translation.en: Other animals, like the social mammals -- the wolves, the elephants, the dolphins, the chimpanzees -- they can cooperate much more flexibly, but they do so only in small numbers, because cooperation among chimpanzees is based on intimate knowledge, one of the other.
translation.zh: 其它群居的哺乳类动物， 像是狼、大象、海豚、黑猩猩 － 它们的合作更灵活， 但规模有限， 因为黑猩猩合作的基础是 对彼此的亲密的认知。