History Forum / General / Archaeology / September 2007

Hard to believe this one, but the "back to Africa" movement seems to
have occurred a least 1.77 million years ago if this account is
accurate. Home E and his predecessors seem to have made it as far as
Sakartvelo (Georgia). The description makes Piltdown Man sound like
the norm.

Science News Online

Week of Sept. 22, 2007; Vol. 172, No. 12
Walking Small: Humanlike legs took Homo out of Africa

Bruce Bower

The earliest known human ancestors that trekked from Africa into Asia
possessed legs, feet, and spines much like ours, even as they sported
relatively apelike arms and small brains, according to an analysis of
1.77-million-year-old fossils unearthed in the central Asian nation of
Georgia.

A team led by David Lordkipanidze of the Georgian National Museum in
Tbilisi recovered 33 lower-body bones from at least three adults and
one teenager at a site called Dmanisi. The researchers had previously
found four skulls and four lower jaws, as well as simple stone tools,
in the same sediment (SN: 5/13/00, p. 308). In several cases, skull
and lower-body remains come from the same individual.

The researchers classify these ancient finds as early Homo. The
fossils might be from an early form of Homo erectus that left eastern
Africa for the Asian hinterlands, but a definitive species identity
remains unclear, Lordkipanidze cautions. A description of the new
finds appears in the Sept. 20 Nature.

"The Dmanisi individuals weren't the first hominids [fossil ancestors
of humans] to leave Africa," Lordkipanidze says. "They must have had
more-primitive ancestors that passed through the Near East before
reaching Georgia."

An intriguing mosaic of anatomical traits characterizes the Dmanisi
folk. Their legs and spines closely resemble those of modern humans.
In particular, Dmanisi leg and foot bones would have efficiently
supported long-distance walking and running, the scientists assert.

However, the arms of Dmanisi hominids appear more like those of
australopithecines, an earlier line of hominids. For instance, unlike
people, the new specimens have upper arms that are straight rather
than slightly curved, their shoulders are relatively narrow, and their
palms are oriented forward rather than inward.

Moreover, the Dmanisi individuals are small compared with the oldest
known African H. erectus. That specimen, a 1.5-million-year-old
skeleton of a well-developed, roughly 10-year-old boy, stood tall at
between 151 and 169 centimeters and weighed as much as 70 kilograms.
At Dmanisi, adults reached estimated heights of between 145 and 166 cm
and weighed between 40 and 50 kg.

Such estimates coincide with Dmanisi brain volumes that were one-half
to two-thirds the size of modern human brains.

The Dmanisi fossils and early African H. erectus remains probably
represent separate populations of a species that evolved variations of
a common body plan as members settled different habitats, suggests
anthropologist Daniel E. Lieberman of Harvard University in a comment
published with the new report.

If the Dmanisi remains indeed belong to early H. erectus, members of
that species must have returned to Africa and evolved into a larger,
more modern-looking form by 1.5 million years ago, remarks
anthropologist William L. Jungers of Stony Brook (N.Y.) University
Medical Center. In his view, the Dmanisi foot bones were built for
long-distance walking but show no convincing sign of having supported
a fully modern running ability.

Jungers adds that the australopithecine-like arm traits in Dmanisi
individuals also appear in Homo floresiensis, Indonesian ancestors
that some researchers regard as modern humans with a developmental
disorder (SN: 11/18/06, p. 330). Jungers, however, contends that H.
floresiensis was a separate species that preserved some primitive
skeletal features, just as H. erectus did at Dmanisi.

References:

Lieberman, D.E. 2007. Homing in on early Homo. Nature 449(Sept. 20):
291-292.

Lordkipanidze, D., et al. 2007. Postcranial evidence from early Homo
from Dmanisi, Georgia. Nature 449(Sept. 20):305-310. Abstract
available at http://dx.doi.org/10.1038/nature06134.

Further Readings:

Bower, B. 2006. Evolution's mystery woman. Science News 170(Nov. 18):
330-331. Available to subscribers at http://www.sciencenews.org/articles/20061118/bob9.asp.

______. 2000. Fossils hint at who left Africa first. Science News
157(May 13):308. Available to subscribers at
http://www.sciencenews.org/articles/20000513/fob1.asp.

Sources:

William L. Jungers
Department of Anatomical Sciences
Stony Brook University Medical Center
Stony Brook, NY 11794-8081

Daniel E. Lieberman
Department of Anthropology
Harvard University
Cambridge, MA 02138

David Lordkipanidze
Georgian National Museum
3 Purtseladze st.
0105 Tbilisi
Georgia

http://www.sciencenews.org/articles/20070922/fob1.asp