Back up to: Horizon
A controversial theory posits that for millions of years Earth was entirely ice covered.
A tiny, fossil jaw bone could solve the mystery of the 'missing link' in our evolution.
The extraordinary story of the twin boys who grew up as Brian and Brenda.
Packs of huge dinosaurs discovered in South America change our view of dinosaur life.
Horizon follows an expedition to the Andes in search of a missing plane. (2000)