I was talking to a friend and he mentioned that some mummies were found that had traces of tabacco in their bodies. That would mean that long distance trade occurred long before the 15th century.

The claim that cocaine and tobacco has been found on ancient Egyptian mummies is highly dubious. About a month ago, I made a post over at /r/badhistory, where I hit some of the primary issues with this idea:

[T]his all goes back to a pair of German studies in the 1990s. Here's a response made to the original study. It's important to remember that the original studies didn't find tobacco or coca leaves on the mummies, just chemical signatures that were suggestive of those plants. In addition to the suggested contamination routes mentioned already [people smoking around the mummies post-1500] , the mummies might have been contaminated with those chemicals by older insecticides that contained them or chemicals that could decay into them. Alternatively, it might have been plants used in the mummification process (the exact process and its variants being unknown, but suitable plants bearing low concentrations of cocaine-like chemicals being known from Africa).

A final, but significant criticism of the original study, is that the mummies are of uncertain provenance. No one is sure where they came from or what treatment they might have receive before reaching the researchers.