According to a recent article in The New Scientist, the ground-breaking physicist Murray Gell-Mann* has been spending his twilight years (he's now 80) trying to "trace the majority of human languages back to a common root." This tower of babel quest is roughly the Grand Unified Theory of linguistics. And just like the GUT of physics, it is about as fruitless. Many have tried, all have failed. Where Einstein failed with GUT (as well as many others), Murray Gell-Mann is likely to fail in linguistics. It may be the case that all human languages are descendant from a single progenitor (doubt it), but I see no reason to believe there exists evidence to prove it one way or the other. Language has simply not been preserved the way fossils have and language doesn't have the sort of physical reality that elementary particles have. So chasing that tail is is going to end up exactly the way all tail-chasing adventures end.
*fyi, his ground-breaking work involved categorizing elementary particles.