Thinking in Symbols

Modern human culture underwent a "creative explosion" in Ice Age Europe 40,000 to 10,000 years ago. The evidence, which ranges from fantastic cave paintings to elaborate graves to innovative tools, is a sure sign that human symbolic thought–our ability to create and combine meaningful symbols to represent the world–was in full bloom. What evolutionary steps seeded this mental flowering? This video follows the ongoing excavations of Christopher Henshilwood, an archaeologist who is seeking the earliest evidence of our species' unique mental powers. Recent finds dating to 72,000 years ago at his South African excavation site, Blombos Cave, are slowly shedding light an era of human culture that has been all but dark.

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Jewels of a Creative Mind

If your clothes could speak, what would they say? Whether you’re wearing a uniform, diamond jewelry, or a concert t-shirt, your outfit sends a message without you having to utter a word. It hints at what you like to do, where you live, and what group you belong to. Showing off your identity this way is an innate human urge. In fact, scientists consider it a trademark of our species. No other organism, not even our hominid ancestors, can use clothes and jewelryas well as words, images, music, and other symbolsto express themselves. Our unique ability to devise and exchange messages with infinite combinations of symbols is called symbolic thought.

When did our symbolic mental powers first appear? This is one of the thorniest questions still unanswered by researchers of human evolution. Minds, of course, don’t fossilize. Scientists cannot trace the evolutionary development of the brain like that of bone structure. Furthermore, they are only beginning to comprehend how the modern human brain works at all. “We have no idea how the brain translates a mass of electrochemical symbols into what we subjectively experience as consciousness. As long as we don’t understand that, we really won’t know what symbolism means in terms of brain architecture and mental process,” says Ian Tattersall, curator of anthropology at this museum. “On the other hand, we can infer cognition from artifacts that appear to embody symbolic meanings, and that is where we have to look.” Jewelry, art, and other artifacts from archaeological digs help trace key changes in our species’ cognitive functions over time.

This is why a set of ancient beads unearthed in South Africa’s Blombos Cave in 2004 made such a stir. The beads—41 pearly snail shells pierced for stringing—offered the first proof that humans were using symbols for self-expression as far back as 72,000 years ago on the African continent, where humankind emerged. This has unseated a view widely held among archaeologists that modern human thought began to appear in Ice Age Europe, around 40,000 years ago. Although beads even older than those at Blombos have since been announced, archaeologists continue to scour the cave for evidence of uniquely human behaviors deeper in antiquity.

What Makes Us Modern?

Fossil and genetic evidence tells us that our species, Homo sapiens, first appeared between 200,000 and 160,000 years ago in eastern Africa. We’d recognize ourselves physically in these people, as they are the progenitors of all who live today. “They looked much like we look,” says Christopher Henshilwood, who leads the archaeology team at Blombos Cave. “You wouldn’t be surprised if you saw one of those people walking down the street. How they behaved in that time period is a very different challenge altogether.”

The first Homo sapiens are considered “modern humans” from an anatomical standpoint, but not from a behavioral one. Archaeological sites from this emergent period do not show characteristically “modern” behaviors such as symbolic thought, complex social structure, and the use of languageall capabilities rooted in the brain. “I think the human capacity for symbolic thought probably existed from the time of that biological reorganization that gave rise to Homo sapiens as a recognizable physical entity,” says Tattersall. “However, that capacity was not expressed until a long time later.”

How much later? Nearly all of the artifact evidence for symbolic thought dates to 40,000 years old and younger, well after groups of humans began to migrate out of Africa. At this time, those living in Europe began to adorn cave walls with lavish paintings, carve delicate ivory figurines and jewelry, and construct multi-part hunting devices such as arrows and harpoons. The evidence is so copious that the period has been dubbed “the creative explosion.” For decades, the prevailing view was that the modern symbolic mind first emerged during this period.

