Lucy's bones have never been exhibited abroad. They are kept in a vault at the Ethiopian Natural History Museum in the capital city of Adis Abeba (Addis Ababa).
"Due to her completeness as a 3.2-million-year-old skeleton, Lucy is a truly exceptional, irreplaceable discovery," said Rick Potts, director of the Smithsonian's Human Origins Program.
"Any risk of damage or removal from scientific study, especially when exact replicas of the fossils are indistinguishable for display purposes, seems unnecessary and, in this particular case, not well conceived."
Potts says such fossils should be removed from their vaults only for the most compelling scientific reasons.
"The Lucy fossil is quite fragile, and there is always the possibility of damage if it were to be moved," he said.
But Bartsch, the Houston museum president, says international museums routinely transport such objects for public display.
The museum is currently showcasing the original U.S. Declaration of Independence, on loan from the American Philosophical Society based in Philadelphia, Pennsylvania.
"[We are] fully aware of the enormous responsibility that comes with developing and managing this exhibition in partnership with the Ethiopian government," Bartsch said.
"We will take every precaution to ensure that no object will be lost or damaged."
Ian Tattersall, curator of the department of anthropology at the American Museum of Natural History in New York City, says the tour may not be in the best interest of science.
"While I can see a very positive side to a single showing of Lucy in Houston, I think a protracted tour would be very undesirable," Tattersall said, emphasizing that this is his opinion and not an official position of the museum.
"It would unacceptably increase the risk to the specimen, and even in the best of scenarios would take it out of the scientific arena for an extended period," he said.
"It is active science that gives Lucy her true value."
Potts, of the Smithsonian, argues that the Lucy tour is designed to benefit the Ethiopian government, which negotiated the deal, and not the National Museum of Ethiopia, which is responsible for the care of the invaluable fossil.
However, John Kappelman, a professor of physical anthropology at the University of Texas at Austin, says bringing Lucy to the United States is an opportunity to do scientific investigations of the specimen that can otherwise not be done.
His university has proposed using a high-resolution x-ray CT (computed tomography) facility on its campus to scan and image Lucy's bones.
At 3 feet, 6 inches (just over a meter) tall and weighing about 62 pounds (28 kilograms), Lucy almost certainly stood upright and walked on two feet.
But scientists differ on how she moved and whether she would have retained apelike climbing abilities.
"Some of the things that have never been studied on Lucy are her trabecular bone [a spongy type of bone found at the ends of long bones], which informs us about her mode of locomotion—how she used her arms, how she used her legs," he said.
"We can do that [with this CT scan] on a very fine level." (Related news: "King Tut Not Murdered Violently, CT Scans Show" [March 8, 2005].)
Kappelman also takes issue with scientists who have accused organizers of using the fossils as a tourist attraction.
"There are lots of informed people out there who would love to see this specimen," he said. "The term 'tourist' is a very unfair way of categorizing them."
He says Lucy has the potential to educate people about human evolution like no other single specimen in the world could.
"I think it's going to get people excited about the science in a way that the King Tut exhibit in the United States 30 years ago got people excited about Egypt," Kappelman said.
Although no details about the tour have been finalized, Bartsch, the Houston museum president, says finding other museums to host Lucy will not be a problem.
"In the last few days," he said, "we have had inquiries from more than a dozen prominent, well-respected institutions, each of whom expressed very strong interest in hosting the exhibition."
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