The skeleton was quietly flown out of Ethiopia earlier this week for the U.S. tour.
Paleontologist Richard Leakey joined other experts in criticizing what some see as a gamble with one of the world's most famous fossils. The Smithsonian Institution also has objected to the tour, and the secretive manner in which the remains were sent abroad has raised eyebrows in Ethiopia, where Lucy has been displayed to the public only twice.
"It's a form of prostitution, it's gross exploitation of the ancestors of humanity and it should not be permitted," Leakey told The Associated Press in an interview at his office in Nairobi.
Ethiopian officials could not immediately be reached for comment, but have said proceeds from the tour would be used to upgrade museums in one of the world's poorest countries.
Dirk Van Tuerenhout, the curator of anthropology at the Houston Museum of Natural Science, where Lucy will be on display from Aug. 31 to April 20, said his museum would treat the relic with "the greatest respect and sense of protection — something we in the museum world do all the time."
"On the one hand, I would say we definitely share the concern that people have to safeguard fossils like Lucy, or for that matter any other fossils," Van Tuerenhout said. "Where we part company, in a sense, is the decision that was made to allow her to travel."
He emphasized the decision to allow Lucy to travel abroad was made by the Ethiopian government, and that Houston was honored by its selection.
Van Tuerenhout also noted the exhibit's story line was broader than just Lucy and offers other educational aspects.
"We are definitely going to be able, with Lucy's presence, to tell the story of Ethiopia — not only the prehistoric part, but also the historic part," he said. "This is one of those exhibits that covers quite a lot of history."
Lucy, the fossilized partial skeleton of what was once a 3 1/2-foot-tall adult of an ape-man species, was discovered in 1974 in the remote, desert-like Afar region in northeastern Ethiopia. Lucy is classified as an Australopithecus afarensis, which lived in Africa between about 3 million to 4 million years ago, and is the earliest known hominid.
The State Department approved the exhibit for temporary importation into the U.S., saying that display of Lucy and the other artifacts is in the national interest because of their "cultural significance."
Stops beyond Houston have yet to be finalized, but Ethiopian officials have said they include New York, Denver and Chicago.
Leakey said the skeleton will almost certainly get damaged.
"These specimens will get damaged no matter how careful you are and every time she is moved there is a risk," he said. "A specimen that is that precious and unique shouldn't be exposed to the threats of damage by travel."
He also said keeping Lucy in Ethiopia would lure tourists to the country.
"The point is, what is the benefit of taking one of the most iconic examples of the human story from Africa to parade it around in second-level museums in the United States?" he said.
Leakey is one of the world's most renowned paleontologists. His team unearthed the bones of Turkana Boy — the most complete skeleton of a prehistoric human ever found — in the desolate, far northern reaches of Kenya in 1984.
He is also a conservationist credited with helping end the slaughter of elephants in Kenya during the 1980s.
"The point is, what is the benefit of taking one of the most iconic examples of the human story from Africa to parade it around in second-level museums in the United States?"
-Paleontologist Richard Leakey
No Goodbyes for Famous Lucy