A team of international scientists announced Wednesday that the remains of a six-week-old girl found in Alaska in 2010 yielded "the second-oldest human genome ever found in North America" — and one corresponding to a previously unknown lineage of humans, according to the New York Times.

Why it matters: The finding gives researchers some of the first archaeological evidence for how people came from Asia to the Western Hemisphere and supports the idea that Siberian migrants settled the Americas, per the Times.

• The girl, given the name Xach'itee'aanenh T'eede Gaay (which means "sunrise girl child" in the local dialect), was more closely related to Native Americans than other people living today, NYT reports, though she "belonged to neither the northern or southern branch of Native Americans."
• She is a descendent of the Ancient Beringians, named after the land bridge across the Bering Strait during the most recent ice age. The researchers suggest Ancient Beringians split from Native Americans' ancestors about 20,000 years ago.

But, but, but: There's debate among scientists on when Native Americans' ancestors split into different branches, per the Atlantic.

• One possibility is that they split into two lineages in Beringia, where the Ancient Beringians stayed, and the other side eventually "gave rise to the other Native Americans." This would mean there was only one migration.
• Others argue that the Ancient Beringians diverged from other Native Americans while still in Asia, and that both groups "independently traveled into Beringia and subsequently into the Americas," the Atlantic reports.