If you care about living a long, healthy life you should be thankful for the Industrial Revolution.
Writing in Scientific American Kevin Bonham (h/t Maggie's Farm) reminds us that innovations like soap and sanitation have been crucial in extending the length and quality of life:
Two of the most monumental developments in the history of human civilization, likely the innovations that have saved more human lives than any other, are soap and sanitation. When large numbers of people congregate in a single location for prolonged periods of time, excrement and waste quickly rise to unimaginable levels and are capable of spreading disease incredibly quickly. As I mentioned in my first post here at Food Matters, many pathogens utilize the fecal-oral transmission route, in which poop from an infected individual makes its way into the water supply or onto food by serial contact (touching a contaminated surface then touching food). Lack of hygiene dramatically increases the likelihood of this sort of infection, as many infectious microbes can grow unchecked on filth outside the body, and many viruses can linger on unwashed surfaces for long periods of time.
As always, we humans have a tendency to take things just a bit too far. Limiting our exposure to harmful pathogens is one thing; eliminating our exposure to them is quite another.
Cleanliness may be next to godliness, but no one is seriously suggesting that we should all live in a perfectly sterile environment.
Yet while there’s no doubt that sanitation and hygiene are critical in reducing the spread of infectious disease, it’s possible that we’ve gone too far in trying to live a sterile life.
In 1989, British physician David Strachan proposed the “Hygiene Hypothesis,” which sought to explain a puzzling series of observations: Children in cities in developed countries and had fewer siblings, those that lived more sanitary lives and presumably had less exposure to infectious diseases, were more likely to develop allergies, asthma and other atopic diseases than those that lived on farms or in developing countries, or that had many siblings. In the nearly 25 years since this was first proposed, a great deal of research has shown that exposure to diverse bacteria or even parasitic worms helps to train and regulate the immune system, preventing it from becoming over-active.
If your immune system is never exposed to dirt it will not develop effectively. If it is exposed to the wrong pathogens it will be overwhelmed.
Does this mean that the Japanese are wrong to prefer bowing to hugging? Does it mean that good manners are an evolutionary deficit? Not at all. Some exposure to germs is good for your immune system, but overexposure is certainly not. Why take unnecessary risks?
[Addendum: Princeton University has advised students not to share drinking cups, the better to avoid transmitting meningitis to their friends: http://www.nbcnews.com/id/53059616/ns/local_news-new_york_ny/#.UjxfPsakrWg]