The world is full of communication. From sparrows chirping and talk radio in the morning to owls hooting and The Tonight Show at night, people and animals are constantly exchanging information through a wide variety of channels. However, there are some key differences between how humans and animals communicate. Specifically, human language is unique on the planet because it has the qualities of generativity, recursion, and displacement.

Generativity

Human language is generative, which means that it can communicate an infinite number of ideas. This is because it is combinatorial: words can be combined in different orders to create different larger meanings of a sentence. Animal communication does not have this freedom; animals communicate within closed systems, with limited possible ideas to communicate. Birds may have different chirps to signify danger or the location of food, but they cannot combine those chirps together to convey a novel meaning. 

Recursion

Human language is recursive. This means that we can put words, phrases, and sentences inside of themselves without limits. For example, we can say the sentence “Mark likes anchovies.” But we can also put that sentence inside of a sentence: “Carol thinks that Mark likes anchovies.” Then we can put that sentence inside of another sentence: “Greg said that Carol thinks that Mark likes anchovies,” and on and on forever. Obviously, the recursive abilities of language are constrained by the limits of time and memory. But in theory, because units of human language have the ability to be self-containing, we could have an infinite sentence. Animal communication does not have this same flexibility.

Displacement

Human language has displacement. This means that through the power of language, we can refer to things that aren’t present spatially or temporally. This is obviously a useful trait (it allows us to ask questions like “Where did I leave my wallet?”), and it is one that is largely missing from the animal kingdom. Bees actually do have limited displacement in their communication: They perform a waggle-dance to communicate to other bees the location of the most recent food source they have visited. However, there is no temporal nuance beyond this. Ants and ravens also have limited displacement systems.

Human language is also modality-independent—that is, it is possible to use the features of displacement, generativity, and recursion across multiple modes. Speaking is the auditory form of language, but writing and sign language are visual forms. There are also tactile forms, like Braille.

Origins of Human Language

The earliest origins of human language are hotly contested, as it is hard to find direct evidence for when people first began to speak. It is also likely that there was an intermediate period during which our communication systems were comparable to those of other primates, and even if we did have knowledge of what this was like, it would be hard to say exactly when we crossed over from animal communication to human language.

Proto-Indo-European

Proto-Indo-European (PIE) is the name for the common ancestor of the Indo-European language family. A language family is a group of languages descended from a common language. The Indo-European language family contains 445  current languages, and all of them are thought to have descended from PIE. 

Not all languages that have ever been spoken are still commonly used. For example, Latin, which was spoken in the Roman Empire, is now considered a dead language, or a language that has no native speakers.