I am trying to remember the title/author of a book I read a few decades ago. It was I believe the following (kind of hazy). A group of aliens after completing college travel to earth to goof around. One of them gives apes/monkeys self awareness (which terrifies the ape/monkey). the other alien (brother ?) decides to not be as cruel and gives the ape/monkey a sense of humor so it can laugh at itself. They are punished by having to stay on earth and shepherd along the evolution of the species. The one with humor becomes a magnet for all the souls of the "party" people. and the other one (the studious one) becomes a magnet for all the serious people. This kind of forms a heaven and hell idea. That is about all I can remember. Any help would be appreciated.