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Laughter follows an evolutionary trail that could date back as far as 16 million years, said Marina Davila Ross, who led the study at the University of Portsmouth.

Laughter likely began as the "grunt-like" noises heard when gorillas, chimpanzees and orangutans are tickled and evolved into the higher-pitched laughter heard in humans, Ross' team reported in the journal of Current Biology.

"It is likely that great apes use laughter sounds to interact in similar ways to humans", Ross said. "This is important for emotional research in humans and animals as well as for the management of primates in captivity and in the wild."

Ross' team analyzed more than 800 sound tracks from "tickling sessions" involving 22 juvenile and infant apes and three human babies whose palms, feet, necks and armpits were tickled, The Daily Telegraph reported Friday.

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