Final answer:
The infinite capacity to generate new messages in human language is called productivity or creativity. It is a unique biological feature that emerged through evolution, leading to significant cultural development and endless communication possibilities.
Step-by-step explanation:
Human language has an infinite capacity for generating new messages, which is a defining characteristic of our species. This feature is known as productivity or creativity. Central to the infinite possibilities of language are a set of rules governing how sounds, signs, words, and phrases can be combined to produce new meanings and convey a virtually endless variety of messages.
Through the processes of biological evolution, humans have developed the unique ability to invent, memorize, and communicate using a symbolic spoken language. This capability has been a major biological advantage and has led to the development of human culture. Unlike animal communication systems that are 'closed' and limited to context, human language is open-ended and allows for the continuous creation of new expressions and ideas.
Research into the emergence of language has been focused on human biological traits, such as our throats, brains, and genes, to understand what makes our flexible communication system possible. This evolutionary advantage is highlighted by the rapid development of language and culture in human history.