Cave finds make point about early humans.

Much anthropological attention is focused on whether anatomically modem humans emerged in Africa some 100,000 years ago. A related question of increasing concern is whether sophisticated tool making and other advanced cultural behaviors emerged in the earliest representatives of our species or much later, beginning perhaps 40,000 years ago.

Sparse and often contested archaeological evidence exists for cultural innovations by the earliest modern humans. Now, a report in the December Current Anthroplogy details two sharpened bone artifacts that date to more than 40,000 years ago.

The artifacts, along with associated remains of stone points and large fish apparently caught for food, add weight to arguments for more ancient advances in tool manufacture and social activity, contend Christopher Henshilwood and Judith Sealy, both archaeologists at the University of Cape Town in South Africa.

Henshilwood and Sealy have conducted excavations at Blombos Cave, located just off the coast near the tip of South Africa. Fieldwork earlier this year and in 1993 yielded more than 20 bone artifacts. These include two thin bones--each about 2 1/2 inches long--that were ground and polished to a point at one end and one bone fragment bearing a series of parallel grooves. Incisions on the latter were probably made with a single stone tool, either to remove meat from the bone or to produce a decorative image, the researchers hold.

Sharpened stone points and the remains of shellfish and large fish were found in the same sediment as the bone specimens. Radiocarbon dates for one piece of charcoal and four shell samples from this soil indicate that their age exceeds the limit of carbon dating, which goes back about 40,000 years.

The bone artifacts and associated animal bones also display low concentrations of nitrogen and carbon. These substances would have leached out of the bone during a long period of burial. Animal bones found in more recent soil layers at Blombos Cave exhibit much higher concentrations of nitrogen and carbon, the researchers note.

The tip of one bone point is slightly darkened, suggesting that it may have been heated over a fire in an attempt to harden the bone, according to Henshilwood and Sealy Both bone points were fashioned so that they could be attached to poles or handles and used as spears or harpoons, they maintain. Stone points found in the South African cave also contain tab-shaped areas at their base that could have been lashed onto handles or shafts.

Examples of bone tools that date to between 150,000 and 40,000 years old are rare (SN: 4/29/95, p. 260). The Blombos Cave finds indicate that at least some of the people living during that period regularly made and used bone tools, Henshilwood and Sealy conclude.

"These are very intriguing bone points," remarks archaeologist Stanley H. Ambrose of the University of Illinois at Urbana-Champaign. "It's possible that they're more than 40,000 years old, but the evidence is not yet conclusive."

Ambrose awaits a more extensive analysis of sediment layers in Blombos Cave before accepting the minimum age proposed by Henshilwood and Sealy.

Based on the tools' condition and other archaeological evidence, Ambrose says that prehistoric humans apparently carried the bone points around with them, sharpened and otherwise maintained the implements from time to time, and eventually discarded them in the cave.