A — 5: to trace the origin of laughter back
B — 1: that laughter is a uniquely human trait
C — 6: whether laughing emerged earlier on than humans did
D — 3: while their caretakers tickled them
E — 7: that humans were closest to chimps and bonobos
F — 4: that laughing comes from a common primate ancestor
Laughing and evolution
The first hoots of laughter from an ancient ancestor of humans could be heard at least 10 million years ago, according to the results of a new study. Researchers used recordings of apes and babies being tickled __to trace the origin of laughter back__ to the last common ancestor that humans shared with the modern great apes, which include chimpanzees, gorillas and orangutans.
The finding challenges the opinion __that laughter is a uniquely human trait__, suggesting instead that it emerged long before humans split from the evolutionary path that led to our primate cousins, between 10m and 16m years ago.
“In humans, laughing can be the strongest way of expressing how much we are enjoying ourselves, but it can also be used in other contexts, like making fun of someone,” said Marina Davila Ross, a psychologist at Portsmouth University. “I was interested in __whether laughing emerged earlier on than humans did__.”
Davila Ross travelled to seven zoos around Europe and visited a wildlife reserve in Sabah, Borneo, to record baby and juvenile apes __while their caretakers tickled them__. Great apes are known to make noises that are similar to laughter when they are excited and while they are playing with each other.
Davila Ross collected recordings of laughter from 21 chimps, gorillas, orangutans and bonobos and added recordings of three babies that were tickled to make them laugh.
To analyze the recordings, the team put them into a computer program. “Our evolutionary tree based on these acoustic recordings alone showed __that humans were closest to chimps and bonobos__, but furthest from orangutans, with gorillas somewhere in the middle.” said Davila Ross. “What this shows is strong evidence to suggest __that laughing comes from a common primate ancestor__.”