The transcript of the Nova program “In Search of the First Language” is well worth reading; the discussants are real linguists, unlike so many of the talking heads that wind up on TV (I went to grad school with one of them), and you can learn a lot from what they say. But as I wrote on the Wordorigins thread where this was posted, you should take this caveat very seriously:
This picture that Dolgopolsky paints of the Proto-Nostratic world is controversial and not widely accepted. In fact, most linguists argue that any attempt to come up with a language spoken fifteen thousand years ago is pure speculation.
Nostratic is wishful thinking. The rest is real linguistics.