In one of his books (cannot recall title now) Konrad Lorentz (ethology study) describes the phenomenon of the appearance of a friendly smile as a spontaneous inversion of a warning grin. He does not make mention about laughter, though.
I am curious whether there is any work done on the evolution of laughter? Is there a connection with social organization? For example, crocodiles do not laugh.
Are there indicators on connections with a similar inversion mechanism as described above for the warning grin, e.g. a "warning roar" turning into laughter, for example?
