Shells Offer New Take on Human Evolution

March 30, 2009 -- Analysis of complex shell tools is rewriting the history of human development.

To understand human development, archaeologists tend to analyze either fossilized human bones or stone tools. In Africa and Europe stone tools are seen to increase in complexity over the last few million years.

But in East Asia, Southeast Asia, Australia and New Guinea, stone tools don't appear to develop until the last 4000 years.

Katherine Szabo of the University of Wollongong in Australia has just taken up this issue, saying it "bears on questions of our history as a species."

Szabo explained the lack of stone tools found in these regions has led some researchers to conclude that this region was "static," with some dubbing it "culturally retarded."

Others argue that, like the hunter gatherers of today, humans in East Asia, Southeast Asia, Australia and New Guinea relied on plants, such as bamboo, rather than stone, and these aren't preserved in archaeological record.

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"That may very well be true but we can't prove it," said Szabo.

She said researching shells is exciting because it can be preserved for just as long as stone in the archaeological record.

"It's not a material that anyone's looked at or that anyone particularly understands very well," said Szabo.

In published research to date, Szabo reports having excavated shell tools dating back 32,000 years from a cave site in eastern Indonesia, and comparing them with stone tools from the same cave.

"It transpired that the shell tools were in fact much more complex to produce than the stone tools," she said.

The stone tools were randomly chipped, but the shell tools had been carefully chosen and shaped.

In one case, a "cats eye" or operculum shell was flaked systematically with five blows, each one slightly overlapping with the last in a clockwise direction.