Kief just posted a kick ass review of a book called "The Power of Babel" which goes into depth explaining the origins of today's modern languages.
McWhorter backs up these concepts with many examples from languages and their evolution. He mentions a Roman scholar in the early centuries AD decrying the corruption of Latin in parts of the area, those corruptions later evolving directly into the French language. Lots of interesting tidbits come out, such as the fact that the rule against double-negatives, which is somewhat unusual to English (most languages, including Turkish, actually require the double-negative), was a peculiarity of an obscure dialect of English that got entombed into the language by an early grammar book.
Very cool. Probably not of much interest to anyone not struggling to learn a second language. But to those of us who've had to go back and relearn grammer later in life, you find yourself wondering how these wacky rules got started in the first place... this book seems to have a lot answers. Nice. Definitely going to be on the lookout for this one (or include it my next batch from Amazon.com).