490. Earliest Signs of Advanced Tools Found

 Tools like these axes are dated to
1.76 million years ago

By John Noble Wilford, The New York Times, August 31, 2011

One hallmark of Homo erectus, a forerunner of modern humans, was his stone tools, an advanced technology reflecting a good deal of forethought and dexterity. Up to now, however, scientists have been unable to pin a firm date on the earliest known evidence of his stone tool-making.

A new geological study, being reported Thursday in the journal Nature, showed that tools from a site near Lake Turkana in Kenya were made about 1.76 million years ago, the earliest of their ilk found so far. Previous dates were estimates ranging from 1.4 million to 1.6 million years ago.

Although no erectus fossils were found with the Turkana tools, a skull of that species was excavated last year in the same sediment level across the lake. This suggests that Homo erectus was responsible for these particular tools, which were made with what scientists refer to as Acheulean technology. The term connotes the type of oval and pear-shaped hand axes and other implements that were a specialty of early humans.

American researchers at the Lamont-Doherty Earth Observatory, part of Columbia University, established the age of the Turkana tools by dating the surrounding mudstone with a paleomagnetic technique. When layers of silt and clay hardened into stone, this preserved the orientation of Earth’s magnetic field at the time, and an analysis of the periodic polarity reversals and other records yielded the age of the site known as Kokiselei.

“I was taken aback when I realized that the geological data indicated it was the oldest Acheulean site in the world,” said the lead author of the report, Christopher J. Lepre, a researcher at Lamont-Doherty who also teaches geology at Rutgers University.

The assemblage of hand axes, picks and other cutting tools was collected, mostly in the 1990s, by French archaeologists led by Hélène Roche of the National Center for Scientific Research in France. Dr. Roche, a co-author of the paper, was steered to the site by Richard Leakey, the Kenyan fossil hunter who had discovered, just six miles away, the Turkana Boy, a young Homo erectus who lived about 1.5 million years ago and is the most complete early hominid skeleton found so far.

In the journal article, Dr. Lepre’s group said that artifacts from an earlier and simpler technology, Oldowan, were found alongside the more advanced Acheulean tools. The Oldowan tools were mainly sharp stone flakes and roughly worked rock cores, while the more sophisticated tools displayed signs of symmetry, uniformity and planning.

The presence of both Oldowan and Acheulean artifacts at the site indicates that “the two technologies are not mutually exclusive” components of an evolving cultural lineage, the scientists said. It was possible that the Acheulean technology was imported from a place yet to be identified, or originated from Oldowan toolmakers in the area.

In either case, the scientists wrote, “the Acheulean did not accompany the first human dispersal from Africa, despite being available at the time.”

Hominids thought to be Homo erectus — or possibly Homo habilis, an earlier group — were then living in what is now the country of Georgia. Their tools were Oldowan. So the archaeologists and geologists concluded that there may have been multiple groups of hominids “distinguished by separate stone-tool-making behaviors and dispersal strategies” co-existing in Africa 1.76 million years ago.

Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York who was not involved in the research, said rumors of much earlier Acheulean finds had been circulating for a long time, “and now we have it, and the evidence is well documented.”

The new find “is bound to open up the debate about the relationship between the appearance of the Acheulean and that of early African Homo erectus, the earliest hominid known to have basically modern human body proportions,” Dr. Tattersall said. It is thought that erectus evolved about two million years ago.

Although the authors suggested the possibility that more than one kind of hominid was making tools at the site, Dr. Tattersall said it was also conceivable that the Acheulean culture was born within the Oldowan. “After all, any cultural innovation has to be invented within some existing tradition,” he noted. “And it was typically the case that old Paleolithic technologies survived for long periods alongside the new.”

Dr. Tattersall said he found it odd that “the Acheulean evidently didn’t catch on widely for several hundred thousand years after it was invented, possibly for the same reasons — whatever they are — that it took a really long time to be adopted at all widely in Eurasia, even as African groups were evidently migrating out.”

Eric Delson, a paleoanthropologist at Lehman College of the City University of New York, said he was disappointed in the few pictures of the stone tools that were published with the report, describing them as “rather rough.” He said the tools “in some ways appeared to be intermediate between Oldowan and Acheulean tools, which might be expected for the first Acheulean artifacts.”

Nonetheless, Dr. Delson said, the new date for the earliest known Acheulean “moves it back closer to the earliest Homo erectus and supports — but does not prove — the widespread view that erectus made the Acheulean, at least at the beginning.”

But as he reviewed the research’s implications for the role of Homo erectus in the spread of early humans, Dr. Delson sounded the familiar lament of paleoanthropology: “Each new find raises about as many questions as it helps to resolve.”