What education or training is required to become a cartoonist?

It depends on what you mean by Cartoons. Do you mean the ones in the local Sunday paper, comic books, basic old school animation or contemporary animation like Pixar produces. I don't think an education level is necessarily required for the 1st example and perhaps not for the 2nd. I believe it is probably based on talent and experience. However, an art degree with an animation focus probably would be very beneficial for these avenues and it would probably be required for the last two examples. Computer programming knowledge would also be important. My suggestion is go straight to the source. See if Pixar or similar production companies have websites. They may have biOS on their creative teams that could list credentials.