As I write this I am on my way back from England to the Netherlands.
I will cross three borders.
I am allowed to do so because I carry a certain object, a hybrid of paper and plastic - that is, of tree and oil, of recent and ancient flora - that identifies me as a Dutch citizen, a member of a nation-state recognized by other nation-states.
The customs officers did not recognize me, of course (they don't know me), yet they recognized me, or rather the polity I belong to.
My passport doesn't mention this, but I am a Homo sapiens-Neanderthal hybrid. My hybrid ancestors have roamed the part of the earth we now call Europe for 40,000 years without encountering any borders. Read the full essay ...