SCIENCE, Vol. 263, 2/4/94, p. 611-612

      Did Early Humans Reach Siberia 500,000 Years Ago?
                     by Virginia Morell

Twelve years ago, while excavating in northern Siberia,
archeologists Yuri A. Mochanov and his wife, Svetlana
Fedoseeva of the Russian Academy of Sciences, came upon a
few unprepossessing rocks. That might not sound like much,
but to Mochanov those rocks looked like very early stone
tools, tools with which he could construct a new path for
human evolution--a path that began in the cold north, rather
than on the warm plains of Africa as almost all his col
leagues believed.
   To those colleagues, however, the find simply looked like
unprepossessing rocks. But now, thanks to a reexamination of
the material and high-tech geologic dating methods, those
skeptics are beginning to think that while Mochanov may not
rewrite prehistory completely, he may be able to revise a
chapter about Homo erectus, a human ancestor who lived from
approximately 1.7 million years to 200,000 years ago.
   The rocks in question were discovered as the two Russians
unearthed a 3000 to 4000-year-old tomb at the Diring-Yuriakh
(Deep Creek) site on the Lena River. Below the tomb they
spotted a scattering of crudely shaped stone tools. Mochanov
and Fedoseeva had seen similar tools before, but they came
from East Africa, and they were 2.4 million years old, the
earliest known tools made by human ancestors. At the time,
it was thought that the earliest human occupation of Siberia
took place 20,000 to 30,000 years ago. "I was stunned,"
Mochanov recalls. "Nothing like this had ever been found in
Siberia and I thought, 'This is impossible.'"
   Over the next several years, his incredulity vanished as
he amassed more than 4000 quartzite artifacts, primarily
anvil stones, flakes, and choppers. And based on the simi-
larities between the Siberian and African tools, as well as
preliminary studies that dated the site at 3 million years
of age, Mochanov proposed a northern Russian genesis for
humanity, beginning at that time.
   That didn't sit at all well with his colleagues, who
thought Diring's geology and dates were far too shaky to
hold up a theory that contradicted the abundant and well-
accepted evidence pointing to African origins. To make
matters worse for Mochanov, few archeologists accepted the
artifacts as tools, believing instead that the quartzite
cobbles could have been chipped by some geological process.
"The site needs to be looked at with a properly jaundiced
eye," says William Kimbel, a paleoanthropologist at
the Institute for Human Origins in Berkeley. Lately,
however, the jaundiced eyes are beginning to open wide. For
the past month, Mochanov and Fedoseeva have been
barnstorming the United States, showing their artifacts to
experts at Oregon State and the Smithsonian Institution,
among other places. Many of these scientists had never seen
the tools firsthand and many of them are impressed. And some
new dating studies using a technique called thermolumines-
cence (TL) suggest that the artifacts may be at least
500,000 years old. That's a far cry from Mochanov's original
claim, but still old enough to make former skeptics sit up
and take notice.
   "I would have been excited if the tools were only 50,000
years old," says one recent convert, Dennis Stanford,
chairman of the anthropology department at the Smithsonian.
"But 500,000 years opens up a Pandora's box of
possibilities." The date is within the time period of
erectus, and one of those possibilities is that erectus
could have pushed much further north than previously
believed (the next most northern erectus site is 2500
kilometers south of Diring, in China). It's also possible
that early humans erectus descendants could have pushed
from Siberia through Beringia and into America long before
the currently accepted colonization date of around 14,000
years ago (see Report in this issue, p. 660).
   The key to this Pandora's box is an ongoing series of
studies by Michael Waters, a geoarcheologist at Texas A & M
University, whom the National Geographic Society sent to
Diring to help Mochanov evaluate the site. Waters confirmed
that the artifacts lay in windblown quartzite sand deposits,
which are well-suited for TL dating. This technique measures
time by counting the number of stray electrons trapped in
minerals, an entrapment that takes place at a steady rate.
