I think they have been putting more scientists in space recently. For example Valeriy Polyakov (Russia) is a Medical Doctor, Michael Foale (England) studied astrophysics, James Voss (USA) who is from the U.S Army and was also an Aerospace Engineering, Ed Lu (USA) studied as an electrical engineering and physicist, Susan Still was a Test Pilot and also has a Master of Science degree, Sergei Krikalev (Russia) is a mechanical engineer.

I agree like Larry Jacks says that astronauts should be cross-trianed in the most important skills just in case the 'Mars-doctor' is likely to either get or die on the mission.