The evolutionary origin of laughter

In his book Sweet Anticipation: Music and the Psychology of Expectation, David Huron does some fascinating speculation about the evolutionary origin of laughter.

1. Unvocalized panting occurs in response to surprise. This panting is part of a generalized increase in physiological arousal. Like the gaping mouth of the “surprised” face, panting prepares the animal for action.
2. For highly social animals (like humans and great apes) the biggest dangers come from other members of our species (conspecifics).
3. Threats from other conspecifics also evoke unvocalized panting. The threatening animal recognizes the panting as a successful provoking of a momentary state of fear in the threatened animal. The evoked fear means that the threatened animal has been successfully cowed. Panting becomes a signal of social deference. As an aside here, we might note that dogs exhibit “social panting” where submissive animals begin panting when a dominant animal (sometimes a human owner) appears.
4. Being able to evoke panting in another animal reassures the dominant animal of its dominant status. Similarly, panting in the presence of another animal serves to communicate one’s submissiveness. For the submissive animal, this communication is valuable because it establishes the animal’s submissive status without having to engage in fighting.
5. In order to enhance the communication of deference, panting becomes vocalized — that is, the vocal cords are activated. Vocalized panting becomes a specific signal of deference or submissiveness.
6. Vocalized panting generalizes to most surprising circumstances.
7. In some primates, “panting-laughter” is reserved specifically for surprise linked to nondangerous outcomes. In highly socialized animals, most dangers are social in origin, so panting-laughter is commonly associated with social interaction.
8. In hominids, panting-laughter becomes explicitly social. Mutual panting-laughter within a group becomes an important signal of reciprocal alliance, social cohesion, and peaceful social relations.
9. The contrast between negative reaction feelings and neutral/positive appraisal feelings evokes an especially pleasant state. Human culture expands on these agreeable feelings through the advent of “humor” as an intentional activity meant simply to evoke laughter.
10. Laughter becomes commonplace in hominid social interaction. In order to reduce the energy cost of laughter, the inhaling-exhaling form is replaced by the more efficient vocalized exhaling (i.e., modern human laughter).

What do we think? I find this to be a convincing theory.