Earth teems with a staggering variety of animals, including 9,000 kinds of birds, 28,000 types of fish, and more than 350,000 species of beetles alone. What explains this explosion of living creatures? The source of life's endless forms was a profound mystery until Charles Darwin's revolutionary idea of natural selection, which he showed could help explain the gradual development of life on earth. But Darwin's radical insights raised as many questions as they answered. What actually drives evolution and turns one species into another? And how did we evolve? NOVA reveals answers to the riddles that Darwin couldn't explain. 120 min.  Movie starts at 3pm!