Going down into these narrow flooded passageways is not for the faint-hearted but, with only an estimated one percent of the caves explored, it is an opportunity for the team to write themselves into cave diving history, by pushing further in than anyone has before. This is a challenge that tests even the most accomplished cave divers. Steve must face the terrors of being lost in an underwater silt cloud in a cave. But there is a bigger issue at stake. All life in the Yucatan depends on the fresh water in this network of caves, but it's being contaminated by human development. With every metre the team maps, it adds to the knowledge of the system, which, in turns, helps protect it for future generations.
Reconstructing a dinosaur skeleton for a museum is a balance between art and science - but getting that balance right is a tricky diplomatic, as well as scientific, process. Presenter and anatomist Dr. Alice Roberts follows the reconstruction of L.A.'s Natural History Museum's 2011 dinosaur exhibit.
2011 • Nature
David Attenborough visits archaeological sites where fossils were found illustrating the origins of life on earth, in the ocean. For long, evolution worked very slow and species remained primitive, mostly single-cell, alter fractal. Only the invention of sexual reproduction kick-started genetic diversification.