NEWS & ANALYSIS
www.sciencemag.org SCIENCE VOL 342 18 OCTOBER 2013 297
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NEWS & ANALYSIS
It was the ultimate birthday gift. On his 42nd
birthday, 5 August 2005, paleoanthropolo-
gist David Lordkipanidze was presented
with the most complete early Homo skull
ever found, freshly uncovered at his site of
Dmanisi, Georgia. As paleontologists gently
brushed dirt off its face, they saw strange,
primitive features, unexpected in even an
early member of our genus: a protruding,
apelike upper jaw, and a tiny braincase. One
scientist joked that you should put it back
in the ground, Lordkipanidze recalls.
Instead, Lordkipanidze and an interna-
tional team spent 8 years studying the fossil,
which they describe on page 326. Dating back
to about 1.8 million years ago, the spectacu-
lar skull includes delicate parts of the face,
rare in other nds, making it the worlds rst
completely preserved adult hominid skull
of such antiquity, they write. Combined with
skulls found earlier at Dmanisi, it also sug-
gests that ancient individuals from the same
time and place were very different from each
other but still members of one speciesan
idea that has implications for the perplex-
ing patchwork of Homo fossils
found in Africa.
The skull is undoubtedly
one of the most important ever
discovered, says paleoanthro-
pologist Ian Tattersall of the
American Museum of Natural
History in New York City. An
iconic fossil, proclaims Tim White, a paleo-
anthropologist at the University of California,
Berkeley. It will stand out for a long time.
Over the past 20 years, Lordkipanidze
and his colleagues have unearthed skulls and
skeletal bones from at least ve individuals
from Dmanisi, a site that preserves the old-
est human fossils found outside of Africa.
These early humans used crude stone tools,
probably for butchering animals, and lived
near a river, a busy watering hole, says geo-
archaeologist Reid Ferring of the University
of North Texas, Denton. Ferring used argon
isotopes to date the site to 1.77 million to
1.85 million years ago, showing that Homo
had expanded into Asia not long after
the genus appeared in Africa.
At that time about 18% of the sites
animal bones belonged to carnivores,
including fierce saber-toothed cats
and an extinct giant cheetah. Con-
frontations with these beasts would
have been commonand danger-
ous. All five individuals were found
in underground dens where carnivores
had probably dragged their carcasses.
Ferring thinks the skeletons were all
deposited within a couple centuries, at
most, after which the dens collapsed.
This carnivores cache has pro-
duced new fossils season after
season. The massive lower jaw of
the new skull was found back in
2000, and Lordkipanidze and oth-
ers had expected to unearth a huge
cranium to go with it. Instead they
found the cranium of an older man
with arthritis in his jaw, worn front
teeth probably used as a gripping tooland
a small brain of only 546 cubic centime-
ters. Thats within range of an earlier human
ancestor, Australopithecus, whose brains
averaged 450 cm3, compared with 1350
cm3 for modern humans, notes co-author
Christoph Zollikofer, a neurobiologist at the
University of Zurich in Switzerland. This
con rms that our ancestors didnt need big
brains to get out of Africa.
When the researchers attached the lower
jaw to the new cranium, designated Skull 5,
the lower face bones jutted out more like an
Australopithecus. This is, in essence, a very
primitive face, says co-author Yoel Rak of
Tel Aviv University in Israel.
Yet its clearly Homo, many research-
ers agree. The skulls vertically oriented
upper face and the shape of the braincase
distinguish it from Australopithecus. Skel-
etal bones found with the skulls, including
Skull 5, show that although these humans
were short in stature, they had modern body
proportions and could walk long distances
(Science, 21 September 2007, p. 1664).
But what species of Homo is it? Some
fossils previously discovered at Dmanisi
seemed to have links to H. erectus. But when
the big lower jaw was found in 2000, some
researchers suggested it belonged to a new
species they called Homo georgicus.
With the discovery of the new, fth skull,
Stunning Skull Gives a Fresh Portrait of Early Humans
PALEOANTHROPOLOGY
Onlinesciencemag.org
See slideshow for images of the new
skull (http://scim.ag/slide_6156).
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Azerbaijan
Armenia
I ran
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Dmaninsi
M e d i t e r r a n e a n S e a
B l a c k S e a
Putting their heads together. Researchers think that all ve of
these skulls from Dmanisi belong in one species. Skull 5 is on the
right.
Published by AAAS
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18 OCTOBER 2013 VOL 342 SCIENCE www.sciencemag.org 298
NEWS&ANALYSIS
A Prize for Molecular ModelingYouve seen the modelsmolecules
rep-
resented as balls connected by sticks, often
pared down to a few lines on paper. Useful as
they are to chemists, they leave out something
essential: motion, the intricate dance of elec-
trons and atomic nuclei breaking and fusing
bonds as they undergo reactions. That dance
is the heart of chemistry. Last weeks Nobel
Prize in chemistry was awarded to three U.S.-
based scientists for developing computer
models that reveal how pro-
teins and other compounds
perform it.
