The flush toilet...... Along with the associated sewerage and wastewater treatment.
40% of the world's population today has no access to toilets, and in many countries, open defacation anywhere on the ground is the rule of the day.
The advent of large-scale use of the flush toilet circa 1900 or so added 20 years to the average human lifespan--in countries where sanitation is available.
I got this info by reading the "Look Inside" section of this book on Amazon.com:
http://www.amazon.com/Big-Necessity-Unmentionable-World-Matters/dp/0805082719/ref=cm_cr_pr_product_top#_
I think this title will be next up on my reading list when I finish my latest Kindle title.
Gosh I love ebooks.... I don't have a Kndle, but instead use the Kindle for PC software. I find myself Googling side topics as I learn new info from the books I read. It makes for a greater experience....
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