New Clue on Which Came First, Tools or Better Diets
By JOHN NOBLE WILFORD

Published: October 21, 2003

The discovery in Ethiopia of stone tools almost 2.6 million years old
could help resolve a debate over human brain size, diet and toolmaking.

On a hillside in the badlands of Ethiopia, an ancestral home of the
human family, an international team of scientists has uncovered the
earliest known stone tools to be found mixed with fragments of
fossilized animal bones. The scientists think the material, almost 2.6
million years old, is the strongest evidence yet that the primal
technology was used to butcher animal carcasses for meat and marrow.

The discovery could go a long way toward resolving a debate in
paleoanthropology: which came first, a significant advance in the brain
that enabled human ancestors to make tools, or the toolmaking ability
that led to an enriched diet and then an evolutionary change in the
brain?

"I believe the use of stone tools came first and the larger brain came
later with a more substantial meat diet," Dr. Sileshi Semaw, the leader
of the discovery team, said last week by telephone.

The findings are described in the current issue of The Journal of Human
Evolution. Dr. Semaw, principal author of the report, is a
paleoanthropologist who is a research associate at the Center for
Research Into the Anthropological Foundations of Technology at Indiana
University.

The age of the stone tools was no surprise, the researchers said.
Working in the same region a decade ago, Dr. Semaw found similar cobbles
flaked for use in scraping and cutting at sites of about the same age.
The cobbles were hailed as the earliest known artifacts created by
distant human relatives, known as hominids.

Nor was it startling to find animal bones with cut marks, presumably
made by the sharp edges of butchering tools. Similar fossilized bones
with stone-tool cut marks had been excavated at a site 50 miles away,
but without any associated artifacts. Never before, the researchers
said, had stone artifacts and animal bones been found together at a
single site from this early time in human evolution.

In the journal report, Dr. Semaw's group said the discovery near the
bank of a branch of the Gona River, in the Afar region of Ethiopia, had
provided "the oldest known archaeologically documented associations
between artifacts and broken faunal elements," or animal bones.

Another member of the team, Dr. Michael J. Rogers of Southern
Connecticut State University in New Haven, said in an interview that the
stone tools and the animal bones, probably from ancestors of wildebeests
and zebras, had been unquestionably associated with each other.

"What's important," Dr. Rogers said, "is that this suggests that early
stone-tool use was responsible for much of the expansion of hominid diet
from mostly plants to more meat and marrow."

Dr. Rogers, a paleoanthropologist, came upon the most revealing site
three years ago while searching the arid hills for fossils or artifacts.
Several sharp flakes of rock caught his eye. They were no more than an
inch or two long, he said, and they were different from any other rock
on the surface. They looked as if they had recently eroded out of the
hill.

"We got a little bit excited," Dr. Rogers said, and soon he and
colleagues began excavating and uncovered some of the cobbles from which
the flakes had been broken. Then they began finding bones, including rib
and limb fragments. At another site a few yards away, discovered by Dr.
Jay Quade of the University of Arizona, the excavators found several
bones with distinct cut marks.

The quality of the tool workmanship impressed the researchers. "The
flakes are amazingly well struck and look much the same as tools made a
million years later," Dr. Rogers said.

No hominid fossil bones have been found at the sites, so it is
impossible to tell who the toolmakers were. The researchers said that
they were probably members of the 2.5-million-year-old species named
Australopithecus garhi, which lived in Ethiopia and was identified in
1999 by Dr. Tim D. White of the University of California at Berkeley.

Dr. White said the new research provided more evidence that "a dietary
and technological threshold had been crossed" by 2.6 million years ago.

http://www.nytimes.com/2003/10/21/science/21TOOL.html