Language mainly a cultural phenomenon
A report I found the other day suggests that language is most likely to be mainly a cultural phenomenon and that any genetic underpinnings for language probably pre-date the emergence of human language.
Researchers in the UK and USA modelled how aspects of language might have been encoded genetically and concluded that this was very unlikely to have occured given the way human culture changes. For linguistic traits to become encoded in the genes they have to provide a selective advantage and there has to be a stable language envirnoment. Human languages change too quickly for this to happen, and modern humans haven’t existed for long enough either. Therefore they believe that language evolved culturally and that the existence of a genetic language module is unlikely.
They also argue that if human populations in different parts of the world had evolved separate, incompatible language modules, they wouldn’t be able to learn one another’s languages. This is obviously not the case.