WASHINGTON, D.C.—Linguists Mark A. Sicoli of Georgetown University and Gary Holton of the University of Alaska have examined the shared grammatical features of Yeniseian and Na-Dene, thought to have descended from a common language some 12,000 years ago. Yeniseian is a group of mostly extinct languages spoken along the Yenisei River in central Siberia, and Na-Dene, which is spoken in Alaska, western Canada, and is also related to Navajo and Apache. Sicoli and Holton think that this lost mother tongue was spoken in Beringia before the speakers split up: one group would have moved east into North America to become the Na-Dene speakers, while the other group would have migrated back into central Asia and became Yeniseian speakers. “There may have been multiple streams of people moving out of that single source at different times,” Dennis H. O’Rourke of the University of Utah commented to The New York Times.