The source of the earth's great variety of animals was a scientific mystery until Charles Darwin proposed the idea of natural selection. Nova presents breakthroughs in a new science nicknamed "evo devo" that are linking the enigma of origins to another of nature's mysteries, the development of embryos.

Documentary. Based on the books: Endless forms most beautiful ; and, The making of the fittest / by Sean B. Carroll. Originally produced for the television program on Nova in 2009.

Unanswered questions -- The Galapagos -- Descent with modification -- Natural selection -- The magic of DNA -- 23,000 genes -- Fruit flies -- Gene switches -- A transitional form -- From fins to limbs -- The hand -- Our brains -- What makes us human?