They are very much alike, yet different : the East-Slavic languages. Russian, Ukrainian and Belarusian have a lot in common. All three of them have, for example, six cases, two verbal aspects and no articles, which places them apart from other Slavic languages such as Bulgarian and Polish. Yet, even among the closely related and strikingly similar East-Slavic languages, one can observe linguistic differences that are too great to neglect.
Over the years, many linguists have attempted to explain how the three East-Slavic languages came to be and in doing so, tried to find an explanation for the differences between the languages. Interesting to note is that for a long time, in both czarist and Soviet times, a common held belief was that Belarusian and Ukrainian were basically nothing more than Russian dialects that were ‘tainted’ by influences from Polish. Linguists like Aleksej Šaxmatov (1894) and Fedot Filin (1972) came up with theories that more or less supported this claim. Šaxmatov blamed the Tater invasions for causing a large displacement of Russian tribes (which, for example, enabled the future Ukrainians to leave the Carpathian mountains and settle in the plains and occupy Kiev). As a result of this displacement new contact between the various displaced tribes lead to the formation of the contemporary East-Slavic languages. Soviet linguist Filin explained the existence of the three East-Slavic languages by proposing the existence of ancient isoglosses – i.e. ‘boundaries’ that limit the geographic area in which certain sound laws are in place – that existed even before the emergence of East-Slavic as a separate branch in the family tree of the Slavic languages. When the Russian settled in the Russian plains and started expanding their territories, they moved across such isoglosses, which then lead to the emergence of Belarusian and Ukrainian.
However, other linguists, such as Stefan Pugh (2007) take on a less Russian-centred approach to explaining the origins of the three East-Slavic languages. Pugh explains the differences between Russian, Ukrainian and Belarusian by pointing out the fact that over the course of time, large parts of the East-Slavic lands were gradually brought under control of at first the Grand Duchy of Lithuania and later on the Polish-Lithuanian Commonwealth. By annexing the territories of modern-day Belarus and most of central and western Ukraine, Pugh states, the Commonwealth divided the East-Slavic languages. The East-Slavic spoken in the annexed lands became heavily influenced by Polish, which was more or less the official language of the Commonwealth.
To test the plausibility of thesee theories I undertook a study of East-Slavic morphology (i.e. the way in which word forms change as their meanings are changed). I decided to focus on a selection of morphological samples topics in which one could fairly easily distinguish between a Polish and Russian form. Based on these topics, I made a selection of non-religious texts originating from the Belarusian, Ukrainian and Russian language areas. The analyses involved one text from every language area from every other century (i.e. 14th, 16th and 18th century) , as well as an additional text from the 13th century when, – according to various sources,Common East Slavic started falling apart.
During the investigation it became clear that in Belarusian and Ukrainian various morphological features changed and became more similar to corresponding Polish forms. This change took place somewhere during the 16th-17th centuries, when, following the Treaty of Lublin (1569) the Polish-Lithuanian Commonwealth was created and the contacts between the Kingdom of Poland and the Grand Duchy of Lithuania further intensified. After the treaty, Polish quickly became the official language of the Commonwealth, gaining a dominant position over Belarusian and Ukrainian.
As a result of this sudden switch from Russian to Polish forms and the Treaty of Lublin, Polish became a dominant language over Belarusian and Ukrainian. This makes Pugh’s assumption that major linguistics differences between Belarusian, Ukrainian and Russian were caused by heavy influence from Polish, fairly plausible. One can therefore safely say that Polish contributed to the richness and variety in the East-Slavic languages and helped them become what they are today.