Misinformation about this subject is commonplace - a good source of open info can be found at
http://spaceflight.nasa.gov/shuttle/.../asseltrn.html
But some relevant bits:
"For mission specialists and pilot astronaut candidates, the education and experience requirements are at least a bachelor's degree from an accredited institution in engineering, biological science, physical science, or mathematics"
The medical is thorough, but you do not need to be superhuman.
MT
tater - PM for you.