A baby girl who died in Alaska some 11,500 years ago belonged to a formerly-unknown population group whose discovery has shed light on the peopling of the Americas, a study of her genome revealed Wednesday.

By decoding the child's genetic fingerprint, scientists could look back on the history of the first people to conquer the New World, and conclude they likely arrived from Siberia some 20,000 years ago.

"The study provides the first direct genomic evidence that all Native American ancestry can be traced back to the same source population during the last Ice Age," researcher Ben Potter of the University of Alaska told AFP.

Potter and a team analysed the DNA of an infant whose remains were unearthed at the Upward Sun River archaeological site in Alaska in 2013. She was named Xach'itee'aanenh T'eede Gaay (Sunrise Girlchild) by the indigenous community, and her genome "provided an unprecedented window into the history of her people", said Potter.

The team had expected the girl's genetic profile to match that of known Native American groups.

Instead, it showed she belonged to a completely new group, which they named Ancient Beringians.

"Prior to this study, we did not know that this Ancient Beringian population existed," said Potter.

Critically, the girl's genome also revealed the identity of a common ancestor her people shared with Native Americans.

This common forebear or "source population", which the team dubbed Ancestral Native Americans, emerged some 36,000 years ago in what is Russia today, splitting from East Asians, whose progeny include the Han Chinese.