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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