And what did they choose to lose? As another review made clear, the most interesting, the most novel and the most educational elements were discarded leaving a program that is still interesting if nothing else is available, but chopping out almost everything that made this program one of a kind.
The truth is, unlike many of the other fantastic 'life' installments, 'Life On Earth' is quite intellectual, and really oriented toward the college level viewer. That doesn't mean that younger people won't like it, but seeing it next to 'Life of Mammals' for instance, the difference in the target audience is abundantly clear. Unfortunately, almost all the college level material is dropped from the 4 hour version. Comparison to fossils, extensive discussions of evolution, co-evolution, speculations on the adaptive function of certain forms...almost all of this is gone!
I for one am a fan of all Attenborough's work, but 'Life on Earth' is by far one of the most amazing efforts in nature films and probably Attenborough's crowning achievement. It is (as tht title suggests) an overview of the world's natural history, crammed into thirteen fifty minute episodes with beautiful examples of every kind of life from all over the world. In the scope of science/nature documentaries, it is undoubtedly the finest of its kind.
For those who question where they might be able to purchase the entire series, I would suggest checking Amazon's UK branch as the BBC has issued the entire series there (though I don't imagine US machines will play it.)