Why the Paris sewers matter

The visit to the sewers, was, at least from my vantage point, fascinating.
To begin with, it seems important to remind ourselves that Paris is not just a state of mind, or a fantasy, but a real place with a beating heart. Nothing quite like seeing -- or smelling-- the wastes of Paris being carried off for treatment to make that point. Les egouts are real, in a way that the Rue de Rivoli can never be.
But beyond that, the sewers matter because they embody perhaps the single greatest innovation of the last 500 years. The realization that separating wastes from drinking water mattered has had a greater impact on human life than almost anything else you can come up with. A quick glance at what has happened to life expectancy, roughly (if a bit misleadingly) captured in this chart, makes this point. While it would be unnecessarily reductive to trace all increases in life expectancy to the invention of sewers, water wells and water treatment, there is a case to be made. In the developed world, the causes of death have shifted dramatically, from epidemics and infectious diseases to chronic systemic conditions (cardiovascular diseases, cancer, etc). The end of infectious diseases as a leading cause of death (and thus a limit on life expectancy) is a direct consequence of what we saw today.
There are subtle issues that the Egouts bring up, including the importance of material culture, and the role of everyday structures and objects in accounting for the rise and fall of nations and civilizations. French historians have pioneered this sort of analysis where the everyday lives of common people, and not the dramatic and elegant lives of the famous few, are the engine of social and historical change. We will be seeing plenty of Chateaux, of elaborate tapestries, of elegant paintings. They matter, but so do the egoutiers, their tools, and the life above the surface that they make possible. In short, I am suggesting that without the elaborate network of sewers that bring water in and wastewater out, Paris itself could not, and would not have existed.
And, of course, there is that famous scene in Les Miserables....