Language is actually quite widespread in nature in its primitive form of communication (all animals communicate and even plants have some rudimentary form of interaction), although it is certainly unique to humans in its human form (but just like, say, chirping is unique to birds in its "birdy" form).
Language is very much a mirror image of the cognitive capabilities of the animal. Is human language really so much more sophisticated than other animals' languages?
Birds and monkeys employ a sophisticated system of sounds to alert themselves of intruders. The loudness and the frequency are proportional to the distance and probably to the size of the intruder. Human language doesn't have such a sophisticated way of describing an intruder. Is it possible that human language evolved in a different way simply because we became more interested in other things, than in describing the size and distance of an intruder?
There are three levels at which human language operate: the "what", the "where", the "why". What are you doing is about the present. Where are you going is about the future. Why are you going there is about the relationship between past and future.
These are three different steps of communication. Organisms could communicate simply in the present, by telling each other what they are doing. This is what most machines do all the time when they get connected. Living organisms also move. Bees dance to other bees in order to communicate the location of food ("where?"). Humans are also interested in motives ("why?") all the time. Without a motive a description often sounds incomplete. It is common in rural Southeast Asia to greet people by asking "what are you doing?" The other person will reply "I am rowing the boat". The next question will be "where are you going?" And the last question will be "why are you going there?" With these three simple questions the situation has been fully analyzed, as far as human cognition goes.
This does not mean that there could not be a fourth level of communication that we humans simply do not exhibit because it is beyond our cognitive capabilities.
There are other features that are truly unique to humans: clothes, artifacts, and, first and foremost, fire. Have you ever seen a lion wear the fur of another animal? light a fire to warm up? build a utensil to scratch its back? Why humans do all of these things? Are they a consequence of our cognitive life, or is our cognitive life a consequence of these skills?
Language Changes Minds
Language is a form of communication. The linguistic tradition focused on the mental processes of understanding language, thereby taking a "one-brain" view of communication. But communication, by definition, involves (at least) two participants, i.e. two brains. Communication -- and language in particular -- is a process between two brains. There is a neural process going on in one of the two brains and language is a means for that neural process to affect the neural process occurring in the other brain. Ultimately, "communication" is about one brain trying to replicate some kind of neural pattern into another brain. Language uses sounds/written symbols to induce such a mental replication. Those sounds/symbols are structured in such a way as to interact with the neural process of the other brain and cause it to create a specific neural pattern (that’s what we call "understanding"). This is an error-prone process that requires a lot of interaction, due to the fact that each brain is slightly different. But the goal is to eventually transmit a neural pattern from one brain to another. That pattern could be a scene or a story, if we are "narrating" something, or it could be a belief if we are trying to "convince" of something, or a concept if we are trying to explain something. It is a pattern that already exists in our brain and we want to recreate it in the brain of our interlocutor.
Needless to say, this implies that brains are capable of changing their neural patterns based on sounds/symbols. This is true of all species: bee brains must be capable of changing their neural patterns based on the dances of other bees. And must be willing to.
Naturally, once the pattern (a scene, a story, a concept) has been copied in the other brain, it takes on a life of its own because it interacts with the neural pattern that already inhabited that brain.
This complex interplay of brains must provide some significant evolutionary advantage if it appeared and became widespread among all species.
Species capable of learning are better at evolving. If language is such an efficient tool for learning that shapes an entire system of thought in a few years, then it is probably useful to survival and evolution.
Ultimately, language creates minds. We not only speak, but also listen. The listening is no less important than the speaking: the speaking expresses our mind, but the listening shapes our mind.
Communication and Ecology
Communication is two beings that engage in changing each other’s brain. That is actually the most natural phenomenon if one views life "top-down" and not "bottom-up". When we think bottom-up, we conceive life as many small beings making up societies and larger and larger entities (ecosystems) and eventually making up the Earth. It actually works the other way around: the Earth existed before life as we know it, and the Earth, at any point in time, is made of living components such as ecosystems, which are made of societies, which are made of individual beings. It is no surprise that all those ecosystems, societies and individuals are capable of communicating: they are merely "parts" of one giant organism, the Earth.
Communicating is their natural state. They are "parts" of the same organism.
Communication -- and therefore language -- is one of the most basic modes of living beings. When a bird sings in the woods, it is most likely telling other birds about the environment. The slightest disturbance will cause the tune to change. The bird singing in the woods is, therefore, reacting to sounds and smells and sights. The sounds the bird is making are "caused" by the environment and are in harmony with the environment. Those "sounds" communicate to other birds information about the environment. Indirectly it is the environment "talking" to the other birds, i.e. to itself.
Language is more than just sound. Language is sound (or vision, when you are reading) with a structure, and therefore packs more information than just sound.
Language carries meaning. This was a crucial invention: that you can use sound as a vehicle to carry more information than the sound itself. Again, the tip probably came from Nature itself: Nature speaks to us all the time. The noise of a river or the noise of an avalanche creates concepts in our minds, besides the representation of those sounds. Brain connections are modified at two levels: first to reflect the stimuli of the noise, and then to reflect what we can infer from the noise. Our brain can learn at two levels: there is a noise in that direction, and it is a river (meaning, for example, water to drink). Stimuli modify connections both at the level of perception and at the level of concepts. Language exploits this simple fact.
Sound is not the only way to communicate. Movement can also communicate. Sound is a particular case of movement.
The environment is a symphony of sounds, smells, sights and movement. Language is but one of the instruments in this symphony.
Anomalies of Language
The structure of any natural language is so complex that no machine has been able to fully master one yet. It is hard to believe that a child can learn a language at all. Its complexity should make it impossible at the outset.
If we analyze the way language works, we can draw two opposite conclusions: on one hand, the power of language looks overwhelming, on the other, its clumsiness is frustrating.
On one hand, we know that on average western languages are about 50% redundant: we would not lose any expressive power if we gave up 50% of our dictionary. We can guess the meaning of most sentences from a fragment of them. We also know that professional translators are able to translate a speech with minimal or no knowledge of the topic the speech is about.
On the other hand, we tend to believe that humans have developed amazing capabilities for communicating: language, writing, even television. However, in reality human communication is rather inefficient: two computers can simply exchange in a split second an image or a text, pixel by pixel or character by character, without any loss of information, whereas a human must describe to another human the image in a lengthy way and will certainly miss some details. Two computers could even exchange entire dictionaries, in the event they do not speak the same language. They could exchange in a few seconds their entire knowledge. Humans can only communicate part of the information they have, and even that takes a long time and is prone to misunderstandings.
Furthermore, why is it that we can accurately describe a situation, but not our inner life of emotions? Language is so rich when it comes to the external world, but so poor and inefficient when it comes to my inner life.
It has been noted that the ability to manufacture symbols gives humans a tremendous advantage (the ability to generalize experience and pass them on to other humans, so they do not need to repeat our mistakes or rediscover what we already discovered), but also a disadvantage, that accounts for many of our social and personal problems: there are fewer words (and concepts) than experiences. This means that we use the same word to describe different situations, objects, or feelings. No two apples are the same, but we use the word "apple" for all of them. Worse: we use the word "apple" even for the drawing of an apple, for the dream of an apple and for the string of characters "a-p-p-l-e", which are completely different objects. We tend to equate situations, objects and feelings that are actually different. We tend to define situations more often by "intension" (the "kind" they belong to) than by "extension" (the unique facts of a situation).
How can we then define our unique interiority? And talk about it?