The Inca never developed a system of writing, but they kept records and told stories through intricate knotwork. Learn what researchers know -- and what they're still looking to find out -- about Inca khipu in this episode of BrainStuff. Learn more about advertising on the HowStuffWorks podcasts at www.howstuffworks.com/advertisers.htmAnd to learn about your ad choices when listening to podcasts, visit https://www.howstuffworks.com/privacy.htm#ad-choices
