Antibiotics and vaccines are nice, but nobody should sleep on how many children's lives are saved by proper rehydration therapy. Rotavirus isn't the scourge it used to be in most of the world.
Fun fact: the extremely high child mortality rates of the past contribute a lot to the deflation of life expectancy, meaning most people in medieval times actually didn't only live until 30 you either lived a long life or an extremely short one.
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Also, cool data