This paper begins from the observation that human communication systems are unique in the animal world in varying on every level of form and meaning across social groups. There are some 7000 languages, each differing in sound systems, syntax, word formation and meaning distinctions. New information about the range of diversity and its historical origins has undercut the view that language diversity is tightly constrained by “universal grammar” or a language-specialized faculty or mental module. Instead languages seem rather to be historical accretions of finely honed practices, the product of cultural evolution and diversification over millennia.