Did Laughter Make The Mind?
The objection to this theory is that ape tickle-play vocalisations don’t sound like human laughter at all – they are more like heavy breathing, with inhalations and exhalations equally audible. By contrast, when humans meet up on social occasions, the most frequent sounds you’re likely to hear are not grunts and screams but ripples of laughter. This has become so habitual that our instinctive social signals, inherited from our primate ancestors, have been largely repurposed: the tense primate fear-grin has given way to the relaxed human smile, while the angry mobbing cry has transformed into uproarious laughter.
Source: aeon.co