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Stone Age tools go south

Submitted by coldrum on Friday, 06 February 2009  Page Views: 2259

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Although separated by several thousand kilometers, southern and eastern Africa were, in a sense, a stone’s throw from each other ancient times. New evidence suggests that human ancestors in southern Africa fashioned teardrop-shaped stone hand axes 1.6 million years ago, nearly twice as long ago as many researchers thought and about the time such tools are known to have first appeared in eastern Africa.

Ryan Gibbon and his colleagues dated hand axes and related stone implements, collectively known as Acheulean artifacts, using measures of the relative decay of radioactive forms of aluminum and beryllium in quartz grains from the soil and gravel bearing the artifacts. Exposure to cosmic radiation causes quartz to produce these substances, which then decay after enough sediment covers the quartz.

Acheulean finds have been dated to 1.7 million years ago in Ethiopia. Less-advanced stone tools have been dated to as early as 2.5 million years ago in eastern Africa.

Over two days in 2005, Gibbon’s group identified 465 stone tools brought out of a diamond-mining pit bordering South Africa’s Vaal River, near the town of Windsorton. Those implements included 10 hand axes, two hand axes with large chopping edges known as cleavers and two elongated, three-sided tools called picks. The researchers have since recovered another 100 hand axes, 30 cleavers and 40 picks from the Windsorton pit. Sand and gravel from five diamond-mining pits provided samples for dating, says Gibbon, an archaeology graduate student at the University of the Witwatersrand in Johannesburg.

Findings at Windsorton, published online December 20 in the Journal of Human Evolution, raise the question of whether human ancestors developed Acheulean tools independently in southern and eastern Africa at around the same time, developed the tools in only one area from which the tool-making tradition spread rapidly to distant regions.

Gibbon suspects that Homo ergaster, a species regarded as a direct ancestor of modern humans, made the Windsorton hand axes. A nearby South African site has yielded H. ergaster fossils, but no fossils of any member of the human evolutionary family have been found in the Windsorton vicinity. Fossil finds have linked H. ergaster to Acheulean tools in eastern Africa.

Stanford University archaeologist Richard Klein suspects that Acheulean tool making originated in eastern Africa about 1.7 million years ago and reached northern parts of what’s now South Africa shortly afterward. “I doubt it arose more than once,” he says.

“East Africa has always been considered the place of origin of stone tools and subsequent technological developments, but I wouldn’t be surprised to discover that significant stone-tool advances took place in the Vaal River basin and then spread to the rest of Africa,” Gibbon says.

His team’s findings support a preliminary age estimate of 1.6 million years that other researchers have reported for Acheulean artifacts from South Africa’s Wonderwerk Cave, located about 100 kilometers northwest of Windsorton. Anthropologist Michael Chazan of the University of Toronto and his coworkers dated quartz grains from artifact-bearing soil and further verified the ages by identifying reversals of Earth’s magnetic field with known ages in the cave’s sediment. Their study appeared in the July Journal of Human Evolution.

Additional dating of Wonderwerk Cave deposits has confirmed that Acheulean activity there began 1.6 million years ago, with even older stone tools dating to 2 million years ago, Chazan says.

Still, the precise timing of Acheulean origins in eastern and southern Africa remains uncertain. “There could easily be a time lag between the two regions on the order of 100,000 years, in either direction, that we are not yet able to detect,” Chazan remarks.

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Contributor Bio for coldrum: Based in Milkyway, contributing since 2002. Favourite site: Avebury.

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Brain changes may have led to Stone Age tools by coldrum on Thursday, 01 October 2009
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Brain changes may have led to Stone Age tools

Once upon a time in the long evolution of Homo sapiens, a band of our African ancestors learned to use fire for more than cooking meat, lighting the dark or warding off attacking animals.

Those Stone Age people became the world's first engineers - they discovered that the intense heat of a fire's embers could make chunks of stone much easier to flake for making tools, and to make them much sharper too.

It was "a breakthrough adaptation in human evolution," reports an international group of archaeologists and anthropologists. And it may have come about because of changes in those early human's brains, other scientists say.

What began at least 165,000 years ago became the most common method of stone toolmaking in Africa by about 72,000 years ago.

The scientists from Africa, Australia and Arizona analyzed nearly 200 ancient tools found around cave dwellings at a South African coastal site called Pinnacle Point, which earlier excavations had shown were inhabited by people of the Middle Stone Age.

The knives, scrapers and hand axes were made of a widely used type of silicate rock called silcrete. Some of the scientists, reporting in the current issue of the journal Science, are themselves skilled at "knapping" - the art of chipping stones by hand to create sharp tools - and their tools demonstrated the clear improvements possible from heat treatment at fire temperatures of 450 Fahrenheit or more.

