Chrono, the comments on the video have lots of suggestions as to what the music might be, but I'd guess it was probably something custom written for the show. Discovery has poured more money into this than any other documentary ever. They spent 5 years and it was all filmed in HD.
That, and I saw the first 2 parts myself and it's the most amazing thing I've ever seen. I think you're alone here.
edit: I thought you were talking about Planet Earth, sorry. YOU GUYS SUCK