Skull Provides Signs of When Humans Left Africa

[Kala]

January 11, 2007
http://www.nytimes. Com/2007/ 01/11/science/ 11cnd-skull. Html?_r=1& oref=slogin

Skull Provides Signs of When Humans Left Africa
By JOHN NOBLE WILFORD

From a new analysis of a human skull discovered in
South Africa more than 50 years ago, scientists say
they have obtained the first fossil evidence
establishing the relatively recent time for the
dispersal of modern Homo sapiens out of Africa.

The migrants appeared to have arrived at their new
homes in Asia and Europe with the distinct and
unmodified heads of Africans.

An international team of researchers reported today
that the age of the South African skull, which they
dated at about 36,000 years old, coincided with the
age of and closely resembled the skulls of humans who
were then living in Europe and the far eastern parts
of Asia, even Australia.

The timing, the scientists and other experts said,
introduced independent evidence supporting
archaeological finds and recent genetic studies
showing that modern humans left sub-Saharan Africa for
Eurasia between 65,000 and 25,000 years ago, probably
closer to 45,000 to 35,000 years ago in Europe.

Until now, however, paleontologists had been
frustrated by the absence of fossils to test the
hypothesis of most geneticists that the people of
sub-Saharan Africa and in Eurasia at this time were
one and the same — modern humans. The human fossil
record in Africa from 70,000 to 15,000 years ago had
been virtually blank.

Some scientists, on the other hand, have contended
that the migration could have begun as early as
100,000 years ago and that in the intervening time,
contact with more archaic populations like the
Neanderthals could have produced recognizable changes
in what became the modern humans of Eurasia. But no
scientists in the migration controversy have disputed
that ancestors of the human species originated in
Africa.

In a report in Friday’s issue of the journal Science,
a research team led by Frederick E. Grine of Stony
Brook University in New York concluded that the South
African skull provided critical corroboration of the
archaeological and genetic evidence indicating that
humans in fully modern form originated in sub-Saharan
Africa and migrated, almost unchanged, to populate
Europe and Asia.

Dr. Grine and his colleagues said in an announcement
by Stony Brook that the skull was the first fossil
evidence “in agreement with the out-of-Africa theory,
which predicts that humans like those that inhabited
Eurasia should be found in sub-Saharan Africa around
36,000 years ago.”

Ted Goebel, an anthropologist at Texas A & M
University who was not connected to the research, said
the skull opened the way to important insights about
“the missing years of modern humans.”

Writing in an accompanying commentary in the journal,
Dr. Goebel said, “Here is the first skull of an adult
modern human from sub-Saharan Africa that dates to the
critical period, and one that can speak to the
relationship of early moderns from Africa and Europe.”

The new findings pivoted on fixing the skull’s age.
When it was uncovered in 1952 near the town of
Hofmeyr, South Africa, the cranium was almost complete
but the bone degraded. Not enough carbon remained for
scientists at the time to extract a radiocarbon date.

Using new technology, Richard Bailey and other
researchers at the University of Oxford, England,
measured the amount of radiation that had been
absorbed by sand grains that filled the braincase
since its burial. They calculated the yearly rate at
which radiation had collected in the sand and checked
this with data from a CT scan of the bone. In this
way, they determined that the Hofmeyr skull belonged
to a human who lived 36,000 years ago, plus or minus
3,000 years.

Another member of the team, Katerina Harvati of the
Max Planck Institute for Evolutionary Anthropology in
Leipzig, Germany, made a detailed examination of the
shapes, sizes and contours of all parts of the skull.
She compared these three-dimensional measurements with
those of early human skulls from Europe and with
skulls of living humans in Eurasia and southern
Africa, including the Khoe-San, commonly known as the
Bushmen.

Because the Bushmen are well represented in the more
recent archaeological record, Dr. Harvati said, they
were expected to bear a close resemblance to the
Hofmeyr skull. Instead, the skull was found to be
quite distinct from all recent Africans, including the
Bushmen, she said, and it has “a very close affinity”
with fossil specimens of Europeans living in the Upper
Paleolithic, the period best known for advanced stone
tools and cave art.

“Much to my amazement,” Dr. Grine said in an
interview, “the skull linked very closely with those
from Europe at the time and not with South African
remains 15,000 years on.”

Dr. Grine said these modern humans probably originated
in East Africa, which is rich in fossils of ancestors
of the species, and had then moved into Eurasia and
also south to the tip of Africa.

“It would be nice,” he conceded, “if we had more than
one specimen.”

Another report in Science described one of the
earliest occupation sites of modern humans in Europe,
at Kostenki on the Don River 250 miles south of
Moscow. Its stone and bone tools and a human figurine
appeared to have been made about 45,000 years ago,
perhaps a little earlier than human sites to the west
in Europe.

The lead author of the report was Michael Anikovich of
the Russian Academy of Sciences. John Hoffecker of the
University of Colorado, a team member, said the small
figurine may be “the oldest example of figurative art
ever discovered.”

Dr. Goebel said the new research archaeology, genetics
and the Hofmeyr skull should help explain when and how
modern humans leaving Africa spread out to different
environments, which, he added, “is one of the greatest
untold stories in the history of humankind.”