Stone Tools Hold New Clues About Human Evolution

May 5, 2000 - Reuters

Ancient stone tools found on the Red Sea coast of Eritrea in East Africa are providing new clues about the evolution and migration of modern humans, scientists said Wednesday.

The 125,000-year-old tools unearthed by American and Eritrean researchers are the earliest well documented evidence of when modern humans adapted to a marine environment and a new way of providing food.

They also support the ``out of Africa'' theory -- that humans evolved from a common ancestor in Africa and spread across the world.

``It represents a whole new kind of adaptation and feeding strategy that we suspect may have been influenced by climate change,'' Robert Walter said in a telephone interview.

The geologist at the Centro de Investigacion Cientifica de Educacion Superior (CICESE) in Mexico said the tools could indicate that humans were essentially forced out of their native habitat in the interior of Africa because of the glacial cycles at the time when the climate cooled and dried dramatically.

``We suspect this may have shrunk the fresh water environment, forcing them into new habitats,'' he added.

Walter, who collaborated on the research with Yoseph Libsekal of the University of Asmara in Eritrea and a team of international experts, used uranium-series dates to determine the age of the tools.

``We were able to date the sequence of coral and shallow marine sediment in which the tools were discovered very accurately and very precisely to 125,000 years ago,'' he added.

So far they have found no evidence of who made the tools but they think human adaptation to a marine habitat spread quickly along the coast of Africa.

``We are documenting for the first time that coastal marine sites are viable places to search for early human activity,'' said Walter.

The research, reported in the latest edition of the science journal Nature, also suggests possible routes for the migration of modern humans out of Africa.

``There are two ways this could have happened. The most logical way would have been northward, along the coast of the Red Sea into the Levant (the eastern Mediterranean coast),'' Walter explained.

There could also have been a southern route along the Red Sea close to the Arabian peninsula, where modern humans could have crossed over a land bridge that may have connected the two continents.

``Either one of those two methods is viable,'' he added.

In a commentary on the research, Chris Stringer of the Natural History Museum in London said the research implied that at least ``one dispersal of modern humans from Africa must have occurred during the Middle Palaeolithic (100,000 years ago) and that characteristic elements of modern human behavior existed by then.''

Oldest Stone Axes in China Found

March 3, 2000 - Journal of Science

Eight hundred thousand years ago, a meteorite blasted into what is now Vietnam, burning forests, killing off wildlife and probably badly frightening the pre-humans who lived there.

But eventually, the hominids came back, perhaps having survived the explosion in limestone caves or perhaps wandering in from neighboring regions decades later.

They found a freshly exposed outcropping of rock, perfect for making stone tools. Archeologists said on Thursday they found those tools -- the oldest stone axes ever found in China.

The tools, which are about 803,000 years old, demonstrate that early humans living in the region had a similar degree of technological expertise as those living in Africa.

They say the tools show that the Asian Homo erectus was every bit as advanced as his African cousins and suggest this species of early humans shared a global culture.

``The early humans in China, in eastern Asia, were not part of some cultural backwater,'' Rick Potts of the Smithsonian Institution in Washington, who helped lead the study, said in a telephone interview.

``They had the competence and the smarts to do exactly what hominids were doing in other parts of the world.''

Potts and colleagues at the Chinese Academy of Sciences in Beijing were exploring an area in Guangxi Zhuang Autonomous Province, near the border with Vietnam in southern China.

The area is part of an ancient blast zone that has been well documented. Tektites -- little pieces of broken stone associated with meteorites -- have been found scattered across southeast Asia and as far south as Australia.

Potts said no one knows whether the meteorite hit the ground and broke up, or exploded just above ground level, throwing up earth and broke rocks. Either way, it was devastating.

``It would have killed off life close to the impact area or entry area. It must have been an awful place to have been at the time,'' he said.

``It seems like the ground zero would have been Laos, Cambodia, Vietnam,'' he added. ``No impact crater has been found but it may have been covered over.''

What has been found is a rich collection of stone tools. Potts and colleagues report in the journal Science that they have dated the tools and the tektites to 803,000 years ago.

``What we also found to our surprise at the time was that at the layer of these tektites there were also microscopic pieces of plant fragments, of burned wood, of charcoal,'' Potts said.

``What that indicates was that there was a lot of burned wood. I think it is evidence of fairly massive deforestation.''

It is known that Homo erectus lived in the area at the time. ``They would have been greatly affected by this,'' Potts said. ``It's a darn shame we don't have fossil bones from this area.''

But his team is digging in nearby limestone caves to see if they can find any.

Potts thinks the evidence so far tells a good tale, however.

``The fire would have actually really destroyed the forest and that would have exposed these large outcrops of stone,'' he said. ``Large, large areas of exposed cobbles would have been available. Under those conditions that local and regional populations moved back in and made stone tools.''

Potts specializes in studying how environmental change helped force the ancestors of humans to adapt and change. He thinks the blast zone is evidence of how curious and innovative early humans turned disaster to their advantage.

``There has been this long, over 50 years, viewpoint that because we don't find stone tools in eastern Asia like what we find in Africa, that there must have been great deep cultural isolation and behavioral differences,'' Potts said. ``This suggests that this is not the case.''

Prehistoric Tropical Tools: Form Not Related To Function

November 11, 1999 - University Science

There is a standard archaeological theory that at the end of the last ice age, prehistoric people in the tropics changed the form and shape of their stone tools so that they could utilize a wider range of food sources than those available just from hunting.

But Dutch researchers have now discovered that there was in fact no such correlation between tools and the climatic change that took place ten thousand years ago.

Their conclusion is based on a study of eight hundred flakes from sites in Colombia on the high plains of Bogot´┐Ż, in the valley of the Magdalena river and in the Amazon rain forest.

The belief that inhabitants of the tropics adapted their technology as a result of climate change was based in part on flakes from another Colombian site, at Tequendama. Many different types of stone tools have been found there and archaeologists assumed that each of them had a special function.

Flakes with concave edges were supposed to have been used for working wood; the increase in the number of flakes with concave edges after the last ice age was thought to be a direct result of the increased area of woodland in the Andes.

Now this theory has been shown to be untenable.

The Leiden University team that came to this conclusion were carrying out their research in the framework of a project organized by the Netherlands Organization for Scientific Research (NWO) Foundation for the Advancement of Tropical Research (WOTRO).

Their main conclusion: prehistoric man used his stone implements for a variety of functions, regardless of their shapes.

They reached this conclusion from the wear patterns on the implements and from microscopic fragments of hairs, collagen from bone, starch, pollen, and wood fibers which they found on the flakes. Indeed, the same types of implement appear to have been used for hunting, butchering carcasses and working wood.

The researchers were unable to discover any correlation between the form and the function of the flakes. (It was also notable that only somewhere between a quarter and half of the flakes had in fact been used.)

The Leiden archaeologists also concluded that prehistoric man in the tropics had hardly engaged in any specialization during the last ice age or in the first few centuries after it. Prehistoric peoples used flakes as and when they needed them, and with their simple tools were probably not dependent on any single environment, which allowed them to survive either on the cool upland plateaus or in the tropical forests.

The climate change taking place at the time therefore had no direct influence on their survival techniques, the Leiden team concluded.