The uniformitarian principle that knowledge of processes that operated in the past can be inferred by observing ongoing processes in the present is fundamental to historical linguistics. But there is an important respect in which the present is not like the past. For 97% of their history, human languages were spoken in neolithic and pre-neolithic societies which were societies of intimates, characterised by small size and dense social networks. A sociolinguistic-typological perspective suggests that the languages spoken in these communities may therefore have been typologically rather different from most modern languages, and that the methodology of ‘using the present to explain the past’ might therefore be less useful the further back in time we go.
http://www.csls.unibe.ch/studies/events/lectures_and_workshops/the_uniformitarian_hypothesis_and_prehistoric_sociolinguistics_what_were_stone_age_languages_like/index_eng.html