All three of this years
chemistry laureates are nat-
uralized U.S. citizens. Mar-
tin Karplus of Harvard Uni-
versity and the University
of Strasbourg in France was
born in 1930 in Vienna and
moved to the United States
just before the outbreak of
World War II. Michael Lev-
itt of Stanford Universi-
tys School of Medicine in
Palo Alto, Cal ifornia, was
born in Pretoria in 1947,
and today is a British, U.S., and Israeli cit-
izen. And Arieh Warshel of the University
of Southern California in Los Angeles was
born in 1940 in Kibbutz Sde-Nahum, Israel,
and still holds Israeli citizenship.
More than 40 years ago, the three pio-
neered new tools for fusing two disparate
world views among chemists working to
simulate molecules. One of them, grounded
in classical Newtonian physics, treated mole-
cules as collections of atomic balls connected
by springlike bonds. Because this approach
was mathematically tractable for large num-
bers of atoms, it enabled researchers to sim-
ulate proteins and other large molecules. In
1969, Levitt and Warshel, then both at the
Weizmann Institute of Science in Rehovot,
Israel, designed a ball-and-spring com-
puter model that could track how proteins
and other large biomolecules oscillate and
twist. But it couldnt calculate the changes
in energy involved when chemicals react and
form new molecules.
Meanwhile, at Har-
vard, Karplus was deeply
enmeshed in the second
approach to simulation,
called quantum chem-
istry. It was far better at
simulating the motion of
the electrons and atomic
nuclei involved in reac-
tions. But it was so com-
putationally demanding
that it was useful only in
solving the behavior of
small molecules.
Trying to bring the
quantum and classical CRE
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the researchers had to confront head-on the
variation among all ve. Age and sex prob-
ably account for much of it: The skulls
are thought to have belonged to an elderly
toothless male, two mature males, a young
female, and an adolescent of unknown sex.
This broad sample from one place and a
short span of time is what makes Dmanisi an
exceptional site, White says. By analyzing
the skull shapes with 3D computer-based
methods, the researchers found that the
range of variation in the group at Dmanisi
was no greater than within living humans
or chimps. The team concluded that all ve
skulls belong to a single, variable species
Putting all ve skulls into a single spe-
cies still left the problem of what to call
it. The team squabbled at rst. Looking at
particular traits, they found that the upper
jaw of Skull 5 most closely resembles the
oldest fossil proposed as Homoa 2.3-
million-year-old jaw from Ethiopia tenta-
tively assigned to H. habilis. But Skull 5 also
shares key features with H. erectus, such as
thick brow ridges. In the end, the team set-
tled on the cumbersome moniker of Homo
erectus ergaster georgicus, which recog-
nizes the skull as an earlier Georgian form
of H. erectus. But they all prefer to call their
nds early Homo.
The skull shape analysis and classical
trait analysis, done by Zollikofer and his Zur-
ich colleague Marcia Ponce de Len, also
showed that the skulls were as variable as
African fossils traditionally classi ed in three
different speciesH. erectus, H. habilis, and
H. rudolfensis. If the Dmanisi fossils had been
found in separate places in Africa, they could
have been called separate species, Ponce de
Len says. Lumping them all into H. erectus
suggests that the early Homo fossils in Africa
may also belong to that same, single lineage.
That controversial idea is setting off a
small bomb in the field, says co-author
Philip Rightmire of Harvard University.
Tattersall thinks Dmanisi could include more
than one species, and that Skull 5 represents a
new species. Paleoanthropologist Ron Clarke
of the University of the Witwatersrand in
Johannesburg, South Africa, counters that
Skull 5 looks to me like Homo habilis. And
while paleontologist Fred Spoor of the Max
Planck Institute for Evolutionary Anthro-
pology in Leipzig, Germany, thinks it sen-
sible to call Skull 5 H. erectus, he balks at
the notion that fossils in Africa all belong in
H. erectus, too, arguing that the teams analy-
ses cant delineate diagnostic differences in
skull shape.
Whatever Skull 5s speci c identity, Spoor
agrees that it is a fantastic, terri c speci-
men. Says White: No matter what you call
it, this skull and the others from Dmanisi are
some of the best evidence we have about how,
where, when, and why humans evolved.
ANN GIBBONS
Molecule and Market Studies Capture Nobel Laurels
PR IZES
Lowbrow. This artists reconstruction shows the new skulls small
brain and protruding jaw.
NOBEL PRIZE 2013NOBEL PRIZE 201
CHEMISTRY
MICHAEL LEVITT ARIEH WARSHELMARTIN KARPLUS
Published by AAAS
