Kon Tiki, Aku Aku, Thor Heryrdahl, etc.
DNA studies have found no evidence South American Indians settled Polynesia thus proving Heyrdahl's theories of the settlement of Polynesia from South America incorrect.
Interesting lesson though - because of the spectacular nature of his voyage, his flamboyance, etc. people haven't really noticed the key fact he was wrong, and some nerds in labs with DNA who aren't interesting were right.