Small stone blades and a reddish body pigment recently discovered in a cave near the southern tip of South Africa suggest that the use of symbolism and tools -- hallmarks of modern human behavior -- had already begun to develop 164,000 years ago, far earlier than previously believed, researchers report.
Arizona researchers also found in the cave the earliest evidence of seafood consumption. The earliest previous evidence of the consumption of shellfish was dated to 125,000 years ago, and the oldest stone tools, known as bladelets, were 70,000 years old.
Researchers know that modern humans evolved in Africa between 100,000 and 200,000 years ago, but there has been little archeological evidence available to pin down a timeline.
Evidence along the coastlines has been particularly scarce because rising ocean waters after the end of the last glacial period obliterated most sites.
The new evidence comes from a cave at Pinnacle Point on Mossel Bay, about halfway between Cape Town and Port Elizabeth. The cave would have been two to three miles inland at the time it was occupied, high enough above sea level to be safe from flooding.
A team headed by anthropologist Curtis Marean of Arizona State University's Institute of Human Origins reported Thursday in the journal Nature that it found shells from cooked seafood in the cave, including brown and black mussels, small saltwater clams, sea snails and even a barnacle, which is typically found on whale blubber or skin.
Seafood was the last item added to the diet of humans before they began to domesticate animals and grow their own food. Marean said the ancient humans brought the shellfish to the cave and cooked it over hot rocks, which caused it to pop open. When Marean's team replicated the process, they found the food tasty but a little dry, he said.
The small bladelets, about the size of a pinky finger, are thought to have been attached to spears, often in multiples, providing an advantage over hand-held tools.
The red ocher pigment, found in the form of 57 lumps of hematite collected by the cave dwellers, would have been used for decorating their bodies and coloring artifacts. Such decoration is thought to be an early manifestation of symbolism. The decoration was used to convey messages to other peoples living in the vicinity.
Africa was cold and very dry during this period, and Marean and his colleagues speculated that the shellfish were a kind of "starvation food" the early humans turned to when there was little else available.
Evidence indicates there were only a handful of places in Africa where humans could have survived during this glacial period. Mossel Bay may have been one of them, they said.
"It is possible that this population could be the progenitor population for all modern humans," they wrote.