Laughter is man's response to being uncomfortable, discomfort causes us to bear our teeth and signal to the others that something is amiss.
We are chained to our sensations, as I think we are hard-wired to have a life filled with sensual experiences because it gives very pleasurable things to our brains.
Every time you hit the "post" button you get a tiny hit of dopamine. That's why this social media thing is so popular.