It seems that the cave dwellers favored the bright red pieces the most, because those showed more signs of scraping or rubbing.
The cave also held stone blades of various sizes, from about 1 to 2 inches (2 to 5 centimeters) long, along with larger rocks used as raw material for making the tools.
"The bladelets are so small, they're very hard to hold in your hand and use," Marean said.
This suggests they were part of more sophisticated tools, with the bladelets mounted in handles of bone or wood, he added.
Similar bladelets have been found in only one other site that might be earlier, called Twin Rivers, in Zambia.
However, the estimated dates of the Twin Rivers bladelets are uncertain, ranging from 140,000 to 400,000 years old.
Before the Pinnacle Point find, the earliest securely dated bladelets were 70,000 years old, Marean said.
The team's findings appear in tomorrow's issue of the journal Nature.
Ice Age Survival
The new finding suggests that people had learned to live on the coast soon after anatomically modern humans arose about 195,000 years ago.
Marean and colleagues argue that eating seafood also could have helped some early humans survive an ice age that lasted from about 200,000 to 130,000 years ago.
During that time, Africa was cool and dry, and the ocean could have been a more reliable source of food.
Sally McBrearty of the University of Connecticut and Chris Stringer of London's Natural History Museum wrote a commentary, also published in Nature, on the new findings.
"The Pinnacle Point evidence is significant because it suggests that early humans in Africa inhabited a cognitive world enriched by symbols before 160,000 years ago," McBrearty and Stringer wrote.
(Read related story: "'Python Cave' Reveals Oldest Human Ritual, Scientists Suggest" [December 22, 2006].)
Jon Erlandson, of the University of Oregon in Eugene, told National Geographic News that the new findings are "significant."
But he added that evidence of seafood consumption is not surprising.
"I suspect the use of shellfish goes back a lot earlier than this," he said.
Foraging in intertidal areas of coasts is "a no-brainer," Erlandson added. "Baboons do it; birds do it."
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