When Whales Walked: Journeys in Deep Time

Did you know that whales once walked the earth and crocodiles were once bipeds? Or that 95% of the bird population was wiped out in the last mass extinction? Or that elephants have grown shorter tusks to survive poachers? For generations, the histories of our planet's greatest creatures were a mystery, but thanks to new fossil finds and modern science, we're piecing it all together. Witness the surprising evolutionary stories of four remarkable creatures and the role humans may play in their next chapters.