A US appeals court has given permission to scientists to study a 9,000-year-old skeleton - despite the objections of some Native American tribes.
"Kennewick Man" is a 9,000-year-old American
The bones were found by two teenagers near Kennewick, Washington, in 1996.
Native Americans want to bury what they call the remains of a distant relative, but scientists say the unusual features of the skeleton need further study.
Appeal judges ruled it was impossible to establish a relationship between the Indian tribes and "Kennewick Man".
US government agencies who are defendants in the case and claimants from the Umatilla, Yakama, Colville and Nez Perce tribes can still appeal. They could take the case to the Supreme Court or ask for a rehearing with the Court of Appeals.
On Wednesday, Judge Ronald M Gould wrote that the remains could only be considered Native American if they "bear some relationship to presently existing tribe or people or culture".
"It's a terrific decision; it's seven-and-a-half years coming. Of course we've got to wait and see whether the government is going to appeal it," Professor Robson Bonnichsen, one of the scientists who fought the case, told BBC News Online.
Because "limited studies to date" could not establish the link to modern peoples, the San Francisco-based Ninth Circuit Court of Appeals gave the green light to the scientists.
In the US, the Native American Graves Protection and Repatriation Act (Nagpra) has resulted in the handover of many artefacts and remains held in collections to claimants.
In a statement, the Confederated Tribes of the Umatilla Reservation, said "With this decision, we are concerned about the ability of Nagpra to protect Native American burials and remains, as intended by Congress.
"We are reviewing the court's opinion and will be considering all grounds for rehearing with the Ninth Circuit," said David J Cummings, attorney for the Nez Perce tribe.
Department of the Interior scientists say Kennewick Man is unlike any known modern Native Americans, although they do not rule out a distant biological connection.
Like other early Americans, Kennewick Man has a longer, narrower skull than is typical of present-day people.
Scientists want to know if this is because early settlers were replaced by ancestors of modern Native Americans, or if the differences are the result of evolutionary processes.
"It's the way forward," Dr Silvia Gonzalez, an expert in human origins at Liverpool John Moores University, UK, told BBC News Online.
"It's so rare, so unique to have [this specimen]. But unfortunately, we have already lost some very precious materials that are irreplaceable."
UK researchers fear they may soon face calls to relinquish human remains held by British universities and museums.
The Human Remains Working Group, commissioned by UK ministers, has recommended setting up a panel to investigate and adjudicate on ownership claims for material in British collections.
Dr Robert Foley, director of the Leverhulme Centre for Human Evolutionary Studies in Cambridge said: "I hope that when the [UK] government produces its consultation paper they'll look at the problems the American government ran into."