New Neanderthal knowledge

Web Extra Thursday, Mar. 17, 2005
New Neanderthal knowledge

Although the classic perception of Neanderthals, first
discovered in 1856, is that they are primitive, slouched-over
versions of modern humans, they are actually an entirely
separate subspecies from Homo sapiens. Recent studies are,
however, making links — both genetic and morphologic — between
Neanderthals and modern people, thus helping to put together the
pieces of the human evolution puzzle.

Anthropologists G.J. Sawyer from the American Museum of Natural
History and Blaine Maley of Washington University in St. Louis,
Mo., undertook the task of articulating a Neanderthal skeleton.
Starting with a well-preserved and virtually complete specimen
known as La Ferrassie 1, found in France in 1909, Sawyer and
Maley replaced missing bones, such as the pelvis and vertebral
column, with Neanderthal bones found in Europe. Together, the
various body parts formed a complete skeleton.

The resulting articulated skeleton, whose photos were published
in the March 11 online version of The Anatomical Record Part B:
The New Anatomist, are helping researchers visually quantify the
differences between the morphology of modern humans and
Neanderthals. Body characteristics, Maley says, are the
definitive approach to classifying organisms taxonomically.

Most of the distinct body characteristics, such as the skull,
arms and leg bones, are generally comparable to modern humans,
Maley says. "It is the suite" of characteristics together that
"allows one to really differentiate the two groups." For
instance, there is an appreciative difference in the shape of
the rib cage and the pelvic area, and this study also refutes
some of the previously suggested Neanderthal body types, such as
the slouched gorilla appearance with a barrel-shaped trunk.
Instead, Maley and colleagues suggest that the Neanderthal had a
bell-shaped torso.

Still, Maley says, it is not wise to "draw any conclusions based
on one composite skeleton." By excavating more complete
individual skeletons, "we will garner a better understanding of
… just how accurate our reconstruction is," he says.

But morphology is not the only way to connect human ancestors
across time. Genetic research is showing some similarities
between modern humans and Neanderthals, notably in the amino
acid sequence of a protein secreted during bone growth, as
indicated by research published in the March 7 online edition of
Proceedings of the National Academy of Sciences.

Intact DNA sequences are not likely to survive preservation in
fossils, despite what is portrayed in Jurassic Park, says Peter
Hauschka, an associate professor at the Harvard School of
Medicine and Dental Medicine and one of the authors of the
study. Therefore, Hauschka and colleagues instead extracted the
oldest fossil hominid protein, called osteocalcin, from a
75,000-year-old Neanderthal fossil from Shanidar Cave in Iraq.

One of more than 30,000 proteins whose function is determined by
genomic DNA in hominids, osteocalcin is bound to the bone
mineral during bone formation, so it is more likely to be
preserved than DNA sequences. By isolating and extracting the
protein from the bone, the research team was able to compare
amino acid sequences across organisms to better understand
genetic mutations over time, Hauschka says.

The team compared the Neanderthal protein sequence to that of
chimpanzees, old world monkeys, orangutans, gorillas and modern
humans. "The sequence was the same" in Neanderthals and modern
humans, says Erik Trinkaus, a co-author of the study from the
department of anthropology at Washington University in St.
Louis, Mo., who provided the bone for the analysis.

Hauschka points out, however, that osteocalcin probably has
nothing to do with the physical appearance of a Neanderthal, as
it is only a component of bone. Therefore, although this
research opens many doors to the possibilities of understanding
human genetic evolution, it does not take away the need for
comprehensive morphological studies.

"The next step is to go back in time in the fossil record,"
Trinkaus says, to determine whether amino acid sequences have
remained the same throughout the species groups that his team
looked at, or whether the pattern evolved individually. Further
study will also help scientists to understand the evolutionary
relationships between living and extinct species.

Laura Stafford
geotimes.org