Others explored the South African sites where they collected ancient silcrete tools that were deliberately heat-treated by the Stone Age people. They analyzed them with high-tech methods to reject any that may have accidentally fallen into hearth fires or been heated later in accidental bush blazes.

"Early modern humans regularly employed pyrotechnology to increase the quality and efficiency of their stone tool manufacturing process," wrote team leader Kyle Brown of South Africa's University of Cape Town and the Institute of Human Origins at Arizona State University in Tempe.

That ability to "alter and improve available raw materials and the quality and efficiency of stone tool manufacture may have been a behavioral advantage" over others, including the Neanderthals, Brown and his colleagues wrote.

At UC Berkeley, anthropologist Steven Shackley noted that in California and elsewhere in the American Southwest, the people of the well-known Clovis culture who had migrated from Siberia across the Bering land bridge some 13,000 years ago also used fire to temper their stone tools - apparently their own age-old technology.

"So for those earlier Stone Age people of 100,000 years ago, this report suggests that something was going on in their brains and something was changing the forms of their hands to make that improvement in stone tools possible," Shackley said.

Katherine Pollard, a biostatistician and human genome analyst at the Gladstone Institutes in San Francisco, supported Shackley's conjecture that changes in brain DNA may have endowed those Stone Age folks with new toolmaking skills.

"It seems almost certain that there were some genetic changes involved," she said in an e-mail. "These may have affected our ancestors' brains, but could also have been involved in manual dexterity or vision or other systems.

"It will probably be a while before we can link specific genetic changes to specific neurological changes and then to events in the archaeological record. We just don't really know that much yet about how our brains work. But, it will be cool to see how these stories unfold."

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/08/26/MNHK19AS41.DTL&type=science#ixzz0PRydkcPh

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Ancient Weapons Point to First Use of Fire for Tools? by coldrum on Thursday, 01 October 2009
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With the tell-tale sheen of heat-treated rock, a 72,000-year-old cache of stone weapons found in Africa suggests humans began using fire to create tools nearly 50,000 years earlier than previously thought, a new study says.

Scientists had thought people began manipulating fire to create tools in Europe about 25,000 years ago.

But the new finds suggest that people in what is now South Africa discovered that heating a stone called silcrete would make it easier to flake, allowing them to shape more advanced blades, knives, and other tools.

These early engineers likely used some of these tools, mounted on handles, to hunt and butcher wide range of prey, from the aggressive Cape buffalo (Cape buffalo picture) to the tiny mole rat, according to the authors of the study, to be published tomorrow in the journal Science.

Birth of Modern Humanity?

This sophisticated control over fire reflects advanced smarts, and marks the turning point when we became "uniquely human," said study leader Kyle Brown, an archaeologist at the University of Cape Town in South Africa.

"These people were extremely intelligent," Brown said. "These are not the image of the classic cavemen, of brutish people that are stumbling around the landscape and, in spite of themselves, surviving.

"These are the people that [may have] even colonized the rest of the world," he said.

As part of the study, the researchers replicated the processes the early Africans likely would have used to make the stone tools. HeaBut paleoanthropologist John Shea isn't convinced by the idea that "heat treating" stone was a sign of the transition to modern human behavior.

"People rush immediately to look for evidence of a transforming event in the course of Homo sapiens evolution to distinguish modern humans from so-called early ones," said Shea, of Stony Brook University.

ted over a fire pit, the silcrete flaked and took on a glossy red color.

Such craftsmanship required thinking ahead, a sign of high intelligence, Brown said. People had to collect firewood, build the fire, work the stone, and then afix the handle to the stone using natural adhesives.

"My position is that you shouldn't assume this transformative event—you have to prove it," Shea said.

To begin with, scientists would need to verify that the various human species preceding H. sapiens in South Africa did not also heat-treat stones.

Even so, Shea praised the study, saying it will inspire people to seek out other heat-treated stone tools undetected in the African record.

Showing Off?

The tools were apparently created during a burst of cultural growth, when the human population was slowly recovering from a severe glacial period.

At the South African sites, humans were designing jewelry, such as shell beads, and grinding up ochre to paint themselves and decorate their caves, study leader Brown said. (See "Oldest Jewelry? 'Beads' Discovered in South African Cave.")

Heat-treating stone could have been "one of the technologies in their toolkits that allowed [them] to adapt to different areas as they expanded out of Africa," Brown said.

(Related: "Innovation Linked to Human Migration Out of Africa.")

But heat treatment probably didn't improve the tools, and may have even made them more likely to shatter, Harvard's Shea said.

Instead the flashy artifacts might have been ways that "some humans showed off that they had time on their hands," Shea said.

"Going into woods with a bunch of arrows that would shatter on impact is another way of saying, I'm a really good hunter; I don't need backup."



"Because [this is] such a sophisticated technology, this is something that would involve language to pass it on to the next generation," he added.


http://news.nationalgeographic.com/news/2009/08/090813-first-fire-tools.html
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