Why? Well, Joe's super-science web series, 'It's Okay to be Smart' is ready to help with the answer to that - with plenty of science puns along the way.
Hanson's webseries focuses on a different question every week, from the science of running a marathon to the question of whether Santa is real.
In this video he explains that laughter isn't like speech - it's a much more basic vocalisation. Hell, even rats do it (in a super high-pitched way) and apes, too.
It's a funny old world.