By Paul Rincon
BBC News Online science staff
The legal battle over the ancient bones of Kennewick Man has been won by the scientists, but they now face a new wrangle over access to the remains.
The remains could reveal secrets of the settlement of the Americas
The 9,300-year-old skeleton is among the most complete specimens of its period known from the Americas.
Four Native American tribes that sought to re-bury the bones have announced they will not be taking their fight to the US Supreme Court.
But they still regard the skeleton as an ancestor and call it "ancient one".
The Nez Perce, Umatilla, Yakama and Colville tribes filed a claim to the skeleton shortly after it was unearthed on 31 July, 1996, on a wide bank of the Columbia river at Kennewick in Washington State.
However, they were quickly challenged by scientists who said the skeleton could provide valuable information about the early settling of the Americas.
In February, the coalition of tribes lost their legal fight in the federal courts to scientists who want to study the remains.
The San Francisco-based Ninth Circuit Court of Appeals ruled that it was impossible to establish a relationship between the Indian tribes and "Kennewick Man".
An attempt to have the decision reviewed by a panel of judges was also rejected.
The defendants had the option to continue the fight in the US Supreme Court. But neither the tribes nor the US Justice Department filed an appeal to America's highest court by the Monday deadline.
However, legal representatives for the scientists are still locked in discussions with the US Justice Department over what the researchers are allowed to do with the bones.
Attorney for the scientists Alan L Schneider told BBC News Online: "We feel that they are improperly interjecting themselves into the purpose for which we can study the skeleton and the types of studies that would be appropriate to achieve the objectives."
The government has said that it would not permit any chemical or invasive testing on the bones. This would scupper any further attempts to obtain DNA samples from Kennewick Man.
The discussions are also likely to cover the question of how access to the remains is controlled.
"They're saying you have to restrict your studies and only a couple of people can go in and look at it and that sort of thing," Professor Robson Bonnichsen, one of the lead scientists, told BBC News Online.
The plaintiffs are also concerned by suggestions the bones may have deteriorated in the eight years since they were pulled from the sediment.
"The government has now come up with all kinds of concerns - that the skeleton is in such poor condition. The condition's changed under their watch because everyone said it was in great condition when it came in," explained Professor Bonnichsen.
"We know that the number of pieces of skeleton have grown since they've been there lying in the cabinet," he added.
Three tribes decided not to appeal the case before the weekend. The Umatilla held out to the deadline, but said in a statement on Monday that it would not proceed with the case any further.
"The decision was based on the availability of financial resources, the uncertainty of whether the Supreme Court would even hear the case, and the risk that an unfavourable Court decision could become law," the statement read.
It added that the Umatilla's board of trustees would begin working with other Native American tribes on a strategy to amend the Native American Graves Protection and Repatriation Act (Nagpra), the law enacted in 1990 to protect tribal burials.
"Nagpra needs to be strengthened so that it fulfils Congress' original intent, which was to protect tribal burials and return sacred items to the tribes," said Armand Minthorn, Umatilla board of trustees member.
The bones of Kennewick Man are currently held at the Burke Museum in Seattle.