SCIENCE -- October 13, 2011 at 2:12 PM EDT
Ancient Paint Studio Unearthed
The abalone shell before excavation from the 100,000 year old, Middle Stone Age-levels at the Blombos Cave in South Africa. Photo by Science/AAAS.
Researchers have unearthed two abalone shells from a South African cave that they believe were used to produce and store a mixture of pigmented paint, and that possibly represent the first known use of containers. The discovery, released in the journal Science on Thursday, also indicates that as long as 100,000 years ago, humans had strategic planning skills and knew some basic chemistry.
Excavated from the Blombos cave near the southern Cape shore of the Indian Ocean in South Africa, the finding consists of two "toolkits" found side by side, containing fragments of ancient grinding, crushing and painting tools, along with the shells. All had residue of ochre, earth pigment derived from iron oxides and other natural minerals, which has been well-documented as a source of early colored paint.
The recovery should be seen as evidence that homo sapiens were deliberately producing and curating a pigmented compound, said Christopher Henshilwood of the University of Witwatersrand, Johannesburg, and the paper's lead author. "Homo sapiens thus had an elementary knowledge of chemistry and the ability for long-term planning," he added.
The artifacts were found deep in aeolian dune sand, and the best preserved item is a very large abalone shell, containing dry residue of the red pigment, said Francesco d'Errico, an anthropologist at University of Bordeaux and an author of the study.
Microscopic analysis of the residue showed that the paint was made of ochre powder, fatty crushed bone believed to act as a binder, charcoal, quartz grains and an unknown liquid. A 6 centimer-long spatula was used to transfer small quantities of liquid out of one abalone container and may also have been used as a paintbrush or palette knife for painting.
The paint could have been used for skin decoration or cave painting, but its use is unclear.
"In fact, it's quite paradoxical," d'Errico said. "We know very well how the pigment was produced, but very little about on what it was put."
Details suggest that the mixture used was sophisticated and well-tested. Researchers believe that pieces of ochre were rubbed on slabs of quartzite rock to produce a fine powder and then crushed with grinders. Mammal bone was possibly heated before crushing to help extract marrow fat that would have served as a sort of glue. Then hematite powder, charcoal, crushed trabecular bone, stone chips, quartz grain and liquid were added and gently stirred.
Lyn Wadley, an archaeology professor at the University of the Witwatersrand who was not involved in the study, said that the compounds produced yield more information about humans 100,000 years ago than the ochre-processing toolkits themselves. "The creation of compounds...implies that people of the time had complex cognition. By this I mean, they could, for example, multi-task and think in abstract terms about the qualities and necessary quantities of the ingredients that they manipulated. Making compounds of any kind implies complex cognition, and we can come to this conclusion without knowing what the compounds were used for."
A study published by the same team in the Journal of Human Evolution in 2009 found that ochre was also being engraved with various designs at Blombos during the same time period.
Scientists used optically stimulated luminescence (OSL) dating of the quartz sediments to date the toolkits at about 100,000 years old.
The most surprising aspect of the discovery for d'Errico was an egg shape in the abalone shell indicating the movement of a person's finger. "I have a fossilized motion of somebody who was mixing the pigment 100,000 years ago - the oldest motion of an artisan producing a pigment," he said.
Interior view of the Blombos Cave. Photo by Magnus Haaland.