What can we learn from a theory of Japano-Koreanic common origin?

Where do Japanese and Korean come from? This lecture explores the strengths of the "Proto-Japano-Koreanic" theory, which proposes that Japanese and Korean descend from a common ancestral language spoken about 5,000 years ago. It presents an overview of their linguistic similarities and differences, key evidence for common ancestry that cannot be explained as later borrowings, and a broad picture of how Japanese came to be spoken where it is today. Special attention will be given to how this theory helps explain phenomena in both languages that would otherwise remain mysterious.