Laughter

Laughter (Future)
Little is known about future laughter, since current time machines failed to mirror the rotation of the planet, and have sent time travellers hurtiling randomly through space. It is likely that they perished, unable to correctly recaliberate their time machine.

Laughter (Present Times)
Currently, it is fashinable to laugh at anything and everything. Many people that individuals would never have dared to laugh at historically, such the President of the U.S.A, the pope, and God, are often the centre of modern jokes. Also, famous figures are very popular individuals to laugh at. For example, it is currently fashinoable to imply that Justin Bieber is a girl, before laughing.

Laughter (Olden Days)
Back in olden Days, times were more conservative, meaning that people were very concerned with appearances. It often wasn't considered proper to smile, especially in pictures, so there's very little surprise that should be felt when it would be mentioned that old fashioned paintings do not depict smiling characters. In addition, a lot of jokes are centred in things that are slightly ridiculous (think of conversation topics of teens at lunch), and wouldn't have flown well in those times. It literally was a less funny time. Also, only men worked, and women were always at home stuck with 10+ kids. Imagine having 10 kids screaming at you. Would you have a smile? And the men weren't educated; they did hard labour jobs, nearly always. And they weren't allowed to show emotion. Ever. So they drank. And hit their wives and kids. And were very ashamed, but there were very few therapists in that time, since very few people were educated. Even in modern times, it is unfashionable for the older generations to seek theraputic assistance. However, they do laugh more now.