A long-running debate over an ancient skeleton known as Kennewick Man has been reignited.
The 9,000-year-old was claimed as an ancestor by Native Americans, who called for his remains to be reburied.
However, a group of anthropologists said the specimen's features were not similar to people from local tribes and won a legal bid to study the bones.
Now a genetic analysis has revealed his DNA is more closely related to modern Native Americans than to anyone else.
The findings are published in the journal Nature.
The discovery of Kennewick Man along the shores of the Columbia River in Washington State in 1996 sparked a bitter legal battle.
For its age, the skeleton was one of the most complete ever found, and scientists said it could provide an unprecedented insight into America's early inhabitants.
However, local Native American tribes - who call the skeleton the Ancient One - said the remains should not be studied. And under the Native American Graves Protection and Repatriation Act (Nagpra), asked the US government to seize the bones and return them so they could be reburied.
This in turn prompted a lawsuit to block the move: scientists argued that the specimen had European features and could not be closely related.
In 2004, the scientists won - and began to study the remains.
Anatomical studies revealed that while Kennewick Man had similarities to Europeans, he also shared features with groups such as the Ainu in Japan and Polynesians.
However genetic advances have shed new light on the human's ancestry.
Scientists extracted DNA from a hand bone, and compared his genome with genetic data from around the world.
Study author Prof Eske Willerslev, from the Centre for GeoGenetics at the Natural History Museum of Denmark, University of Copenhagen, said: "The first important question we tried to address was to what contemporary population is Kennewick Man most closely related to. And it is very clear that the genome sequence shows he is most closely related to contemporary Native Americans.
"In fact we also got Ainu genome-wide data from a Japanese chief and we also had Polynesian (data) for comparison, as well as what is available across the world, and Kennewick Man did not show any significance in terms of having more Ainu or Polynesian DNA than other contemporary Native Americans.
"From that perspective, I think we can conclude very clearly he is most clearly related to contemporary Native Americans."
Further detail revealed that the genome was most closely related to DNA from the Confederated Tribes of the Colville Reservation, one of the five tribes who originally claimed Kennewick Man as an ancestor.
Although the four other tribes did not provide DNA, the researchers suggested that they would also be closely related.
Prof Willerslev said: "From my understanding of the history between these five tribes, there have been intermarriages between these tribes for many, many years, as far back as anyone can remember, so my expectation is that the other four tribes would also be closely related to Kennewick Man."
Jim Boyd, from the Colville tribe, told BBC News that he felt vindicated.
"We're very pleased with the finding... We've maintained the belief at the Colville community tribes that the Ancient One is a relative of ours," he said.
"This is proven now and we are very happy about this.
"We need the Ancient One to be respected and returned to the ground. That's what we believe and that is what many tribes around us believe."
It is not yet clear what will happen to the remains.
They are currently held by the Burke Museum at the University of Washington, which was designated as a neutral place to keep them. They are not on display and any access to Kennewick Man is regulated by the US Army Corps of Engineers.
Mr Boyd said his tribe and others were continuing their legal claim to reclaim the remains, and hoped that the latest genetic evidence would provide them with a stronger case.
The authors of the paper would not comment on whether they thought the bones should be returned to the ground or kept for scientific research.
However Prof Willerslev said: "I guess you can say there is some kind of irony.
"The reason why we can come to this conclusion scientifically speaking is because the remains were kept out for science.
"At the same time, you can say the conclusions show that Native Americans were right, and maybe it should have been a different decision in the first place."