I may be wrong but I think I've discovered the root of all mashup/remix culture. Dutchman Jaap Eggermont may have started the entire scene back in 1981. Using a fixed tempo and studio reproduced recordings of famous 60's hits he produced a single called stars on 45 medley. The idea behind is was to get a more disco friendly version of classic well known hits. Which pretty much sums up about 80% of todays remixes (smells like teen spirit?). The medley samples mostly Beetles songs but has a few other gems in there.
Stars On 45 - Medley
This is a much more recent track released in 97. It features a bunch of 80/90s housey/trancey/black female vocally stuff which you will recognize.
Stars On 45 - Club Hits