Borders as a major theme in nation-state

When we think about nation-states today, we think about blocks, boxes, lines, and categories. As if they are one group.But is that really the case? Can or should nation-states really be defined by lines? Or I don’t maybe perhaps in my culture where the concept of “straight lines” don’t even exist? In Dinka, we have a word close to something like “round”, “oval” or other shapes that loop around, but not really linear in the way it is understood in English.How this idea came to be conceived and applied?In biology and taxonomy, scientists suffered and continue to suffer about deciding what a “species” really is. Is the Neanderthal indeed a different species from the sapiens, and the sapien sapiens? If yes, then how come some humans have traces of that species in some of us today? How do you categorize all those that fall into the cracks between the different species? A new species? Or belong to one of the others? Or to both or all of them?That is how I feel about the notion of states today. What about the differences inside them? As a Dinka living in Switzerland, I feel the cattle keepers in the Canton of Valais are culturally much closer to me as a Dinka man that many other tribes in South Sudan itself. Yet, they Valais cattle keepers feels fully Swiss, although when I see their practices of “inalpe” and “désalpe” – and the ringing bells along the necks of their cattle – I see exactly a Dinka man moving his cattle to highlands in Gogrial or Rumbek.What makes them Swiss and European and me South Sudanese and African? They are not Africans too? Even if all modern humans descended came from Africa? Is there a cut-off date when you lose touch with a place? Is it time? Color? Culture? And what is culture here? Because this culture looks closer to mine. Are borders just lines?