Archaeologists excavating a cave on the coast of South Africa not long ago unearthed an unusual abalone shell. Inside was a rusty red substance. After analyzing the mixture and nearby stone grinding tools, the researchers realized they had found the world’s earliest known paint, made 100,000 years ago from charcoal, crushed animal bones, iron-rich rock and an unknown liquid. The abalone shell was a storage container—a prehistoric paint can.
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The find revealed more than just the fact that people used paints so long ago. It provided a peek into the minds of early humans. Combining materials to create a product that doesn’t resemble the original ingredients and saving the concoction for later suggests people at the time were capable of abstract thinking, innovation and planning for the future.
These are among the mental abilities that many anthropologists say distinguished humans, Homo sapiens, from other hominids. Yet researchers have no agreed-upon definition of exactly what makes human cognition so special.
“It’s hard enough to tell what the cognitive abilities are of somebody who’s standing in front of you,” says Alison Brooks, an archaeologist at George Washington University and the Smithsonian Institution in Washington, D.C. “So it’s really hard to tell for someone who’s been dead for half a million years or a quarter million years.”
Since archaeologists can’t administer psychological tests to early humans, they have to examine artifacts left behind. When new technologies or ways of living appear in the archaeological record, anthropologists try to determine what sort of novel thinking was required to fashion a spear, say, or mix paint or collect shellfish. The past decade has been particularly fruitful for finding such evidence. And archaeologists are now piecing together the patterns of behavior recorded in the archaeological record of the past 200,000 years to reconstruct the trajectory of how and when humans started to think and act like modern people.
There was a time when they thought they had it all figured out. In the 1970s, the consensus was simple: Modern cognition evolved in Europe 40,000 years ago. That’s when cave art, jewelry and sculpted figurines all seemed to appear for the first time. The art was a sign that humans could use symbols to represent their world and themselves, archaeologists reasoned, and therefore probably had language, too. Neanderthals living nearby didn’t appear to make art, and thus symbolic thinking and language formed the dividing line between the two species’ mental abilities. (Today, archaeologists debate whether, and to what degree, Neanderthals were symbolic beings.)
One problem with this analysis was that the earliest fossils of modern humans came from Africa and dated to as many as 200,000 years ago—roughly 150,000 years before people were depicting bison and horses on cave walls in Spain. Richard Klein, a paleoanthropologist at Stanford University, suggested that a genetic mutation occurred 40,000 years ago and caused an abrupt revolution in the way people thought and behaved.
In the decades following, however, archaeologists working in Africa brought down the notion that there was a lag between when the human body evolved and when modern thinking emerged. “As researchers began to more intensely investigate regions outside of Europe, the evidence of symbolic behavior got older and older,” says archaeologist April Nowell of the University of Victoria in Canada.
For instance, artifacts recovered over the past decade in South Africa— such as pigments made from red ochre, perforated shell beads and ostrich shells engraved with geometric designs—have pushed back the origins of symbolic thinking to more than 70,000 years ago, and in some cases, to as early as 164,000 years ago. Now many anthropologists agree that modern cognition was probably in place when Homo sapiens emerged.
“It always made sense that the origins of modern human behavior, the full assembly of modern uniqueness, had to occur at the origin point of the lineage,” says Curtis Marean, a paleoanthropologist at Arizona State University in Tempe.