If you’re in Siberia and end up in America, you must have lost your Bering.
And if it takes 12,000 years, the one thing you cannot be accused of is Russian.
Serious question: Since there was no writing, how can the linguists be sure that the language spoken 12,000 or 24,000 years ago bears any resemblance to today’s indigenous languages?
Exactly... They wrote nothing down and their languages were pretty much gibberish. So as far as linguistics go, modern generations are essentially making most of it up as they go along. They were stone age people when Europeans arrived with no horses, no metal work and they were essentially hunter gatherers... Without permanent residences and with no concept of ownership, wondering about the land and eating and existing on whatever they found. Writing wasn’t part of their existence until Europeans arrived.
Linguists can make “educated” guesses by comparing disparate languages about their origins and relationships. When the British colonized India, they began to study Sanskrit and noticed its affinity to ancient Latin, and to Proto-Germanic. Hundreds of years of scholarship has shown the affinities and history of Indo-European languages that goes back thousands of years. The same kind of scholarship can be applied to American languages.