Clues to why modern humans migrated...

By Time of article published Nov 21, 2008

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By Shaun Smillie

In a cave 70 000 years ago, something strange was beginning to happen.

The occupants, who once lived in the cave, were behaving differently from their forefathers.

They were producing some of the first examples of jewellery and developing new technologies that were to give them an edge in years to come.

It wasn't an isolated event, across the African continent, the same thing was happening among bands of hunter gatherers from the Western Cape to Morocco.

What sparked this, no one knows.

It was so dramatic that some believe it might originally have been caused by a sudden change in the structure of our ancestor's brains.

That cave is Sibudu Cave, situated near Tongaat, in KwaZulu Natal, and it is here that an international team of scientists are unearthing the clues to this event and are trying to make sense of it all.

Their findings were published as part of a larger southern African dating project, in the journal Science at the end of October.

What they found in the cave were minute seashells that were likely strung together to make a necklace, bone arrowheads and the residues of what is possibly the earliest example of glue.

Also present were finely-crafted stone tools never seen before in earlier deposits.

These tools were probably parts of spearheads.

To archaeology professor Lyn Wadley of Wits University this haul reveals the earliest workings of what she calls complex cognitive behaviour.

In these artefacts, dug from the bottom of the cave are the signs of some of humans' earliest known attempts at making jewellery.

"We now know that these beads are 70 000 years old.

"Similarly-aged perforated seashells were discovered in Blombos Cave, Western Cape," Wadley explained, from Sibubu where she is continuing with her dig.

These changes happened in the space of about 5 000 years, an extraordinary short period of time, in the span of evolution.

Wadley is part of a team that includes Dr Zenobia Jacobs and Professor Richard "Bert" Roberts from the University of Wollongong, Australia.

For these Australian scientists, what has come out of Sibubu cave could help explain what motivated the first modern humans to migrate out of Africa, about 80 000 years ago, and later island hop from Asia to Australia.

New technological know how gave the migrating humans an advantage.

"With the perforated seashells we see people demonstrating that they are part of a group, or a particular status within that group.

"The use of personal ornamentation is evidence of symbolic behaviour even today," said Wadley.

The team has also found traces of red ochre which could have been used to paint ornaments.

Helping the team in their research was some high-tech gadgetry that aided them in piecing together how those cave dwellers lived all those years ago.

With the help of a microscope the academics found traces of residue on some of the stone tools. It turned out to be plant gum mixed with red ochre, and was probably glue.

"Making such glue and using it to attach a spearhead to a shaft requires complex cognitive abilities because it involves holding many things in mind during the process," Wadley said.

Earlier this year Dr Lucinda Backwell of the Bernard Price Institute for Palaeontological Research revealed that Sibubu Cave had produced what was believed to be the first bone arrow head, aged between 65 000 and 62 000 years.

The arrowheads may have been used for hunting blue duiker and plains game, then found close to the cave.

Again Wadley stressed that making such arrowheads and figuring out the technology that goes with manufacturing bows would have required a leap in thinking.

The team was even able to ascertain through studying burnt charcoal what these early humans were using for firewood.

In the ancient ash were found charred bones, many of them smashed so as to get at the nutritious marrow inside.

A microscopic study of the sediments in the cave revealed seeds that suggested that bundles of reeds were used as early mattresses.

It wasn't just at Sibubu that early humans were showing the innovation that today we take for granted.

Similar artefacts have been found in Morocco and at other archaeological sites in South Africa and Wadley believes these developments occurred independently of each other.

As to what triggered this change in early human behaviour, Wadley suggests that it might be up to academics in other scientific fields to answer that question.

"It might have been some sort of genetic mutation that made early people able to think in a modern way, but this suggestion needs to be followed up by someone other than an archaeologist," she said.

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