Thu October 13, 2011
In African Cave, An Early Human Paint Shop
Apparently one of the earliest human instincts was to paint things, including bodies and cave walls. That's the conclusion from scientists who have discovered something remarkable in a South African cave — a tool kit for making paint. It looks to be the oldest evidence of paint-making.
Over in southern Africa 100,000 years ago, Homo sapiens was pretty new on the scene. A favorite hangout was a cave named Blombos near the Southern ocean.
Archaeologists like Christopher Henshilwood have spent decades finding stuff there that our ancestors left behind. Recently, Henshilwood uncovered two abalone shells with ocher ground into the shell. "Above and below each shell and to the side of each shell was a complete kit that was used for producing a pigmented mixture," he says.
In addition to the shells were stone flakes, grinding stones and bits of bone with reddish ocher on them. Ocher is a kind of iron oxide dug from the ground that early humans used as a pigment and to thicken glue.
Henshilwood, a professor with the University of the Witwatersrand in South Africa and the University of Bergen in Norway, says his discovery points to decoration.
"I think the most likely explanation for this is that they were producing paint," he says. "This really was the smoking gun."
Henshilwood says for a short time, the cave was a paint shop — the earliest ever seen. The makers added bone and charcoal to a liquid mixture to make it oily and viscous so it would stick. The ocher provided color and a matrix. It was complex chemistry but stirred by hand.
"We can see where the small quartz grains that had adhered to the finger had left a very tiny trace in the shell," Henshilwood says.
In a laboratory at George Washington University, anthropology student Andrew Zipkin opens a bag of ocher and puts it into a mortar, where he grinds it with a pestle.
"You need to sort of tap it and break it up first," he explains. "The finer-grain material here is quite powdery now. This is ready to use. I can mix this with water and I'll have a pretty nice paint out of this."
Zipkin's Ph.D. work focuses on ocher and how to make stuff with it the way ancient humans did.
Lately, he has been exploring the other ancient use for ocher: He's gluing stone points onto arrowheads. Then he tests how well the glue works.
"I went to an Ethiopian butcher in Falls Church, Va., and tracked down a goat carcass they had there," he says. Then he shot the arrows into the carcass. He found that the arrowheads with ocher stayed on better than those without.
Zipkin makes a lot of ocher mixtures — you can tell by looking at his hands and his clothes. He says the recipe has to be followed exactly right, a process that takes planning.
"I think we're going to find that these early people were smarter than we think," says Alison Brooks, an anthropologist at George Washington University. She says working with ocher reflects higher-order thinking, and using it as paint probably represents an early form of symbolic thinking as well.
"The ultimate purpose of putting something on yourself, your house, your walls is to make a statement about who you are," she says. "So it would have been important to identify yourself as a friend."
Whoever these people were — primitive Picassos or house painters — their handiwork lasted 100,000 years, and is described in the journal Science.