People have talked about for centuries if we can establish a "Proto-World" language from which all human languages descend. A famous example stating this has been the story about the tower of Babel. Traditional historical linguistics state that so far it has been impossible to show that all the world's languages are genetically related.
The American linguist Joseph H. Greenberg claimed that long-distance relationships can be shown by applying an approach he called mass comparison. The languages are compared by using a limited set of words (including function words and affixes) simply by means of counting cognates. He used this method to establish a classification of African Languages.
His work has generated considerable interest outside the linguistic community. It is still much debated.
see also: Nostratic language
Hans Henrich Hock and Brian D. Joseph - Language History, Language Change, and Language Relationship An Introduction to Historical and Comparative Linguistics Mouton de Gruyter, Berlin 1996; chapter 17