The challenge for archaeologists, then, is to trace the behavioral evolution of humans in the interval between our emergence in Africa to the time of the creative explosion. And it is quite challenging. Not only do artifacts that old rarely survive the elements, but very few sites in that interval have been well excavated in Africa. The fragments of evidence that have been foundincluding the artifacts at Blombosare only now revealing that the modern mind evolved more as a “slow burn” than an explosion.

“One of the significances of Blombos,” says Henshilwood, “is that we now know that people did not evolve modern-type behavior in Europe. They were already modern before they left Africa. So our previous understanding of Europe being the cradle, if you like, of modernity has now been overturned, and Africa is now back in the spotlight again.”

At Blombos Cave

The low, wide mouth of Blombos cave faces the Indian Ocean on the southern coast of South Africa’s Western Cape. Only Antarctica lies beyond. Henshilwood, who is a professor at both the University of the Witwatersrand in South Africa and the University of Bergen in Norway, discovered the site in 1991. With colleagues, he has been excavating lower, older layers of the cave floor since then. The team has now reached a layer dated to 140,000 years old, and is still unearthing evidence that humans took shelter at the cave even then.

The people who used Blombos were not permanent residents. The artifactsmostly stone spear points and scrapers, seashells, and butchered animal bonesreveal that small groups stayed at the cave for weeks at a time to hunt and gather food. They’d collect abalone, mussels, and other shellfish from the tidal flats, trap rodents, and hunt antelope and fur seals. After they moved on to a new spot, sand would blow into the cave, covering the belongings the group left behind. “What we are looking at is almost a snapshot of life 70,000 or 100,000 years ago,” says Henshilwood. “We are trying to reconstruct human behavior in the past from a really limited set of information that we have available to us today.”

Telltale Signs

The Blombos team found the snail-shell beads underneath a three-inch-thick layer of orange sand dated at 70,000 years old. Judging from where this species of marine snail, Nassarius kraussianus, lived at that time, the bead makers must have gathered the shells from a river mouth about 20 km (12 miles) from the cave. They pierced the shells with a pointed bone tool and strung the beads as a necklace or bracelet, or applied them to clothing. The wear patterns on the shells are not found in nature, and indicate the beads had rubbed against thread, skin, or other beads. What’s more, residues of a red pigment called ochre speckled the shells. This suggests that pigment on the wearer’s skin had rubbed off on the jewelry, or that the jewelry itself was once tinted red.

Chunks of brilliant red ochre, in fact, turn up often at the Blombos cave site. Ochre is a soft, greasy stone that can be used as makeup. Ochre’s high iron content can render it white, yellow, orange, or red. Even today, people in certain African cultures smooth ochre on their skin to create distinctive markings. “I think ochre had an important role in the lives of the [Blombos] people after about 150,000 years ago,” says Henshilwood. “People were putting it on their faces or on their bodies, perhaps even making patterns to indicate some kind of meaning.”

So far, Henshilwood’s most tantalizing discovery at Blombos is a chunk of ochre rubbed flat on one side and engraved with a geometric pattern. It also turned up beneath the orange sand layer. To find such an object surviving 72,000 years is a triumph for archaeologists. Unearthed in 2000, this ochre piece is still thought to be the earliest evidence of what may be called “art.”

A Picture Emerges

Two more recent bead finds in caves in Morocco (dated to 82,000 years old) and Israel (100,000 to 135,000 years old) strengthen the Blombos discovery. At both sites, the beads are made of Nassarius gibbosulus, a relative of the snail used at Blombos. The beads at the Moroccan site also have red ochre residue. This evidence, although limited, is slowly revealing that bead-working practiceand thus the earliest glimmers of symbolic thoughtwas common and perhaps widespread among early humans in Africa and the Levant long before groups migrated to Europe.

What the objects at these three sites symbolized to the people who used them is impossible to say. As far as Henshilwood will speculate, they may have served to send messages within or among groups. At 72,000 years ago, the human population was extremely low and widely dispersed around a vast African landscape. Art and adornment helped people connect, communicate, and trade with others to weave our social fabric at the dawn of human cultures. “I don’t think things were different then,” says Henshilwood. “Groups had identity,” as they still do today.