http://www.imdb.com/title/tt0411008/.../157473359?p=1
So this explains Jacob and Man in Black in a (pseudo)science context. If you go with this one could assume (thought it was there) that Jacob is positive and MIB is negative (or vice versa) in a magnetic field, balancing each other out, and why one can't directly kill the other. Was thinking perhaps one could from a distance but there's also that kid now who appears to be a referee so who knows. Nothing about all the Egyptian stuff either.
The polar bears make sense...as much sense as they could anyway.