Although a relatively new--and still controversial--method,
TL is the only game in town at sites such as Diring, where
there are neither fossilized animal remains that might be
correlated with those from another securely dated site nor
volcanic ash deposits for potassium-argon dating. The
sediment samples Waters collected at Diring were dated by
geochronologists Steve Forman and James Pierson at Ohio
State University.
   But the TL dates are not the only evidence that is
beginning to shift the consensus on the Diring site. It's
also the tools themselves. Mochanov has unearthed 33 areas
marked by anvil stones, quartzite flakes, and, in some
cases, the quartzite cobble from which the flakes were
chipped; often the flakes can be refitted onto the cobbles.
These elements, all definitive signs of human activity,
convinced Rick Potts, a Smithsonian archeologist and expert
on early tools, that he was looking at hominid handiwork and
not just randomly broken rocks.
   "The Diring artifacts are very, very simple one-step
tools," explains Potts, who had only heard sketchy details
about the site until Mochanov's visit. "All they were basi-
cally doing was smashing one rock with another, just to get
a few pieces off That's why the tools look very rough and
crude--I think Diring was their quarry site." Perhaps, Potts
speculates, the inhabitants broke the rocks into smaller
pieces that were easier to hold, then carried these to other
sites where they may have fashioned more elaborate tools.
   If human ancestors did live at a site that's just below
the Arctic Circle, "it implies a range of behaviors and
adaptations that we have never given Homo erectus credit
for, from making mitts and boots, to controlling fire and
having winter survival strategies," says Waters. Until
Mochanov's discovery, no one had found any signs of erectus
any farther north in Asia than Zhoukoudian, the huge
limestone cave in central China used by the famous "Peking
Man" nearly 500,000 years ago. "What Mochanov may be seeing
at Diring is part of a south-north migration pattern,"
suggests Robert E. Ackerman, an archeologist at Washington
State University in Pullman, who visited Diring 4 years ago.
"Perhaps this is part of a movement north out of China
during a warming trend." However, scientists have little
data about the paleoclimate of Siberia, and there is as yet
no way of knowing how cold or warm the Diring peoples'
environment really was. Waters suspects the site is at a
high enough latitude that, even during a warm interglacial
period, the climate would be similar to the climate today--
and that can be chilly indeed. At Yakutsk, just north of
Diring, the mercury falls as low as -45 degrees Farenheit in
January.
   The ability to cope with cold at that time in human
prehistory also figures in the peopling of the Americas.
"For those who've wanted to see an earlier date for the
peopling of the Americas this [500,000-year-old] date is a
cause for celebration," says Stanford. He notes that critics
have always argued that people did not have sophisticated
enough technologies to survive in the Arctic until very
recently. "But if people were dealing with the cold that far
north in Siberia 500,000 years ago, then a little bitty ice
age like the Wisconsin isn't going to stop you from getting
to America," he says.
   No one, however, is going to push Diring as evidence for
early American pilgrims until the twin issues of the
environment and dating are much more settled. Mochanov has
found no erectus fossils, which would clinch the case for
the site as an erectus habitat, or animal fossils, which
would go a long way toward clearing up questions about just
how cold it was back then. "Those are the kinds of questions
that have to be answered before we can explain the Diring
peoples' behavior," says Potts. "We need to know what the
survival strategies were of other animals in the area. If
they were all cold weather-adapted, then you'd have to say
these hominids made a real breakthrough--one that no others
were doing."
   As for the 500,000-year-old date, there is still at least
one scientist who is dissatisfied with it--Mochanov. He
doesn't think it is old enough, and he is still sticking to
his 3-million-year-old claim. "That is preliminary work," he
says of the TL date, adding that he wants to wait for
Waters' and Forman's final report, which is due by the end
of this summer. "If we find we have a mistake [with the
earlier date]," says Mochanov, "then we will correct it." At
least his North American colleagues have already begun to
correct their notion that Diring is a dud.