Question: why do we laugh?

Ian van der Linde answered on 11 Jun 2011:

Good question! Monkeys and other animals make laughter-like sounds too (rather like heavy panting) when they’re doing something enjoyable like being chased or tickled, so laughter isn’t just human. A theory is that laughter is a way of communicating with our peers during “play” – to let them know that we’re willingly participating or paying attention to them.

Researchers have found that people very rarely laugh on their own, so it’s all about communication with others – however, given that we know that animals do it too, its likely that laughing is a very old and primitive form of communication that evolved much earlier that speech!