One of the major differences between man and his closest living relative is,of course,that the chimpanzee has not developed the power of speech. Even the most intensive efforts to teach young chimps to talk have met with 1 no success. Verbal language represents a truly gigantic stop forward in man's 2 . Chimpanzees do have a wide range of calls,and these certainly serve to convey some types of information. When a chimp finds good food he utters loud barks; other chimps 3 the vicinity instantly becomes aware of the food source and hurry to join in. In attacked chimpanzee screams and this may alert his mother or a friend,either of 4 may hurry to his aid. A chimpanzee confronted with an alarming and potentially dangerous situation utters his spine-chilling wraaaa-again,other chimps may hurry to the spot to see what is happening. A male chimpanzee,about to enter a valley or charge toward a food source,utters his pant-hoots and other individuals realize that another member of the group is arriving and can identify 5 one. To our human 6 each chimpanzee is characterized more toy his pant-hoots than by any other type of call. This is significant since the pant-hoot in particular is trie call that serves to maintain contact between the separated groups of the community. Yet the chimps 7 ' can certainly recognize individuals by other calls;for instance,a mother knows the scream of her offspring. Probably a chimpanzee can recognize the calls of most of his acquaintances. While chimpanzee calls 8 serve to convey basic information about some situations and individuals, they cannot for the most part be compared 9 a spoken language. Man by means of words can communicate abstract ideas,he can benefit from the experiences of others 10 having to be present at the time,he can make intelligent cooperative plans. (91)