The article says that words like "fire", "ashes", "bark", and "worm" could be 15K years old, but doesn't provide any idea of how they might have sounded back then. The original paper linked at the bottom doesn't seem to help in that regard, either.
Is this something that we simply cannot know with current methods? Ice Age people obviously didn't leave any sound recordings, but surely some of the sounds would have to be present in a similar form in order for us to say with confidence that a it's the same word?
Searching for "fire" gives a bunch of different results; I have no idea which one they used. The one closest to English is probably "*ṗVxwV" (where V stands for any vowel, I believe).
Is this something that we simply cannot know with current methods? Ice Age people obviously didn't leave any sound recordings, but surely some of the sounds would have to be present in a similar form in order for us to say with confidence that a it's the same word?