Sometimes you need to make sure you know what you're looking at before its scientific value is made clear – and that's the case with a 3,000-year-old piece of human bone initially thought to have come from a bear.

The remains were discovered in Lawyer's Cave in Southeast Alaska. The cave is on the mainland, east of Wrangell Island, and in the Alexander Archipelago, in an area inhabited by the Indigenous Tlingit people.

In cooperation with the Wrangell Tribe that now lives in the area, the ancient individual whose remains were found was named 'Tatóok yík yées sháawat' (TYYS for short). It translates as 'Young lady in cave'.

"We realized that modern Indigenous peoples in Alaska, should they have remained in the region since the earliest migrations, could be related to this prehistoric individual," says evolutionary biologist Alber Aqil from the University at Buffalo in New York.

After a detailed genetic analysis of the bone fragments, the researchers discovered that TYYS is closely related to the region's current inhabitants, in genetic terms – the modern coastal Pacific Northwest tribes Tlingit, Haida, Nisga'a, and Tsimshian.

This evidence of genetic continuity passed through the female line over the course of at least three millennia backs up the Tlingit declaration that they have been custodians of this part of Alaska since "time immemorial".

There aren't many other remains in this part of the world dating back thousands of years that have been discovered to date, but there are a few. Researchers compared them with TYYS to better understand how populations would have spread across this region.

Ancestry map
TYYS was compared to remains from other parts of Alaska. (University at Buffalo)

"Based on TYYS's nuclear genome, this individual is more closely related to Pacific Northwest coastal individuals than to inland peoples," write the researchers in their published paper.

"We find that the split between the coastal and inland peoples of the northern Pacific Northwest took place before ∼6,000 years ago."

That divergence between coastal and inland peoples is important for studying how North and South America were first inhabited. Travelers were thought to have crossed the Bering Land Bridge from Siberia some 17,000 years ago, though increasing alternate evidence exists.

As always, more research is needed to work out exactly what happened all those years ago, and discoveries are being made all the time; the genetic analysis carried out here wouldn't have been possible 20 years ago, the study authors say.

The only problem is the rarity of remains like these. That makes the discovery of TYYS an important new data point for researchers – at least once it had been established that it was a human rather than an animal.

"Many specifics of the population histories of the Indigenous peoples of North America remain contentious owing to a dearth of physical evidence," write the researchers.

"Only a few ancient human genomes have been recovered from the Pacific Northwest Coast, a region increasingly supported as a coastal migration route for the initial peopling of the Americas."

The research has been published in iScience.