Wells's biggest work is Outline of History, published in 1920, a picture of cultural evolution as the main theme of history since the emergence of our species.

Cultural evolution had its beginnings as soon as animals with brains evolved, using their brains to store information and using patterns of behavior to share information with their offspring. Social species of insects and mammals were molded by cultural as well as biological evolution. But cultural evolution only became dominant when a single species invented spoken language. Spoken language is incomparably nimbler than the language of the genes.