A large set of specialized bone tools found recently in a South African cave is forcing archaeologists to rethink their ideas about when "modern" human behavior emerged. The issue has been a key question in debate about human origins.
The discovery shows conclusively that early Homo sapiens come "out of Africa" with already well-developed skill in crafting tools of bone. Many archaeologists regard the introduction of bone tools as a key indicator of "modern" behavior in humans.
Dating analysis revealed that the tools are all more than 70,000 years old, which is considerably earlier than humans were thought to acquire bone technology.
Until now, scientists had concluded that early human ancestors became anatomically modern while still in Africa but lagged in modern behavioral traits until after they migrated to Europe and elsewhere.
"The implications are that there was modern human behavior in Africa about 35,000 years before Europe," said archaeologist Christopher Henshilwood, who is affiliated with IzikoSouth African Museum in Cape Town and the State University of New York at Stony Brook.
"What has been suggested up until now," he said, "is that modern human behavior was a very late occurrence that though people were anatomically modern in Africa from about 150,000 to 100,000 years ago, they remained behaviorally non-modern until about 40,000 or 50 000 years ago, when they suddenly changed and then moved into Europe and elsewhere."
Henshilwood is the lead author of a forthcoming study that argues, based on the bone tools and other recent discoveries, that "behavioral modernity" first evolved in Africa and has a much longer history than most archaeologists believe. The study is scheduled for publication in the December issue of the Journal of Human Evolution.
Ancient Tool Industry
The study involves a detailed description of 28 bone tools and related artifacts that were recovered from Blombos Cave, in a cliff overlooking the Indian Ocean at the southernmost tip of South Africa.
Although other bone tools of about the same age have been discovered at other sites in Africa, the findings have been single tools or the context has been disputed. The artifacts from Blombos provide the first indisputable evidence of an existing Middle Stone Age bone tool industry, the researchers say.
Scattered within the layers in which the stone tools were found and in layers above it were double-faced stone points, possibly used as spearheads. Similar stone points found at other sites in the southern Cape date to about 65,000 years ago, which suggests that the Blombos bone tools are at least as old.
Furthermore, the geologic layers have distinctively different kinds of sediments that helped the scientists determine the period in which the bone tools and other materials were deposited.