A new study suggests humans and great apes have been giggling in similar ways dating back 15 million years. Many other animals also laugh, but the giggles don’t match human patterns as closely. Scientists trying to uncover how laughter evolved recorded apes and children being tickled. Primatologist Chiara De Gregorio at the University of Warwick concluded that gorillas, orangutans and humans laugh in similar rhythms. But human laughter has become faster and more complex, sounding different based on context, from a polite chuckle to a full-bodied guffaw. Her research was published Thursday in the journal Communications Biology.