Language is a uniquely human faculty. It is true that all animals communicate with each other through sounds, smell and body language. But by definition this sort of communication is not language. Simply put, language is defined as words linked to objects and concepts. The words in turn can be chained into sentences that follow grammatical rules. Some species like parrots and chimpanzees can be trained to understand sentences used by humans. However, this is a one way communication they could not reciprocally ‘speak’ or express themselves in a broad range. What gave rise to language in humans is the need to represent human ‘action’. Beyond this utilitarian purpose, through evolutionary mechanisms language has now developed into a tool for imagination and abstract thought.
Several species of whales, monkeys, birds and lizards have been shown to communicate using their language of signals. Yet, this sensory based communication cannot be considered language. A language system is identified through the components of words, logical phrases, complete sentences and a set of grammar rules. While surely parrots can memorize hundreds of words and phrases, they are incapable of making sentences on their own. Likewise the intellectual capacities of higher apes are not sufficient for them to imagine through the use of language. To this extent, language is a uniquely human feature. Our language allows us to write sublime poetry, just as it allows us to write nonsensical (yet grammatically correct) sentences.
Goldman, Jason G. (7th October 2012) Is Language Unique to Humans? taken from: http://www.bbc.com/future/story/20121016-is-language-unique-to-humans/all on 10th March 2013.