Charles Darwin dropped out of medical school because the sight of blood made him faint, nearly became a country parson, and spent five years on HMS Beagle vomiting over the rail from chronic seasickness. Nothing about this anxious, sickly young man suggested he would produce the most revolutionary idea in the history of biology — the theory of evolution by natural selection.

This episode traces Darwin from his failed medical studies through the Beagle voyage that opened his eyes, the twenty years he spent sitting on his theory in terror of the backlash, and the publication of On the Origin of Species that changed humanity's understanding of life itself.

• Darwin's failed medical career and his unlikely path aboard HMS Beagle
• The Galapagos finches, coral reefs, and observations that sparked the theory of evolution
• Tw ...