Ancient axes hint at earlier 'out-of-Africa' exodus: study

PARIS: Scientists reported Thursday the discovery of stone tools that challenge conventional timelines for the out-of-Africa exodus of early humans to Asia and Europe.

Double-sided stone axes, along with other implements, found in Kenya are at least 300,000 years older than previously known samples of the same distinctive technology, known as Acheulian.

Breakthroughs in the design and manufacture of tools mark watershed moments in human evolution.

The emergence of Acheulian techniques in particular are thought to closely coincide with key changes in human brain development, suggesting they were both an expression and a catalyst of enhanced cognitive prowess.

An earlier, more primitive class of tools, called Oldowan, wielded by more distant forebear starting about 2.5 million years ago were essentially flakes of stone chipped from a large rock.

"For the Acheulian tools, were are looking at a very different manufacturing process," explained Helene Roche, an archaeologist at Universite Paris Ouest and a co-author of the study, published in Nature.

"The aim was less to create flakes, than to give shape to the larger object they came from," she said by phone.

In a further innovation, pear-shaped and two-edged hand-axes were further "retouched" using bone, antler or even wood.

Up to now, Acheulian industry, including the emblematic double-faced axe, was thought to have truly emerged about 1.4 million years ago, well after the
first migration of hominins, or early humans, out of east Africa.

Using a dating technique called palaeomagnetism, however, researchers from France and the United States showed that the recently discovered tools are at least 1.76 million years old.

The timing and location make a good fit with the earliest definitive specimen of the big-brained Homo erectus, generally assumed to be the first hominin to leave Africa.

But even as the findings shed light on one question, they raise another: If this cutting-edge technology was already well established when the first early human migrants left the continent, why didn't they take it along?

That they did not is nearly certain: "The Acheulian did not accompany the first human dispersal from Africa despite being available at the time," the researchers conclude.

Indeed, the new-and-improved tools did not show up in Asia, the Middle East or Europe until at least half-a-million years later. Why?

The study, published in Nature, does not provide a smoking-gun answer, but does point to several possibilities.

Perhaps two groups -- either distinct species such as Homo erectus and Homo habilis, or different "cultures" within one species -- co-existed in Africa about 1.76 million years ago, but only one was clever enough to develop the more durable and precise Acheulian tools, the researchers speculate.

Under this scenario, it was members of the other group, presumably bearing Oldowan-style artefacts, that left Africa behind.

But co-author Jean-Philippe Brugal, a researcher at France's National Centre for Scientific Research based in Aix-en-Provence, has another theory.

"The findings suggest to me that ancient man may have left Africa before this time, perhaps two million years ago," he said by phone.

An earlier out-of-Africa scenario remains conjecture, but there is no doubt that there were several waves of migration from the continent.

It is more likely that the Acheulian technology that began showing up beyond Africa's shores far later was imported by one of these migratory forays, rather than having evolved separately, he added.

"There are no neat boundaries here, different populations and tool technologies overlap in time and place. It is not a simple storyline." (AFP)