Worth noting that India's oldest poetic/litergical traditions, the Vedas, were transmitted orally for at least 1500 years, and developed elaborate systems of memorization and pronounceation to ensure they passed down (almost) unmodified.
In Mauritania there is a village where most people who lived there are blind. This is how they learn to memorizw the Quran which is more than 600 pages, each have 15 lines.
