Sure, in their current boundaries. In fact, in 1939 Germany, it its current boundaries was just about the same age as Poland.
What we get into here is each “nation’s” belief that its own “historical boundaries” are sacred, while those of other “nations” are not.
And with all sides always forgetting that very often those they look backward to in justifying those historical boundaries had little if any conciousness of themselves at the time as being “a nation.”
For instance, a very popular ideology in Poland-Lithuania of the 17th century was “Sarmatianism,” under which the nobility considered themselves descendants of the Sarmatians of classical times. They had conquered and ruled over the local Slavs and eventually adopted their language. But the nobility were superior because of their ancestry. They didn’t consider most of the actual Poles, much less the Ukrainians and other “nations” they ruled to be deserving of any political rights.
http://en.wikipedia.org/wiki/Sarmatism
By this ideology there was no “Polish nation.” Only a group of peoples ruled over by the descendants of the Sarmatians, the Poles one of them.
True, that Nationalism as we know it today, is a fairly recent phenomenon. The founding of united Germany and united Italy in the 1800s probably served as the catalyst.