Anatomically modern human beings (homo sapiens) first emerged in northeastern Africa about 150,000 to 200,000 years ago. However, the critical difference between humans and our primate relatives is more than just anatomy: humans exhibit symbolic thought (which includes language). Did symbolic thought emerge with modern anatomy, or did it occur at a later time?
Symbolic thought involves the ability to identify and create representations of things. This might be in terms of sounds (spoken language), signs (sign language), or art. Since it is difficult to find evidence of words in the archaeological record, archaeologists have generally relied upon art as evidence of symbolic thought. Based on the discovery of the paintings in Lascaux Caves and other sites in Europe, some paleontologists have suggested that there was a creative explosion about 50,000 years ago that provides evidence of a blossoming of symbolic thought. Data from Africa, however, suggests that homo sapiens may have had symbolic thought much earlier than this.
Blombos Cave in South Africa provides some of the earliest evidence of the human capacity for symbolic thought. Archaeologists generally feel that symbolism, an important aspect of human cognition that is closely associated with language, is indicated by visual art, personal decorations (both body decoration such as painting and jewelry), and ritual behavior (often seen in burials). The evidence from Blombos Cave shows this type of human behavior by about 75,000 to 100,000 years ago.
Blombos Cave is located in a calcarenite limestone cliff on the Southern Cape coast. At the present time it is located about 100 meters (330 feet) from the coast and about 35 meters (115 feet) above sea level. Humans were using this cave by 140,000 years ago. It was used as a fishing and shellfishing site. Faunal remains found at the site reveal thousands of fish bones, as well as seals, dolphins, and terrestrial animals.
By 78,000 years ago the people at Blombos Cave were using a variety of bone tools in addition to stone tools.
Humans there were using red ochre (an iron ore used world-wide as a pigment). Tens of thousands of pieces of red ochre have been found at the site. According to K. Kris Hirst:
Ochre has no known economic function; it is almost universally accepted as a source of color for ceremonial, decorative purposes. The Blombos Cave layers containing used ochre are dated 70,000 to 80,000 years before the present.Two of the ochre slabs are marked with incised lines. Small pieces of ochre were first scraped and ground to create a flat surface. Then a complex array of lines was carved into the prepared surface. Some of the researchers have interpreted this as an early form of art and cite it as evidence of the early human capacity to think abstractly using symbols. Sean Henahan reports:
These findings suggest that early Homo sapiens were able to think abstractly, behaving like modern humans much earlier than was previously believed possible.
A recent discovery at the cave included two art toolkits which date to about 100,000 years ago. These kits include two abalone shells containing an ochre-rich mixture. Associated with these artifacts were bone, charcoal, grindstones, and hammerstones. Pieces of ochre would have been rubbed on the quartzite grindstones to produce a fine red powder. The ochre would be combined with heated, crushed mammal bone, charcoal, stone chips and a liquid which would then be gently stirred in the abalone shells. Dating of these tool kits was done with Optically Stimulated Luminescence (OSL) of the quartz sediments in which they were found. According to Christopher Henshilwood:
“The recovery of these toolkits adds evidence for early technological and behavioral developments associated with humans, and documents their deliberate planning, production, and curation of pigmented compound and the use of containers. It also demonstrates that humans had an elementary knowledge of chemistry and the ability for long-term planning 100,000 years ago.”Some people feel that the geometric quality of the art hints at the development of symbolic language. According to Christopher Henshilwood:
"They may have been constructed with symbolic intent, the meaning of which is now unknown. These finds demonstrate that ochre use in the Middle Stone Age was not exclusively utilitarian and, arguably, the transmission and sharing of the meaning of the engravings relied on fully syntactical language."In addition to the red ochre, the excavations at Blombos Cave have also uncovered many shells which have been deliberately perforated. The shells, which are from a tiny species of mollusk that lived in a nearby estuary, carry traces of red ochre and show signs of wear. They suggest that the humans at this site were using them as beads, another indication of abstract thinking.
Of the 60 beads uncovered at Blombos Cave, 27 seem to have been a part of a single garment. In other words, they were decorations and may be interpreted as an indication of abstract thought.
Art and decorations are not the only indications of abstract thought that archaeologists look for. Tool making which requires complex steps with different materials. This type of tool making indicates planning, an ability to think about the future. By 75,000 years ago, the people at Blombos Cave were making and using a distinctive type of stone points (most likely used as spear points). These were made using a pressure-flaking method, assisted by heat treatment, similar to that used in making the Salutrean toolkit in Europe about 20,000 years ago.
Pressure flaking allows a finer, more precise cutting edge to be created in stone tools. Archaeologists generally consider pressure flaking to be an advanced form of flintknapping. Pressure flaking often involves the use of a bone or antler tool to apply pressure on the area where a small flake is to be removed.
Heat treatment involved the controlled use of fire on raw lithic material to improve its flaking quality. Heating that raw material to between 300-450 degrees centigrade (a wood or charcoal fire does that) changes the stone, allowing the resulting fractures to follow the natural grain of the stone, rather than across the grain. The stones to be worked would be placed in the fire for just a few minutes to make them more amenable to pressure flaking. Heating also changes the stone’s color and increases its luster.