What is dene-yeniseian?

Dene-Yeniseian is a proposed language family linking the Na-Dene languages of North America and the Yeniseian languages of Siberia. This proposed language family is based on similarities in grammar, pronunciation, and vocabulary. Linguists propose that the ancestors of the Na-Dene-speaking peoples migrated from Asia to North America around 20,000 years ago and that their language evolved separately from the Yeniseian languages that remained in Siberia. Some linguists have proposed that the Dene-Yeniseian family is related to a broader hypothetical language family called Dené–Caucasian, which includes languages spoken in the Caucasus Mountains, North Africa, and western Asia. However, this proposal remains controversial and has not been widely accepted.