It’s just that one can trace words back only so far. It is like the man who claimed to be selling Abraham Lincoln’s ax—he explained that over the years the head had to be replaced twice and the handle three times. Most linguists believe that after 10,000 years no traces of a language remain in its descendants. This makes it extremely doubtful that anyone will find extant traces of the most recent ancestor of all contemporary languages, or that that ancestor would in turn retain traces of the language of the first modern humans, who lived some 200,000 years ago.