BOISE - The U.S. government is negotiating with three Native American tribes to return the 500-year-old skeletons of a young adult and child found at a southwestern Idaho site that authorities first thought was a more recent crime scene.

The U.S. Bureau of Land Management says the Shoshone-Bannock Tribes, Shoshone-Paiute Tribes and the Nez Perce Tribe have each made formal claims for the bones.

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The federal agency is using a process spelled out in the Native American Graves Protection and Repatriation Act and expects a decision this spring.

Carbon dating found the young adult and child or teen lived sometime during the 1400s to 1600s.

Anthropologists say they'll lose a unique research opportunity to learn about how the two lived and died so long ago.