[KS] Languages in Korea

[rupert]

Has there gernerally been one language spoken on the Korean peninsular or were there in previous times more than one? I ask this because someone (more related to Japan) is trying to persuade me that Korean had as many as six languages and that one of them went over to Japan, and supposably died out in Korea. This does not seem right to me. And while on this track, how about China? Today we have Mandarin and Cantonese. How many languages were there in the past? Do others still exist today? 

Is he right? If not, I would welcome some ammunition for my next conversation.

Rupert Atkinson