[Sage]

They seemed to think it was just a genetic anomaly with no clear-cut benefits or disabilities. However, literally having no sense of humor might prove a problem in a social sense. If someone laughs at your jokes you tend to enjoy spending time with them, whereas someone who doesn't find you humorous at all will have to work extra hard to gain your friendship.
There's also a reproductive aspect: Poll after poll contends that people prefer a partner who can make them laugh, and having no sense of humor could be quite a stumbling block on the path to finding, and more importantly keeping, a mate.