Today, there are over 100 distinct beer varieties, from pilsners and bocks, to porters, stouts, and IPAs. The oldest evidence of beer brewing dates back 13,000 years, but experts believe the drink developed independently across the world. So, how did ancient civilizations brew beer, and how did their methods develop into the beverage we know today? Malcolm Purinton traces the evolution of beer. Lesson Malcolm Purinton, directed by Anton Bogaty.