Borders
Humans are so frightful that they have to build borders all the time. This is mine and that is yours, or better: this is mine and I will not share it. Every century there seems to be a period where people overcome these primitive sentiments for a while but then follows a time where power-hungry sociopaths exploit these inherent fears and start to build borders again.
Today elected representatives in the Untidy Kingkong shouted 'get Brexit done', but what they really meant is: 'we will build a wall, and we will not share our riches'. Shame on them.