how to explain the “but” in this sentence？but在这里什么意思，貌似并不是表对比 The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, but this is largely because, animals, we stand upright. i don't this “ but ” in this sentence is used to introduce a statement that adds something to a previous statement and usually contrasts with it in some way. how to explain it？