The 20th century was one where mankind decided, with all its great knowledge of the natural world, to neatly organize life into boxes.
Remove food from where we live, separate work and life, family and vocation. Not just actively — physically the farm, home, and work were scattered across the map and assigned specific districts, now that a we had fancy automobile to zoom around in (also separate, alone).
The result was catastrophically global ruin.
The critical goal of the 21st century will be to learn to fully appreciate the interconnectedness of life, and put the pieces back together.