The big problem with theories of humour is not that they are sombre; it is that they are often implausible or myopic.
All of the usual suspects have their shortcomings. Surveys typically list three broad varieties of humour theory: superiority theories, release theories and incongruity-resolution theories. Superiority theories say that humour illustrates the inferiority in some respect of the joke’s butt, provoking laughter as a sort of small triumph in the superior witness. This works well in some cases, but struggles to account for “butt-less” humour such as puns, or the kinder forms of imitation. Release theories have a Freudian pedigree: humour provides a sort of relief from a build-up of nervous tension. Again, it is not clear that one can plausibly think of simple puns as having such therapeutic functions, and many of today’s cognitive scientists are sceptical of the more general hydraulic metaphors used to depict build-up of energy, overflow, release and so forth. Incongruity-resolution theories are more popular: they assert that humorous situations involve the presentation of an incongruity that is subsequently resolved. Here we might be concerned about whether “incongruity” and “resolution” are understood in suitably precise ways: without such tightening, the theory seems vulnerable to counter-example. In The Emotions and the Will (1875), Alexander Bain complained that “There are many incongruities that produce anything but a laugh”, and went on to list many examples that are not funny, and that would remain unfunny even if they were, in some sense, resolved: “snow in May, Archimedes studying geometry in a siege; . . . a wolf in sheep’s clothing; . . . a corpse at a feast, parental cruelty”.
Perhaps the more that something seems comic rather than tragic is a sign of economic progress?