Lot of important Roman technology, that affect quality of human life, was lost in dark times of Middle ages. For example sanitation systems:
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There is little record of other sanitation systems (apart from sanitation in ancient Rome) in most of Europe until the High Middle Ages. Unsanitary conditions and overcrowding were widespread throughout Europe and Asia during the Middle Ages. This resulted in pandemics such as the Plague of Justinian (541–542) and the Black Death (1347–1351), which killed tens of millions of people. Very high infant and child mortality prevailed in Europe throughout medieval times, due partly to deficiencies in sanitation.
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https://en.wikipedia.org/wiki/History_of_water_supply_and_sa...
Even today countries without technology for clean and safe drinking water and sanitation have big problems.
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Without better infrastructure and management, millions of people will continue to die each year from preventable, water-related diseases like malaria and diarrhea.
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https://www.un.org/sustainabledevelopment/water-and-sanitati...