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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

View a reconstruction from fossil casts of a Neanderthal at the Dolan DNA Learning Center

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