Why is language unique to humans?

New research published today in Journal of the Royal Society Interface suggests that human language was made possible by the evolution of particular psychological abilities.

Researchers from Durham University explain that the uniquely expressive power of human language requires humans to create and use signals in a flexible way. They claim that his was only made possible by the evolution of particular psychological abilities, and thus explain why language is unique to humans.

Using a mathematical model, Dr Thomas Scott-Phillips and his colleagues, show that the evolution of combinatorial signals, in which two or more signals are combined together, and which is crucial to the expressive power of human language, is in general very unlikely to occur, unless a species has some particular psychological mechanisms. Humans, and probably no other species, have these, and this may explain why only humans have language.

In a combinatorial communication system, some signals consist of the combinations of other signals. Such systems are more efficient than equivalent, non-combinatorial systems, yet despite this they are rare in nature. Previous studies have not sufficiently explained why this is the case. The new model shows that the interdependence of signals and responses places significant constraints on the historical pathways by which combinatorial signals might emerge, to the extent that anything other than the most simple form of combinatorial communication is extremely unlikely.

The scientists argue that these constraints can only be bypassed if individuals have the sufficient socio-cognitive capacity to engage in ostensive communication. Humans, but probably no other species, have this ability. This may explain why language, which is massively combinatorial, is such an extreme exception to nature's general trend.