I've just been wondering? Is being ticklish one of the crucial elements that distinguishes humanity from the animal world?

Not at all!! Both my doggies are ticklish!

my cat is very ticklish on his paws!

I'm not sure about ticklishness, but laughter certainly seems to be one of the elements that distinguishes humanity from the rest of the animal world.

What about the laughing hyena, they cackle their heads off all day.

I'm sure lots of animals laugh but we wouldn't recognise the way they do it, they communicate (in a less sophisticated way than people) but I wouldn't understand what they where saying without a bit of observation and study. I find it hard sometimes to tell if people are laughing, crying or just acting and I've had to live with people all my life.

Ticklishness is responding to higher than usual pressure on a sensitive area and in humans this makes some of us laugh. But some people are boring and aren't ticklish at all.