Interesting article by Steven Johnson in the New York Times about human life expectancy. Up until around 1750, average human life expectancy seems never to have cracked about 35 years. It often fell below that figure, due to disease or famine, but never rose above it. This was true for all classes of society; so far as we can tell (obviously the data sets are small) aristocrats had about the same life expectancy as peasants or slaves. That's because disease did not care about your status:
During the outbreak of 1711 alone, smallpox killed the Holy Roman emperor Joseph I; three siblings of the future Holy Roman emperor Francis I; and the heir to the French throne, the grand dauphin Louis.
Modern statisticians have noticed that this began to change in the 1700s. It changed first with aristocrats; historian T.H. Hollingsworth showed that by 1770 the life expectancy of British aristocrats had risen to 45 years. This change pointed the way to the modern demographic regime, in which everyone lives much longer but the rich live significantly longer than the poor. One factor singled out by Johnson is variolation, a sort of primitive inoculation that was used in many parts of Asia and brought to Britain from the Ottoman Empire in the 1720s. But since life expectancies in the Ottoman Empire and India were not above 35 and probably much less I'm not convinced; maybe variolation worked much better when administered by skilled and therefore expensive physicians. Jenner's vaccination technique, introduced in the 1790s, worked much better.
Anyway life expectancies in rural Europe continued to rise through the nineteenth century; one British statistician found that by 1843 it had reached 50 in mostly rural Surrey. But the overall life expectancy of Europeans rose more slowly, because of the dire situation in industrial cities. In 1843, again, life expectancy in Liverpool had fallen to 25. This had many causes, including pollution, cholera, and gin, but one singled out by contemporaries was bad food. Before refrigeration it was just very hard to get massive quantities of fresh food into dense urban neighborhoods without spoilage, so poor urban people were regularly eating dubious meat, cheese, fish, and especially milk. That's why Louis Pasteur got so famous; not for disproving the spontaneous generation of microbes but for making milk safer at a time when spoiled milk was sickening millions. If the poor tried to avoid such dangerous foods they ended up living on fried potatoes and beer, which is unhealthy in other ways.
And here we get to the part of the story that really interests Johnson. What reversed this trend and got urban life expectancies rising was not so much scientific advances, although those were important, but the great reforming social movements of the day. The crusade to make life healthier had many prongs: Temperance, regulation of the food chain, dietary guidelines, exercise (spread through the "muscular Christianity" Teddy Roosevelt espoused), the City Beautiful movement with its parks and tree plantings, the construction of sewers, chlorination of drinking water, the paving of streets, the draining of swamps, the banning of dubious patent medicines: in a word, Progressivism. Taken together it worked, and by 1900 life expectancy was up to 50 for all the rich western nations and has continued to rise.
The same is true for more recent health advances; penicillin was a fantastic discovery, but antibiotics only had an impact on our health because the US and then other governments spent billions to develop them, and the spread of health insurance made them affordable. The safety movement with its "intrusive" regulations has made cars, trains, and factory work much, much safer.
Johnson's article seems to be arguing against the straw man view that "science" made things better by itself, but nobody who knows any history thinks that. Modernity was always as much about organization as it was about science and technology. Steam locomotives were technologically amazing but they weren't much good without railroads, which were built using primitive hand-labor methods but made possible by modern political and business changes. Nineteenth-century sewers were no better than Roman sewers – in fact they were often worse – but they were built by the thousands of miles in every city, by politicians who cared about the health of their working class voters.
I sometimes say that modern Republicans are trying to bring back the Gilded Age, but it is important to remember that even the Gilded Age benefitted from a century of crusades for public improvement. Real Libertarians, and many Anarchists, want to go much farther back and strip away the protections our societies built up across the 1800s. They, and all the other people who want to smash things, should think harder about the precious legacy of caring for each other that we have built up, and on the fact that taken together these measures have doubled the length of our lives.