Gorillas are born with an international sign language of gestures that they use to communicate，says a new study from the University of St Andrews in Scotland.
From beating their chests to putting objects on their heads，shaking their arms，and even bouncing on all fours，the animals use more than 100 gestures to communicate with each other
Professor Richard Byrne，a psychiatrist involved in the research，says it was hard to figure out the meanings of the gestures.
“We don't really know what the animals are thinking. Often the gestures have more than one meaning，depending on the context，”says Byrne.
The study showed that the gorillas did not learn the gestures from each other，as had been expected，but performed them instinctively (本能地).
“Everyone had assumed different groups of gorillas would learn different gestures，”he says. “But that's not what we found. The more sites we went to ,the more we saw the same gestures being used. They seem to be naturally equipped with a pretty complex system of communication.”
The study also found that gestures were performed with close attention to the potential audience，so that silent signals，for example， were only given when other apes could see them. Other gestures，such as the "disco arm shake" were only ever seen directed towards humans.
Byrne believes that the findings may explain how the human language developed.
“There has always been speculation（猜测）that the origins of the human language might lie in gestures，”he says.
“Many researchers have therefore studied the gestural communication of the great apes for clues to the evolutionary origins of human gestures，”he adds.
Several studies have shown that great apes are capable of imitating gestures. However，the scientists found that what appeared to be copies of human actions were actually gestures the apes were already able to make themselves. They're “reusing” gestures from their own repertoire，not learning new ones.
64.According to the passage，Richard Byrne's research has found      .
A. different groups of gorillas would learn different gestures
B. gorillas know the sign language from birth
C. how gorillas learn from each other
D. gorillas develop a variety of languages when growing up
65.Why can't the researchers really know the meanings of gorilla gestures?
A. Because gorillas possess the ability of making many kinds of gestures.
B. Because they haven't made deep research into the animal.
C. Because a gorilla gesture may have different meanings.
D. Because gorillas can't exactly express their thoughts.
66.If a gorilla wants to make a silent gesture towards another gorilla，he      .
A. needs to know how many other gorillas are watching him
B. needs to make noise first in order to draw attention
C. will first make sure his gesture can be seen
D. will first consider whether he can carry out his gesture
67.According to the passage，many scientists study the sign language of great apes in order to      .
A. find the origins of the human language
B. find ways for people to communicate with apes
C. learn how animals communicate
D. discover the meanings of animal gestures