In the decades after 1945, it became clear to the entire world that long range bombers and ICBM missiles could deliver near instant nuclear energy death (energy too cheap to meter) to anywhere in the world from anywhere in the world.
Even the wayward winds would help out, pushing the deadly radioactive fallout clouds hither and yon, willy nilly.
And that supposed boon to Progress , all those post-1945 ultra-fast civilian jets speeding business people and tourists from anywhere to everywhere in a few hours ?
All those jetliner routes also meant that thousands of very recently infected people could leave an area where a deadly infectious outbreak had not yet been medically detected, to make their way forth to innocently (and ultimately) infect the entire world --- all in the course of a day or two.
Gradually , our sense of the security we had always had that our own locality and our own nation-state could be a separate island of calm in a sea of global chaos has evaporated.
My claim that the post-1945 world is in an era of global commensality does not just mean the benign global re-cycling of oxygen, carbon, nitrogen, sulfur, phosphorus etc for the benefit of all life : it is not all cute lamb lying down with tame lion.
It also means the global re-cycling of radioactive clouds (and of Ebola viruses) to the detriment of all life.
It can mean that the baneful genetic effects of a nuclear explosion in this decade could still be harming our grandchildren in that decade --- for global commensality has a global time spectrum as well as global space spectrum.
It even means that one nation burning coal on this side of the world could raise the ocean waters enough to drown that island nation on the other side of the world.
Global commensality re-affirms that indeed no man, woman, child or beast is an island ....