clipped from: wtopnews.com 
That's how researchers made a variety of apes and some human babies laugh. After analyzing the sounds, they concluded that people and great apes inherited laughter from a shared ancestor that lived more than 10 million years ago.
As far back as Charles Darwin, scientists have noted that apes make characteristic sounds during play or while being tickled, apparently to signal that they're interested in playing.
It's been suggested before that human laughter grew out of primate roots. But ape laughter doesn't sound like the human version. It may be rapid panting, or slower noisy breathing or a short series of grunts.
So what does that have to do with the human ha-ha?