Pleistocene (after 100 000 years) in Africa. Excavations at the cave complement recent and older findings from a number of African Middle Stone Age sites that date to this time period.

The findings from Blombos Cave and subsequent re-analysis and excavation of other sites have resulted in a paradigm shift in our understanding of the timing and location of the development of modern human behaviour. These discoveries clearly reflect the acquisition of fully modern cognitive abilities by southern African populations at least 100 000 years ago.

What constitutes modern human behaviour

Modern human behaviour can be defined as behaviour that is brought about by socially constructed patterns of symbolic thinking, actions and communication. This allows for material and information exchange and cultural continuity between and across generations and contemporaneous communities. The capacity for symbolic thought is not the key defining factor for modern human behaviour. It is rather the use of symbolism to organise behaviour that defines us.

In other words, early humans were first behaviourally modern when symbols became an intrinsic part of their daily lives.

A symbol can be explained as a sign that has no natural or resembling connection to the thing it refers to, only a conventional one. The most common use of the term symbol is for signs that are not words, for example a bald eagle that stands for the United States of America.

Symbols cannot exist in isolation, but generally form a part of interlinked systems.

Examples of symbol use by early Homo sapiens include the use of syntactic (complex) language and the production of material culture that carried symbolic meaning. The production of things that carry meaning is frequently referred to as “symbolic material culture”. Examples include the first jewellery and abstract engravings.

A symbolically mediated culture is one in which individuals understand that artefacts are imbued with meaning and that these meanings are construed by and dependent on collectively shared beliefs. This criterion is crucial. It explains how human norms and conventions differ from the ritualised behaviours found in nonhuman primates.

In simple terms this means that people were able to use the artefacts that they made to organise (mediate) their social world in much the same way as we do today. Within each group of people artefacts may have had meanings that were understood only within that group. An example is the design of a bead necklace which may have carried a specific meaning that was not understood by people who were not a part of that group.

This is not dissimilar to how material culture now identifies people who belong to a specific group. Wearing a cross, for example, identifies you as a Christian believer.

Personal ornaments as symbols in prehistory

A strong argument for early behavioural modernity in the Upper Palaeolithic of Europe after 40 000 years ago is the presence of personal ornaments. The discovery of more than 65 Nassarius kraussianus (‘tick shell’) beads in the 75 000 year old Still Bay phases at Blombos Cave has added a new dimension to the modern human behaviour debates.

Since 1992 each excavation season at the site has yielded important new information on the behavioural evolution of Homo sapiens. This includes, dated at 75 000 years ago, among the earliest known evidence for the manufacture of personal ornaments. Some of the major discoveries are:

  • shell beads,

  • formal bone tool production,

  • the first known engraving of abstract designs on ochre and bone,

  • evidence of the deliberate heating of silcrete, a lithic raw material,

  • and the subsequent manufacture of bifacial stone points on this material using pressure flaking, 50 000 years before this technology was first used in Europe during the Solutrean period about 20 000 years ago.

In the 100 000 year levels a complex tool kit was uncovered. This provides the oldest known evidence for the use of containers and for the production of an ochre rich pigment or paint.

All the recovered ‘tick’ shells from Blombos Cave were carefully pierced 75 000 years ago using a bone tool to create a keyhole perforation. These were then strung, perhaps on cord or sinew and worn as a personal ornament. Repeated rubbing of the beads against one another and against the cord resulted in discrete use-wear facets on each bead. These are not on the shells in their natural environment. The use-wear patterns are the principal factor that defines the shells as beads. Microscopic residues of ochre occur inside some of the beads and result from deliberate colouring or by transfer when worn.

The shell beads also provide insights into technological aspects including the ability to drill, the use of cord or gut for threading and the probable tying of knots to secure the beads.

A comprehension of self-awareness or self-recognition is implied by the wearing of beads or other personal ornaments and was likely an important factor in cognitive evolution that was selected for long before the introduction of beads.

As also suggested by the engraved ochre pieces, complex language would have been essential for the sharing of the symbolic meaning of personal ornaments within and between groups, as well as over generations.