Is Bead Find Proof Modern Thought Began in Africa?
for National Geographic News
|March 31, 2004|
Ostrich-eggshell beads found in Africa show that human beings were capable of symbolic thinking much earlier than previously thought, a team of scientists reports.
Anatomically modern humans (homo sapiens)people who looked pretty much like we do nowarose in Africa around 130,000 years ago. The question debated by archaeologists and anthropologists is: How smart were they?
One school of thought holds that while early human ancestors became anatomically modern while still in Africa, the development of modern behavioral traits lagged, emerging relatively suddenly only about 45,000 years ago. Around that time waves of modern humans began leaving Africa and colonizing the rest of the world.
Proponents of the cultural-lag idea suggest that a sudden genetic change, an increase in population density that spurred technological and cultural innovation, or other factors triggered the exodus out of Africa and the explosion of cultural change which occurred in Europe.
Others argue that "behavioral modernity" evolved in Africa and has a much longer history.
The ostrich-eggshell beads recovered from a site in the Serengeti National Park in Tanzania are believed to be about 70,000 years old, according to a team of scientists.
The team is speaking today at the annual meeting of the Paleoanthropology Society taking place this week in Montreal. The research was supported in part by the National Geographic Society's Committee for Research and Exploration and the Leakey Foundation.
If the dates are correct, there was modern human behavior in Africa about 35,000 years earlier than previously thought, strengthening the argument that "behavioral modernity" evolved hand-in-hand with anatomical modernity.
Beads are "unambiguous examples of symbolic behavior," said Curtis Marean, one of the paper's presenters. Marean is an anthropologist at the Institute of Human Origins at Arizona State University. "Once we get some definitive dating, [the find] could have a major impact on the evolution of symbolic thinking."
Complicating the debate is the fact that there is no consensus definition for what constitutes modern behavior.
Beadmaking is considered evidence of symbolic thinking becausewhether used for jewelry to show status or group identity or used in tradeit has little to do with survival. Other traits thought of as "modern" include the ability to plan ahead, innovate technologically, establish social and trade networks, create art, and adapt to changing conditions and environments.
Late Stone Age (beginning about 45,000 years ago) sites in Europe abound with cave paintings, sophisticated bone tools, and evidence of complex burial rituals, which signal symbolic thinking.
During the Late Stone Age people began constructing permanent shelters rather than depending on caves. They figured out how to catch large fish and hunt more aggressively, and they developed weapons that could be thrown.
Tools made out of bones or antlers are commonly found at Late Stone Age sites, and they are more specialized and complex than the stone tools of the Middle Stone Age (beginning about 280,000 until 45,000 years ago) found in Africa.
Until recently very little evidence of symbolic thinking during the Middle Stone Age has been found in Africa. There are advocates of the idea that the capability was always there, but that it wasn't expressed. There have been no fundamental changes in human anatomy in the last 50,000 years, and it simply took us this long to send people into space or develop computers, these advocates believe.
Others argue that the record is scant in Africa because very little archaeological work has been done on the continent. By contrast, European archaeological sites have been mined extensively and for decades.
This is beginning to change. Work published in 2001 described 28 bone tools and thousands of pieces of ochera mineral used to create paint for body decoration and cave paintingdated at roughly 70,000 years old found in Blombos Cave in South Africa. Two pieces of ocher appear to be marked with abstract lines that could be viewed as artistic expression.
The archaeological record is also open to varying interpretations.
Alison Brooks, an anthropologist at George Washington University in Washington, D.C., supports the idea of continuous innovation. She says archaeological evidence suggests that modern humans in Africa 120,000 years to 50,000 years ago were transporting raw materials for distances up to 186 miles (300 kilometers). They were capable of fishing and created sophisticated tools and weapons, she says.
Advocates of the gradual evolution of modern behavior argue that, as more sites in Africa are fully excavated, evidence will accumulate that indicates that cultural modernity was widespread in Africa during the Middle Stone Age.
Archaeological Great Divide
Richard Klein, an anthropologist at Stanford University and author of several books on human origins, argues that modern behavior appeared rapidly, possibly as the result of a genetic change that facilitated our use of language.
Regarding the disputed interpretation of the Blombos Cave artifacts, Klein said, "Art is in the eye of the beholder, and so there will always be debate about whether something is really art."
Klein continued, "The real problem is that if you look at sites that are 40,000 years old or younger, art is everywhere, and everyone agrees it's art. You also find bone artifacts, complex burials, and other indicators of modernity. Beyond 40,000 years you might find one of these but never in a package, and nobody agrees."
Ostrich-shell beads such as those found at the Serengeti site would certainly be evidence of a fully modern mind, Klein said. The problem is in establishing correct dates.
Radiocarbon testing loses its efficacy on objects more than 50,000 years old. Also contamination of an object with more recent radiocarbon, leading to an inaccurate date, is always a threat and difficult to detect. Furthermore, ground shifts, heavy rains, or a later site occupation could cause more modern objects to become mixed with those from an older site.
Human origins specialists do all agree on one thing.
"Ultimately it is going to take wider excavation to resolve the questions," Arizona State University's Marean said.
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